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The impact of bridging therapy (BT) on CD19-directed chimeric antigen receptor T-cell (CD19CAR-T) outcomes in large B-cell lymphoma (LBCL) is poorly characterised. Current practice is guided by physician preference rather than established evidence. Identification of effective BT modalities and factors predictive of response could improve CAR-T intention to treat and clinical outcomes. We assessed BT modality and response in 375 adult LBCL patients in relation to outcomes following axicabtagene ciloleucel (Axi-cel) or tisagenlecleucel (Tisa-cel). The majority of patients received BT with chemotherapy (57%) or radiotherapy (17%). We observed that BT was safe for patients, with minimal morbidity/mortality. We showed that complete or partial response to BT conferred a 42% reduction in disease progression and death following CD19CAR-T therapy. Multivariate analysis identified several factors associated with likelihood of response to BT, including response to last line therapy, the absence of bulky disease, and the use of Polatuzumab-containing chemotherapy regimens. Our data suggested that complete/partial response to BT may be more important for Tisa-cel than Axi-cel, as all Tisa-cel patients with less than partial response to BT experienced frank relapse within 12 months of CD19CAR-T infusion. In summary, BT in LBCL should be carefully planned towards optimal response and disease debulking, to improve CD19CAR-T patient outcomes. Polatuzumab-containing regimens should be strongly considered for all suitable patients, and failure to achieve complete/partial response to BT pre-Tisa-cel may prompt consideration of further lines of BT where possible.

Introduction: Patients (pts) with CLL may be at particular risk of severe COVID-19 given advanced age and immune dysregulation. Two large series with limited follow-up have reported outcomes for pts with CLL and COVID-19 (Scarfò, et al. Leukemia 2020; Mato, et al. Blood 2020). To provide maximal clarity on outcomes for pts with CLL and COVID-19, we partnered in a worldwide effort to describe the clinical experience and validate predictors of survival, including potential treatment effects. Methods: This international collaboration represents a partnership between investigators at 141 centers. Data are presented in two cohorts. Cohort 1 (Co1) includes pts captured through efforts by European Research Initiative on CLL (ERIC), Italian CAMPUS CLL Program, and Grupo Español de Leucemia Linfática Crónica. The validation cohort, Cohort 2 (Co2), includes pts from US (66%), UK (23%), EU (7%), and other countries (4%). There is no overlap in cases between cohorts. CLL pts were included if COVID-19 was diagnosed by PCR detection of SARS-CoV-2 and they required inpatient hospitalization. Data were collected retrospectively 2/2020 - 5/2020 using standardized case report forms. Baseline characteristics, preexisting comorbidities (including cumulative illness rating scale (CIRS) score ≥6 vs. The primary endpoint of this study was to estimate the case fatality rate (CFR), defined as the proportion of pts who died among all pts hospitalized with COVID-19. Chi-squared test was used to compare frequencies; univariable and multivariable analyses utilized Cox regression. Predictors of inferior OS in both Co1 and Co2 were included in multivariable analyses. Kaplan-Meier method was used to estimate overall survival (OS) from time of COVID-19 diagnosis (dx). Results: 411 hospitalized, COVID-19 positive CLL pts were analyzed (Co1 n=281, Co2 n=130). Table 1 describes baseline characteristics. At COVID-19 dx, median age was 72 in Co1 (range 37-94) and 68 in Co2 (range 41-98); 31% (Co1) and 45% (Co2) had CIRS ≥6. In Co1, 48% were treatment-naïve and 26% were receiving CLL-directed therapy at COVID-19 dx (66% BTKi ± anti-CD20, 19% Venetoclax ± anti-CD20, 9.6% chemo/chemoimmunotherapy (CIT), 1.4% PI3Ki, 4% other). In Co2, 36% were never treated and 49% were receiving CLL-directed therapy (65% BTKi ± anti-CD20, 19% Venetoclax ± anti-CD20, 9.4% multi-novel agent combinations, 1.6% CIT, 1.6% PI3Ki, 1.6% anti-CD20 monotherapy, 1.6% other). Most pts receiving CLL-directed therapy had it held at COVID-19 diagnosis (93% in Co1 and 81% in Co2). Frequency of most COVID-19 symptoms/laboratory abnormalities were similar in the two cohorts including fever (88% in both), lymphocytosis (ALC ≥30 x 109/L; 27% vs. 21%), and lymphocytopenia (ALC < 1.0 x 109/L; 18% vs. 28%), while others varied between Co1 and Co2 (p Median follow-up was 24 days (range 2-86) in Co1 and 17 days (1-43) in Co2. CFRs were similar in Co1 and Co2, 30% and 34% (p=0.45). 54% and 43% were discharged while 16% and 23% remained admitted at last follow-up in Co1 and Co2, respectively. The proportion of pts requiring supplemental oxygen was similar (89% vs. 92%) while rate of ICU admission was higher in Co2 (20% vs. 48%, p Conclusions : In the largest cancer dx-specific cohort reported, pts with CLL hospitalized for COVID-19 had a CFR of 30-34%. Advanced patient age at COVID-19 diagnosis was an independent predictor of OS in two large cohorts. This CFR will serve as a benchmark for mortality for future outcomes studies, including therapeutic interventions for COVID-19 in this population. The effect of CLL treatment on OS was inconsistent across cohorts; COVID-19 may be severe regardless of treatment status. While there were no significant differences in distribution of current lines of therapy between cohorts, prior chemo exposure was more common in Co1 vs. Co2, which may account for difference in OS. Extended follow-up will be presented. Disclosures Roeker: American Society of Hematology: Research Funding; Abbott Laboratories: Other: spouse with minority ownership interest ; AbbVie: Other: spouse with minority ownership interest . Scarfo:Janssen: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Abbvie: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; AstraZeneca: Honoraria; Gilead: Membership on an entity's Board of Directors or advisory committees. Abrisqueta:Celgene: Consultancy, Honoraria; Janssen: Consultancy, Honoraria, Speakers Bureau; Roche: Consultancy, Honoraria, Speakers Bureau; AbbVie: Consultancy, Honoraria, Speakers Bureau. Eyre:AbbVie: Consultancy, Honoraria, Other: travel support; Gilead: Consultancy, Honoraria, Other: travel support; Janssen: Consultancy, Honoraria, Other: travel support; KITE, AZ, Loxo Oncology at Lilly: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau. Muntañola Prat:Roche: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: travel grants; participated in advisory boards; Abbvie: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: travel grants; participated in advisory boards; Janssen: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: travel grants; participated in advisory boards. Villacampa:AstraZeneca: Other: advisory role; Merck Sharp & Dohme: Honoraria. Leslie:AstraZeneca: Consultancy, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Bayer: Consultancy, Membership on an entity's Board of Directors or advisory committees; ADC therapeutics: Consultancy, Membership on an entity's Board of Directors or advisory committees; AbbVie: Consultancy, Membership on an entity's Board of Directors or advisory committees; BeiGene: Speakers Bureau; KitePharma: Consultancy, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Celgene/BMS: Speakers Bureau; Seattle Genetics: Consultancy, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Pharmacyclics/Janssen: Consultancy, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Epizyme: Speakers Bureau; Karyopharm: Speakers Bureau; TG Therapeutics: Consultancy, Membership on an entity's Board of Directors or advisory committees. Allan:Acerta, Genentech, Abbvie, Sunesis, Ascentage, Pharmacyclics, Janssen, AstraZeneca, BeiGene: Consultancy; Celgene, Genentech, Janssen, TG Therapeutics: Research Funding; Abbvie, Janssen, AstraZeneca, Pharmacyclics: Honoraria. Furman:Incyte: Consultancy; Genentech: Consultancy; Sunesis: Consultancy; Pharmacyclics: Consultancy; Loxo Oncology: Consultancy; Oncotarget: Consultancy; Janssen: Consultancy, Speakers Bureau; TG Therapeutics: Consultancy, Research Funding; Abbvie: Consultancy; Beigene: Consultancy; AstraZeneca: Consultancy, Research Funding; Acerta: Consultancy; Verastem: Consultancy. Pagel:BeiGene, Astrazeneca, Loxo Oncology, Gilead: Consultancy. Hernandez-Rivas:Gilead: Membership on an entity's Board of Directors or advisory committees; Celgene/BMS: Membership on an entity's Board of Directors or advisory committees; Janssen: Membership on an entity's Board of Directors or advisory committees; Abbvie: Membership on an entity's Board of Directors or advisory committees; Roche: Membership on an entity's Board of Directors or advisory committees; AstraZeneca: Membership on an entity's Board of Directors or advisory committees; Rovi: Membership on an entity's Board of Directors or advisory committees. Patel:Genentech: Consultancy, Speakers Bureau; Adaptive Biotechnologies: Consultancy; Janssen: Consultancy, Speakers Bureau; Celgene/BMS: Consultancy, Membership on an entity's Board of Directors or advisory committees; BeiGene: Consultancy; Kite: Consultancy; Pharmacyclics: Consultancy, Speakers Bureau; AstraZeneca: Consultancy, Research Funding, Speakers Bureau. Motta:Roche: Honoraria; Janssen: Honoraria. Lamanna:AbbVie: Membership on an entity's Board of Directors or advisory committees, Research Funding; Pharmacyclics: Membership on an entity's Board of Directors or advisory committees; Gilead: Membership on an entity's Board of Directors or advisory committees, Research Funding; AstraZeneca: Membership on an entity's Board of Directors or advisory committees; Genentech: Research Funding; Verastem: Research Funding; Bei-Gene: Research Funding; TG Therapeutics: Research Funding; Acerta: Research Funding; Celgene: Membership on an entity's Board of Directors or advisory committees, Research Funding; Roche-Genentech: Membership on an entity's Board of Directors or advisory committees; Janssen: Membership on an entity's Board of Directors or advisory committees. Vitale:Janssen: Honoraria. Kamdar:Roche: Research Funding. Österborg:BeiGene: Research Funding; Kancera: Current equity holder in publicly-traded company, Research Funding; Sanofi: Consultancy; Karolinska Univeristy Hospital, Stockholm, Sweden: Current Employment. Hanson:Janssen-Cilag: Research Funding; Gilead: Research Funding; AbbVie: Honoraria. Eichhorst:ArQule: Consultancy, Honoraria, Other: travel support, Research Funding; BeiGene: Consultancy, Honoraria, Other: travel support, Research Funding; Gilead: Consultancy, Honoraria, Other: travel support, Research Funding; AstraZeneca: Consultancy, Honoraria, Other: travel support, Research Funding; Oxford Biomedica: Consultancy, Honoraria, Other: travel support, Research Funding; AbbVie: Consultancy, Honoraria, Other: travel support, Research Funding; F. Hoffmann-LaRoche: Consultancy, Honoraria, Other: travel support, Research Funding; Janssen-Cilag: Consultancy, Honoraria, Other: travel support, Research Funding; Celgene: Consultancy, Honoraria, Other: travel support, Research Funding; Novartis: Consultancy, Honoraria, Other: travel support, Research Funding. Reda:Gilead: Membership on an entity's Board of Directors or advisory committees; Janssen: Membership on an entity's Board of Directors or advisory committees; Abbvie: Membership on an entity's Board of Directors or advisory committees. Varettoni:Janssen: Consultancy, Membership on an entity's Board of Directors or advisory committees, Other: Travel/accommodations/expenses; AbbVie: Other: Travel/accommodations/expenses; Roche: Consultancy, Membership on an entity's Board of Directors or advisory committees. Marchetti:Gilead: Consultancy; Novartis: Speakers Bureau; Amgen: Speakers Bureau; AbbVie: Other: Sponsored meetings; Takeda: Other: Sponsored meetings; Pfeizer: Other: Sponsored meetings. Munir:F. Hoffmann-La Roche: Consultancy, Other: Medical writing support, furnished by Scott Battle, PhD, of Health Interactions, was funded by F. Hoffmann-La Roche Ltd, Basel, Switzerland; Alexion: Honoraria. Zabalza:Janssen: Honoraria, Other: travel grants; Roche: Other: travel grants; Novartis: Other: travel grants. Janssens:Amgen: Consultancy, Other: travel grants; speaker fees; Abbvie: Consultancy, Other: travel grants; speaker fees; Celgene: Consultancy, Other: travel grants; speaker fees; Janssen: Consultancy, Other: travel grants; speaker fees; Gilead: Consultancy, Other: travel grants; speaker fees; Novartis: Consultancy, Other: travel grants; speaker fees; Sanofi-Genzyme: Consultancy, Other: travel grants; speaker fees; Roche: Consultancy, Other: travel grants; speaker fees. Niemann:AstraZeneca: Honoraria, Research Funding; CSL Behring: Honoraria, Research Funding; Janssen: Honoraria, Research Funding; Sunesis: Honoraria, Research Funding; Abbvie: Honoraria, Research Funding; Danish Cancer Society: Honoraria, Research Funding; Novo Nordisk Foundation: Honoraria, Research Funding. Perini:Takeda: Honoraria; Janssen: Honoraria, Speakers Bureau; Abbvie: Speakers Bureau. Patten:AbbVie: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Roche: Consultancy, Honoraria; Novartis: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Janssen: Consultancy, Honoraria; Gilead: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Astra Zeneca: Honoraria. Marasca:Roche: Membership on an entity's Board of Directors or advisory committees; Abbvie: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Janssen: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Shire: Honoraria. Iyengar:Janssen: Honoraria; Gilead: Honoraria. Ferrari:Abbvie: Honoraria. El-Sharkawi:Roche: Other: Conference fees; Janssen: Honoraria, Membership on an entity's Board of Directors or advisory committees. Itchaki:Abbvie Inc: Consultancy, Research Funding. Ma:Novartis: Research Funding; Juno: Research Funding; Pharmacyclics, LLC, an AbbVie Company: Consultancy, Honoraria, Research Funding, Speakers Bureau; Kite: Consultancy, Honoraria; Janssen: Consultancy, Honoraria, Research Funding, Speakers Bureau; Gilead: Consultancy, Honoraria; Genentech: Consultancy, Honoraria; Bioverativ: Consultancy, Honoraria; BeiGene: Honoraria, Research Funding, Speakers Bureau; AstraZeneca: Consultancy, Honoraria, Research Funding, Speakers Bureau; AbbVie: Consultancy, Honoraria, Research Funding; TG Therapeutics: Research Funding. Van Der Spek:AMGEN: Other: Teaching activities. Seymour:Seattle Genetics: Research Funding; Merck: Research Funding; Karyopharm: Membership on an entity's Board of Directors or advisory committees, Research Funding; Janssen/Pharmacyclics: Membership on an entity's Board of Directors or advisory committees; Incyte: Research Funding; Genentech: Research Funding; Bristol-Myers Squibb: Research Funding. Rigolin:Gilead: Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Janssen: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Abbvie: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau. Mauro:Roche: Other; Octopharma: Other; Takeda-Shire: Other; Gilead: Other; Janssen: Other; Abbvie: Other. Laurenti:Janssen: Honoraria; Gilead: Honoraria; AbbVie: Honoraria; Roche: Honoraria. Levin:Janssen: Membership on an entity's Board of Directors or advisory committees, Other: travel compensation; Abbvie: Membership on an entity's Board of Directors or advisory committees, Other: travel compensation; Roche: Membership on an entity's Board of Directors or advisory committees, Other: travel compensation. Špaček:Gilead: Honoraria; Abbvie: Honoraria; Janssen: Honoraria. Walewska:AbbVie: Other: sponsored for educational meetings, Speakers Bureau; Janssen: Other: sponsored for educational meetings, Speakers Bureau; Gilead: Speakers Bureau; Astra Zeneca: Membership on an entity's Board of Directors or advisory committees. Wiestner:Pharmacyclics LLC, an AbbVie Company; Acerta, Merck, Nurix, Verastem, and Genmab: Research Funding; National Institutes of Health: Patents & Royalties: and other intellectual property. Broom:Gilead: Other: Travel support, Speakers Bureau. Kater:Abbvie: Research Funding; Roche: Research Funding; Janssen: Research Funding; Celgene: Research Funding; Genentech: Research Funding. Ujjani:AstraZeneca: Consultancy, Honoraria, Research Funding; Abbvie: Consultancy, Honoraria, Research Funding; Verastem Oncology: Consultancy, Honoraria; Gilead/Kite: Consultancy, Research Funding; Atara: Consultancy, Honoraria; Genentech: Consultancy, Honoraria; MorphoSys: Consultancy. Vandenberghe:Celgene: Other: sponsorship to attend Lugano lymphoma meeting in 2019; Gilead: Other: travel grants, Research Funding; Abbvie: Other: travel grants, Research Funding; Janssen: Other: travel grants; Roche: Other: travel grants, Research Funding. Chong:Novartis: Membership on an entity's Board of Directors or advisory committees; Tessa: Membership on an entity's Board of Directors or advisory committees; BMS: Membership on an entity's Board of Directors or advisory committees; KITE Pharma: Membership on an entity's Board of Directors or advisory committees. Pu:Takeda Pharmaceuticals: Consultancy. Brown:Janssen, Teva: Speakers Bureau; Gilead, Loxo, Sun, Verastem: Research Funding; Abbvie, Acerta, AstraZeneca, Beigene, Invectys, Juno/Celgene, Kite, Morphosys, Novartis, Octapharma, Pharmacyclics, Sunesis, TG Therapeutics, Verastem: Consultancy. Trentin:Janssen: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Abbvie: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Octapharma: Membership on an entity's Board of Directors or advisory committees; Takeda: Membership on an entity's Board of Directors or advisory committees; Shire: Honoraria. Farina:Abbvie: Membership on an entity's Board of Directors or advisory committees; Janssen: Membership on an entity's Board of Directors or advisory committees. Sanchez:Abbvie: Other: travel grants; Amgem: Other: travel grants; Janssen: Other: travel grants; Celgene: Other: travel grants; Roche: Other: travel grants. Shadman:Abbvie, Genentech, Astra Zeneca, Sound Biologics , Pharmacyclics, Verastem, ADC therapeutics, Beigene, Cellectar, BMS, Morphosys and Atara Biotherapeutics: Consultancy; Mustang Bio, Celgene, Pharmacyclics, Gilead, Genentech, Abbvie, TG therapeutics, Beigene, Astra Zeneca, Sunesis, Beigene: Research Funding. Foglietta:Janssen: Honoraria; Gilead: Honoraria. Jaksic:Roche: Honoraria; Janssen: Honoraria; Abbvie: Honoraria. Sportoletti:AbbVie: Honoraria; Janssen: Honoraria. Barr:Morphosys: Consultancy; Gilead: Consultancy; AstraZeneca: Consultancy, Research Funding; Verastem: Consultancy; Seattle Genetics: Consultancy; TG therapeutics: Consultancy, Research Funding; Abbvie/Pharmacyclics: Consultancy, Research Funding; Celgene: Consultancy; Merck: Consultancy; Genentech: Consultancy; Janssen: Consultancy. Ruchlemer:Abbvie Inc: Consultancy, Research Funding. Kersting:Celgene: Other: travel grant; Janssen: Research Funding; Abbvie: Research Funding. Huntington:Pharmacyclics: Honoraria; AbbVie: Consultancy; Novartis: Consultancy; Genentech: Consultancy; DTRM: Research Funding; Celgene: Consultancy, Research Funding; Bayer: Consultancy, Honoraria; Astrazeneca: Honoraria; TG Therapeutics: Research Funding. Herishanu:Roche: Honoraria; Sanofi: Honoraria; Medison: Honoraria; Janssen: Honoraria; Abbvie: Honoraria; AstraZeneca: Honoraria. Jacobs:TG Therapeutics, Inc.: Research Funding; Astra Zeneca: Consultancy, Speakers Bureau; AbbVie: Consultancy, Speakers Bureau; Pharmacyclics: Research Funding, Speakers Bureau; Seattle Genetics: Consultancy; Verastem: Consultancy; Janssen: Consultancy, Speakers Bureau; Genentech: Speakers Bureau; Sanofi Genzyme: Speakers Bureau. Portell:BeiGene: Consultancy, Research Funding; Pharmacyclics: Consultancy; TG Therapeutics: Research Funding; Infinity: Research Funding; Roche/Genentech: Consultancy, Research Funding; Xencor: Research Funding; Bayer: Consultancy; Amgen: Consultancy; Janssen: Consultancy; Kite: Consultancy, Research Funding; Acerta/AstraZeneca: Research Funding; AbbVie: Research Funding. Rambaldi:Sanofi: Honoraria, Other: TRAVEL, ACCOMMODATIONS, EXPENSES (paid by any for-profit health care company); Astellas: Honoraria, Other: TRAVEL, ACCOMMODATIONS, EXPENSES (paid by any for-profit health care company); BMS/Celgene: Honoraria, Other: TRAVEL, ACCOMMODATIONS, EXPENSES (paid by any for-profit health care company); University of Milan: Current Employment; Roche: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Support of parent study and funding of editorial support. Received travel support., Research Funding; Gilead: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel support from Gilead.; Amgen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: TRAVEL, ACCOMMODATIONS, EXPENSES (paid by any for-profit health care company). Research grant from Amgen Inc.; Omeros: Honoraria, Other: TRAVEL, ACCOMMODATIONS, EXPENSES (paid by any for-profit health care company); Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: TRAVEL, ACCOMMODATIONS, EXPENSES (paid by any for-profit health care company); Pfizer: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: TRAVEL, ACCOMMODATIONS, EXPENSES (paid by any for-profit health care company). Advisory board and speaker fees from Pfizer.. Brander:Verastem: Consultancy, Honoraria, Other, Research Funding; NCCN: Other; Novartis: Consultancy, Other; Teva: Consultancy, Honoraria; Tolero: Research Funding; NCCN: Other; Novartis: Consultancy, Other; Teva: Consultancy, Honoraria; Tolero: Research Funding; AbbVie: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other, Research Funding; ArQule: Consultancy, Other, Research Funding; Ascentage: Other, Research Funding; AstraZeneca: Consultancy, Honoraria, Other, Research Funding; BeiGene: Other, Research Funding; DTRM: Other, Research Funding; Genentech: Consultancy, Honoraria, Other, Research Funding; Juno/Celgene/BMS: Other, Research Funding; MEI Pharma: Other, Research Funding; Pharmacyclics LLC, an AbbVie Company: Consultancy, Honoraria, Other, Research Funding; Pfizer: Consultancy, Other; TG Therapeutics: Consultancy, Membership on an entity's Board of Directors or advisory committees, Other, Research Funding. Rossi:Abbvie: Membership on an entity's Board of Directors or advisory committees; Daiichi Sankyo: Consultancy, Honoraria; Celgene: Membership on an entity's Board of Directors or advisory committees; Jazz: Membership on an entity's Board of Directors or advisory committees; Janssen: Membership on an entity's Board of Directors or advisory committees; Novartis: Other: Advisory board; Astellas: Membership on an entity's Board of Directors or advisory committees; Amgen: Honoraria; Pfizer: Membership on an entity's Board of Directors or advisory committees; Alexion: Membership on an entity's Board of Directors or advisory committees; Sanofi: Honoraria; Takeda: Honoraria, Membership on an entity's Board of Directors or advisory committees. Coscia:Karyopharm Therapeutics: Research Funding; Gilead: Honoraria, Membership on an entity's Board of Directors or advisory committees; Shire: Honoraria, Membership on an entity's Board of Directors or advisory committees; Janssen: Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Abbvie: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau. Coombs:Abbvie: Consultancy, Honoraria; Genentech: Honoraria; AstraZeneca: Honoraria; MEI Pharma: Honoraria; LOXO Oncology: Honoraria; Octapharma: Honoraria; Novartis: Honoraria. Schuster:Novartis, Genentech, Inc./ F. Hoffmann-La Roche: Research Funding; AlloGene, AstraZeneca, BeiGene, Genentech, Inc./ F. Hoffmann-La Roche, Juno/Celgene, Loxo Oncology, Nordic Nanovector, Novartis, Tessa Therapeutics: Consultancy, Honoraria. Foà:Abbvie: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Roche: Membership on an entity's Board of Directors or advisory committees; Novartis: Speakers Bureau; Roche: Membership on an entity's Board of Directors or advisory committees; Incyte: Speakers Bureau; Janssen: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau. Cuneo:Astra Zeneca: Honoraria; Gilead: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Roche: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Abbvie: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Janssen: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau. Bosch:Jansen: Honoraria; Abbvie: Honoraria; Novartis: Honoraria; Astra Zeneca: Honoraria; Takeda: Honoraria; Celgene: Honoraria; Roche: Honoraria. Stamatopoulos:AstraZeneca: Honoraria; Janssen, Gilead, Abbvie: Honoraria, Research Funding. Ghia:Adaptive, Dynamo: Consultancy, Honoraria; Novartis: Research Funding; BeiGene: Consultancy, Honoraria; Janssen: Consultancy, Honoraria, Other: TRAVEL, ACCOMMODATIONS, EXPENSES (paid by any for-profit health care company), Research Funding; Celgene/Juno: Consultancy, Honoraria; Lilly: Consultancy, Honoraria; MEI: Consultancy, Honoraria; Sunesis: Consultancy, Honoraria, Research Funding; AbbVie: Consultancy, Honoraria, Other: TRAVEL, ACCOMMODATIONS, EXPENSES (paid by any for-profit health care company), Research Funding; Gilead: Consultancy, Honoraria, Research Funding; ArQule: Consultancy, Honoraria; Acerta/AstraZeneca: Consultancy, Honoraria. Mato:Adaptive: Consultancy, Research Funding; Janssen: Consultancy, Research Funding; AbbVie: Consultancy, Research Funding; BeiGene: Consultancy; LOXO: Consultancy, Research Funding; Genentech: Consultancy, Research Funding; AstraZeneca: Consultancy, Research Funding; Pharmacyclics LLC, an AbbVie Company: Consultancy, Research Funding; TG Therapeutics: Consultancy, Other: DSMB, Research Funding.

Background: In the treatment of advanced Hodgkin lymphoma, it is increasingly common UK practice to modify escalated BEACOPP (eBPP) by removing oral procarbazine and replacing it with intravenous dacarbazine (250mg/m2 D2-3) to reduce haematopoietic stem cell and gonadal toxicity. However, published data of the "escalated BEACOPDac (eBPDac)" regimen are very limited. Methods: This is a retrospective study of 225 patients from 20 centres in the UK, Ireland and France who were treated with eBPDac first line for advanced stage Hodgkin Lymphoma. Toxicity outcomes were compared with 58 matched patients treated with eBPP at 4 UK centres and survival outcomes were compared with 2073 eBPP patients in the HD18 trial 1 and with 1088 patients aged 18-59y in the RATHL trial 2,3. Most eBPDac patients were treated as per HD18 protocol. The 34 patients treated in Paris followed the AHL2011 protocol with two courses of eBPDac given upfront and if iPET2 negative were deescalated to 4 cycles of ABVD. Toxicity outcomes: Toxicity was compared between eBPDac patients (n=225; median follow-up 22.1 months) and matched real-world UK eBPP patients (n=58; median follow-up 52.7 months) over the first 4 cycles. eBPP and eBPDac patients were well matched with no significant differences in age (median 23 y vs 26 y), sex, stage (stage 3/4 82% vs 83%) and international prognostic score (IPS 3+ 74% vs 65%). 55% of eBPDac patients received only 4 cycles (vs 12% of eBPP patients; p Disease outcomes: The eBPDac patients (n=225) were younger than the HD18 patients (median age 26 y vs 35 y, p Figure 1 shows Kaplan-Meier plots for progression-free survival (PFS) and overall survival (OS). The PFS at 22 months (median follow-up) of eBPDac patients was 94.9% (91.7-98.3%) which is similar to HD18 3 year PFS of 92.3% (91.1-93.5%) and appears superior to RATHL 5 year PFS 81.4% (78.9-83.7%). The difference in PFS between eBPDac and RATHL is most marked in IPS3+ patients. The OS rates with all 3 regimens are excellent, with 22 month eBPDac OS estimate of 98.9% (97.4-100%). Summary/Conclusion: Accepting the limitations of a retrospective study, we suggest that substituting dacarbazine for procarbazine is unlikely to compromise the efficacy of eBPP and may have some toxicity benefits. Despite the clear preference of clinicians to offer this regimen to high-risk advanced stage patients, with nearly 2 years median follow-up we have observed similar PFS and OS compared to HD18 but superior survival estimates compared with 18-59y RATHL patients, suggesting that eBPDac is highly efficacious for the treatment of Hodgkin lymphoma. References: 1Borchmann P et al. Lancet 2017; 390:2790-2802 2Johnson P et al. NEJM. 2016; 374:2419-2429 3Russell J et al. Ann Hematol 2021; 100:1049-1058 Figure 1 Figure 1. Disclosures Brice: MSD: Research Funding; Amgen: Other: Travel/accommodations/expenses; Roche: Other: Travel/accommodations/expenses; Takeda: Research Funding. Menne: Kite/Gilead: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel grant, Research Funding, Speakers Bureau; Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Janssen: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel grants; Amgen: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel grants; Astra Zeneca: Research Funding; Jazz: Other: Travel grants; Pfizer: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel grants; Bayer: Other: Travel grants; Kyowa Kirin: Other: Travel grants; Daiichi Sankyo: Honoraria, Membership on an entity's Board of Directors or advisory committees; Atara: Honoraria, Membership on an entity's Board of Directors or advisory committees; Takeda: Other: Honoraria for Lectures; Roche: Other: Honoraria for Lectures. Osborne: Roche: Other; Takeda: Other; Pfizer: Other; Servier: Other; Gilead: Other; Novartis: Other; MSD: Other. Ardeshna: Gilead, Beigene, Celegene, Novartis and Roche: Membership on an entity's Board of Directors or advisory committees; Gilead, Beigene, Celegene, Novartis and Roche: Honoraria; Norvartis, BMS, Autolus, ADCT, Pharmocyclics and Jansen: Research Funding. Collins: Pfizer: Honoraria; Amgen: Research Funding; AstraZeneca: Honoraria, Research Funding; Beigene: Membership on an entity's Board of Directors or advisory committees; Novartis: Honoraria, Speakers Bureau; Celgene: Research Funding; ADC Therapeutics: Honoraria, Membership on an entity's Board of Directors or advisory committees; Celleron: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Merck Sharp & Dohme: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Bristol Myers Squibb: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Gilead: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Takeda: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Roche: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel expenses, Speakers Bureau. Cwynarski: Adienne, Takeda, Roche, Autolus, KITE, Gilead, Celgene, Atara, Janssenen: Other. Davies: Janssen: Honoraria, Research Funding; Karyopharm Therapeutics: Membership on an entity's Board of Directors or advisory committees, Research Funding; Acerta Pharma/AstraZeneca: Honoraria, Research Funding; ADC Therapeutics: Honoraria, Research Funding; BioInvent: Research Funding; Incyte: Membership on an entity's Board of Directors or advisory committees; Kite: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Roche: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: travel to scientific conferences, Research Funding; Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: travel to scientific conferences, Research Funding. Furtado: Abbvie: Other: Conference support. Gallop-Evans: Takeda: Membership on an entity's Board of Directors or advisory committees; Kyowa-Kirin: Membership on an entity's Board of Directors or advisory committees. Iyengar: Gilead: Membership on an entity's Board of Directors or advisory committees, Other: conference support, Speakers Bureau; Takeda: Membership on an entity's Board of Directors or advisory committees, Other: conference support, Speakers Bureau; Beigene: Membership on an entity's Board of Directors or advisory committees; Abbvie: Other: conference support; Janssen: Other: conference support, Speakers Bureau. Linton: Roche: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Aptitude Health: Honoraria; Hartley Taylor: Honoraria; University of Manchester: Current Employment; Celgene: Research Funding; BeiGene: Research Funding; Genmab: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding. Martinez-Calle: Abbvie: Other. McKay: Roche: Honoraria, Membership on an entity's Board of Directors or advisory committees; Gilead: Honoraria, Other: Travel Support; KITE: Honoraria, Membership on an entity's Board of Directors or advisory committees; Takeda: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel Support; Janssen: Honoraria, Other: Travel Support; Beigene: Honoraria, Membership on an entity's Board of Directors or advisory committees; BMS/Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees. Nagumantry: Takeda, Alexion, Abbvie: Other. Shah: Abbvie, Janssen and Roche: Honoraria, Membership on an entity's Board of Directors or advisory committees. Uttenthal: Jazz: Other; Takeda: Other; Roche: Other. McMillan: Pfizer: Research Funding; F. Hoffmann-La Roche Ltd: Consultancy, Honoraria, Speakers Bureau; Amgen: Membership on an entity's Board of Directors or advisory committees; Abvie: Membership on an entity's Board of Directors or advisory committees. Follows: Janssen, Abvie, Roche, AZ: Other.

Introduction Breast implant-associated anaplastic large cell lymphoma (BIA-ALCL) is a T-cell lymphoma associated with textured breast implants, recently recognized by the revised WHO Classification. Recommended management for BIA-ALCL involves a multidisciplinary team (MDT) approach with breast surgery, haemato-oncology, pathology, radiology and oncoplastic input. Definitive management for the 'effusion-only' subset is surgical implant and capsule removal; systemic therapy is reserved for 'mass-forming' and 'advanced-disease' cohorts. Overall prognosis is excellent with the vast majority achieving remission. Although the diagnostic and treatment paradigm is established, post treatment surveillance and follow-up guidance varies widely (globally); over-utilisation of imaging tests compromises the patient pathway, impacts limited health-care resources and is associated financial burdens on patients and providers. Recently, newly published consensus guidelines (UK MHRA and USA NCCN clarify follow-up and surveillance imaging (Table 1). The aim of this study was to review our BIA-ALCL specialist centre institutional practise; to quantify the direct economic cost (EC) of imaging surveillance and indirect EC of outpatient clinic (OPC) assessment compared EC if recent guidelines were followed. The secondary aim is to highlight and raise awareness of the latest international guidance to promote the standardisation of practise. Methods A retrospective analysis of a prospectively maintained patient database between July 2015 to October 2019 was conducted, with Institutional Review Board Approval. Data collection included patient demographics, tumour subset, treatment, clinical and imaging surveillance. Follow-up and imaging undertaken for symptomatic concerns / non-BIA-ALCL related pathology was excluded. Imaging costs were calculated using UK NHS tariffs. Results Eleven patients were treated for BIA-ALCL during the study period, with a median age of 49 at diagnosis (range 30-82years). Patients were diagnosed with: effusion-only (n=7), effusion and mass (n=2), mass-only (n=2) subtypes, at a median time of eleven years from implant insertion (IQR 8-12). All patients underwent explantation and en-bloc capsulectomy, with 1 patient required neo-adjuvant (CHOP, Brentuximab) and 1 adjuvant (CHOP) therapy (CHOP. Surveillance with imaging and OPC detected no disease recurrence to date (overall median follow-up 38 months, IQR 12-47). Post treatment episodes of surveillance imaging or follow-up related to patient symptoms were excluded. 8 patients underwent surveillance imaging at our institute (Table 2). Total cost of imaging was £10,396 ($14,396) with a median cost of £1,953 ($2,705) per patient [IQR £526-2029 ($728-2,810)]. 7 patients had completed at least 24 months follow-up since surgery during the study period (Table 3), with 3 patients having not yet completed their follow-up period of two years. Of those with completed follow-up, the median OPC follow-up per patient was 48 months (IQR 38-52), median number of OPC was 7 (IQR 6-11) and the median cost of clinic review was £982 (IQR 804-1395). The surplus cost per patient compared with recommended follow-up was £118 ($164) [IQR £0-531 ($0-738)]. Conclusions Our data shows the variable BIA-ALCL surveillance practise pattern and the associated additional direct and indirect EC of unnecessary asymptomatic surveillance imaging, with an excessive number of follow-up OPC and period of clinical follow-up after complete remission. With no recurrence detected in our patient cohort to date, this data supports the new UK and updated USA NCCN Guidelines (extrapolated from data in other NHLs, and analogous to principles of the ASH Choosing Wisely Campaign) that routine post-treatment surveillance imaging should not be performed in BIA-ALCL patients. Routine asymptomatic post-treatment surveillance imaging is clinically unnecessary and potentially leads to a 'Cascade Effect' of further tests, with increased radiation exposure, excess costs and impact on limited health-care resources. We also support open-access follow-up for patients in remission, to reduce unnecessary follow up appointments. With UK and USA guidelines now available for BIA-ALCL, we support training and education of health-care professionals, global consensus guidelines and a registry, for this rare however increasingly recognised new entity. Figure 1 Figure 1. Disclosures Iyengar: Takeda: Membership on an entity's Board of Directors or advisory committees, Other: conference support, Speakers Bureau; Gilead: Membership on an entity's Board of Directors or advisory committees, Other: conference support, Speakers Bureau; Beigene: Membership on an entity's Board of Directors or advisory committees; Abbvie: Other: conference support; Janssen: Other: conference support, Speakers Bureau. Nicholson: Pfizer: Consultancy; Kite, a Gilead Company: Other: Conference fees, Speakers Bureau; BMS/Celgene: Consultancy; Novartis: Consultancy, Other: Conference fees. El-Sharkawi: Kyowa Kirin: Other: Ad boards; Beigene: Other: Ad boards; ASTEX: Other: Ad boards; Novartis: Other: Travel Support; Takeda: Honoraria; Roche: Honoraria; Janssen: Honoraria, Other: Ad boards; AstraZeneca: Honoraria, Other: Ad boards; AbbVie: Honoraria, Other: Travel Support, Ad boards. Tasoulis: BMJ: Consultancy, Membership on an entity's Board of Directors or advisory committees. Cunningham: Roche: Research Funding; Clovis Oncology: Research Funding; Celgene: Research Funding; Eli Lilly: Research Funding; Bayer: Research Funding; OVIBIO: Membership on an entity's Board of Directors or advisory committees; 4SC: Research Funding; AstraZeneca: Research Funding; MedImmune: Research Funding.

AVENuE - Avelumab in the frontline treatment of advanced classic Hodgkin lymphoma - a window study Background Response adapted ABVD (doxorubicin, bleomycin, vinblastine, dacarbazine) has become a standard of care in many countries for advanced stage classic Hodgkin Lymphoma (cHL), as investigated in the RATHL study: following 2 cycles of ABVD patients with negative (Deauville 1-3) interim PET (iPET2) proceeded to 4 cycles of AVD; those with positive (Deauville 4-5) iPET2 intensified therapy to escalated bleomycin, etoposide, doxorubicin, cyclophosphamide, vincristine, procarbazine, prednisolone (escBEACOPP) or BEACOPP every 14 days. Overall this strategy was associated with a 3-year progression free survival (PFS) of 82.6%, and outcomes for patients with positive iPET2 were disappointing with 3y progression-free survival (PFS) of 67.5%. More intensive treatment such as upfront use of escBEACOPP has been reported to produce higher PFS (89% at 5 years), but it is unclear whether overall survival (OS) is improved. More intensive treatment is, however, associated with higher risk of toxicity. Inhibitors of programmed cell death protein 1 (PD-1) or programmed death-ligand 1 (PD-L1) have established efficacy in relapsed / refractory cHL with response rates of 55-87%. In the front line setting PD-1 inhibitors have a reported complete metabolic response (CMR) rate of 18-37%. Response to PD-L1 inhibitors in the frontline setting has not been explored. Serial serum TARC (thymus and activation-regulated chemokine) is reported to be prognostic in the frontline treatment of cHL and may aid response assessment because PET interpretation with checkpoint inhibitors is often complex. In the context of PD-1 inhibition, PD-1 expression by immunohistochemistry (IHC) and 9p24.1 copy gain by fluorescence in situ hybridisation (FISH) are reported to correlate with response. Methods AVENuE is a Phase II single-arm multicentre study with sites in the UK and Australia assessing the safety and efficacy of 2 cycles (4 doses) of the PD-L1 inhibitor avelumab for untreated high-risk stage II-IV cHL prior to the iPET2 response adapted approach described above. Eligible patients must be 16-60 years, ECOG 0-1, and have adequate organ function. Patients with; compressive symptoms from lymphoma, autoimmune disorders or immunosuppressive treatment within 2 months are excluded. The primary endpoint is the centrally reviewed PET CMR rate to avelumab. Secondary endpoints are: the safety and tolerability of sequential avelumab and combination chemotherapy as assessed by CTCAE v 5.0; the iPET2 CMR rate after avelumab and 2 cycles of ABVD; PFS and OS at one year. Using a single stage A'hern design, target recruitment is 47 patients to give 90% power at a 0.05% one sided alpha to exclude an overall response rate (ORR) to 2 cycles of avelumab of < 20%; an ORR of 40% would be considered worthy of further study. Recruitment has continued during the COVID-19 pandemic. 29 patients have been enrolled. Exploratory endpoints include correlating disease response with baseline PD-1 copy number by FISH and PD-1 expression by IHC. Serial serum TARC is being explored as an aid to response assessment and changes in peripheral blood immune cell subset are being investigated as possible biomarkers of response. Trial funder: Pfizer Ltd in alliance with Merck KGaA Pfizer Ltd is providing funding as part of an Alliance between Pfizer and Merck KGaA Clinical trials.gov NCT03617666 EUDRACT No.: 2018-002227-42 Disclosures Hawkes: Roche: Membership on an entity's Board of Directors or advisory committees, Other: Travel and accommodation expenses, Research Funding, Speakers Bureau; Regeneron: Speakers Bureau; Merck KgA: Research Funding; Astra Zeneca: Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Janssen: Speakers Bureau; Merck Sharpe Dohme: Membership on an entity's Board of Directors or advisory committees; Novartis: Membership on an entity's Board of Directors or advisory committees; Gilead: Membership on an entity's Board of Directors or advisory committees; Antigene: Membership on an entity's Board of Directors or advisory committees; Bristol Myers Squib/Celgene: Membership on an entity's Board of Directors or advisory committees, Research Funding; Specialised Therapeutics: Consultancy. Barrington: Bristol Myers Squibb international corporation: Research Funding; Pfizer Inc: Research Funding; Amgen Ltd: Research Funding; Takeda Speakers Bureau: Honoraria. McKay: Roche: Honoraria, Membership on an entity's Board of Directors or advisory committees; Gilead: Honoraria, Other: Travel Support; KITE: Honoraria, Membership on an entity's Board of Directors or advisory committees; Takeda: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel Support; Janssen: Honoraria, Other: Travel Support; Beigene: Honoraria, Membership on an entity's Board of Directors or advisory committees; BMS/Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees. Iyengar: Janssen: Other: conference support, Speakers Bureau; Abbvie: Other: conference support; Beigene: Membership on an entity's Board of Directors or advisory committees; Gilead: Membership on an entity's Board of Directors or advisory committees, Other: conference support, Speakers Bureau; Takeda: Membership on an entity's Board of Directors or advisory committees, Other: conference support, Speakers Bureau. Radford: Takeda: Consultancy, Honoraria, Research Funding, Speakers Bureau; AstraZeneca: Current holder of individual stocks in a privately-held company; ADC Therapeutics: Consultancy, Current holder of individual stocks in a privately-held company, Honoraria, Speakers Bureau; BMS: Honoraria. Shah: Abbvie, Janssen and Roche: Honoraria, Membership on an entity's Board of Directors or advisory committees. Clifton-Hadley: Bristol-Myers Squibb Pharmaceuticals Ltd..: Other: The haematology team at the CTC has received funding (which in part pays staff salary) to Sponsor and coordinate clinical trials.; Amgen: Other: The haematology team at the CTC has received funding (which in part pays staff salary) to Sponsor and coordinate clinical trials.; Celgene: Other: The haematology team at the CTC has received funding (which in part pays staff salary) to Sponsor and coordinate clinical trials.; Merck Sharp and Dohme: Other: The haematology team at the CTC has received funding (which in part pays staff salary) to Sponsor and coordinate clinical trials.; Janssen-Cilag: Other: The haematology team at the CTC has received funding (which in part pays staff salary) to Sponsor and coordinate clinical trials.; Pfizer: Other: The haematology team at the CTC has received funding (which in part pays staff salary) to Sponsor and coordinate clinical trials.; Millennium pharmaceutics inc.: Other: The haematology team at the CTC has received funding (which in part pays staff salary) to Sponsor and coordinate clinical trials.. Collins: Beigene: Membership on an entity's Board of Directors or advisory committees; Novartis: Honoraria, Speakers Bureau; Pfizer: Honoraria; Celgene: Research Funding; Amgen: Research Funding; AstraZeneca: Honoraria, Research Funding; ADC Therapeutics: Honoraria, Membership on an entity's Board of Directors or advisory committees; Celleron: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Merck Sharp & Dohme: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Bristol Myers Squibb: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Gilead: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Takeda: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Roche: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel expenses, Speakers Bureau. OffLabel Disclosure: Avelumab prior to frontline chemotherapy in advanced stage classic Hodgkin lymphoma.

Introduction Following completion of chemotherapy with curative intent for DLBCL, for those in remission (CR), numerous national and international guidelines suggest on-going follow-up primarily to detect relapse of disease. For example, the NCCN guidelines suggest that clinical history, examination and blood investigations should be performed every 3-6 months for 5 years and as clinically indicated thereafter. This is essentially a "screening programme" for an at-risk population that continues based on historical routine rather than due to evidence it is of benefit to the patient. Numerous papers have been published suggesting that routine surveillance scans or bloods such as LDH are not useful in this setting. We sought to analyse whether the screening procedures that are performed in the follow-up setting are useful in the detection of relapse in patients followed up in a single centre. Uniquely, we examined each time point separately rather than group all follow-up events together. Methods Data was obtained retrospectively from electronic patient records for all patients in remission following treatment with frontline chemotherapy for DLBCL at the Royal Marsden Hospital between 2005-2016. Screening assessments analysed were symptoms check, clinical examination, LDH >upper limit of normal, lymphocyte: monocyte ratio (LMR) Results Complete data from 262 patients who achieved a CR and were followed up was available. Median age was 63 years (17-94) with 59 patients with stage 1 disease, and 100 with stage 4 disease. The relapse rate was 59/261 (23%), with a median time to relapse of 13 months (2-120). Of the 59, 52 had symptoms they had noted prior to clinic, of whom 28 requested an early appointment to clinic and 22 waited until their routine clinic appointment or sought advice from other health professionals initially. Only 7 patients were picked up only on investigations performed at the hospital, 1 with hypercalcemia and 6 on routine scan with no symptoms, 3 at 3-6months, 2 and 9-12months and 1 at 12-18 months. Of these, 4/7 patients achieved a CR with subsequent therapy. The remaining 202 patients had 2853 clinic appointments, median number per patient 13 (1-44). The negative predictive value of clinical history, examination, LDH, LMR and CT scan was consistently very high (>90%) at all time points. However, the positive predictive value was low for symptoms, 0-35% with the higher values being in the first year. Clinical examination had better PPV due to fewer positive results, including both true and false. LDH and LMR were associated with a poor PPV at all time points. PPV for CT scans was variable (Table 1). Conclusions The "screening" of patients who are in remission from DLBCL requires considerable health resources and cost and also leads to increased exposure of the patient to hospitals which during the COVID-19 pandemic is being discouraged. Likelihood of relapse (which decreases with time) has an impact on the effectiveness of a screening programme, the relapse rate in this cohort was 23% in keeping with other published data. Importantly, the majority of patients had symptoms suggestive of relapse and so the screening was not required. In the few that were asymptomatic when relapse was diagnosed, there was insufficient data to know whether this earlier detection led to a better outcome, however this has not been seen in other published cohorts. Finally the effectiveness of the screening is dependent on the predictive value of the "tests" being used and this dataset shows that whilst the negative predictive value is high, the positive predictive value is very variable and generally poor for all tools used. We propose that educating the patient regarding symptoms of relapse and having patient directed clinical follow-up rather than routine appointments would lead to marked savings in health resources, reduce hospital exposure of patients by eliminating unnecessary visits without compromising the outcome of the patients. Disclosures Cunningham: Lilly: Research Funding; MedImmune: Research Funding; Merck: Research Funding; AstraZeneca: Research Funding; Celgene: Research Funding; Bayer: Research Funding; Janssen: Research Funding; Merrimack: Research Funding; Amgen: Research Funding; 4SC: Research Funding; Clovis Oncology: Research Funding; Sanofi: Research Funding; OVIBIO: Membership on an entity's Board of Directors or advisory committees. Iyengar:Beigene: Consultancy; Janssen: Honoraria; Abbvie: Honoraria; Takeda: Consultancy, Honoraria, Speakers Bureau; Gilead: Consultancy, Honoraria, Speakers Bureau. El-Sharkawi:Abbvie: Consultancy, Honoraria, Speakers Bureau; AstraZeneca: Consultancy, Honoraria, Speakers Bureau; Janssen: Consultancy, Speakers Bureau; Takeda: Honoraria, Speakers Bureau; Innate: Consultancy.

Introduction: Patients with leukemic indolent B-cell Non-Hodgkin Lymphomas (LI B-NHL) that do not easily fall into a distinct pathological category with standard diagnostics can pose a challenge as their optimal management is uncertain. Lack of a clear diagnostic label can deny patients access to novel therapies as regulatory approval of drugs is largely granted within histological categories. Moreover, these patients may be excluded from participation in clinical trials. We report findings from a prospective study evaluating targeted next generation sequencing (NGS) of circulating malignant B-cells in this setting. Methods: Over a period of 4 years, 108 patients with LI B-NHL, deemed unclassifiable on standard peripheral blood (PB) diagnostics, were prospectively enrolled from 14 centres around the UK including ours. Patients with non-clonal lymphocytosis, confirmed CLL-type MBL, CLL (Matutes score 4 or 5), MCL, HCL, high grade lymphoma on standard PB diagnostics were excluded. Clinical and morphological characteristics were analysed. PB immunophenotyping was used for characterisation including ROR1 expression. CD15+ cells were positively selected with magnetic beads for germline DNA. Tumor-germline pairs were analysed with theEuroclonality-NGS DNA capture panel, and ARResT/Interrogate and complementary pipelines, to characterise clonal immunoglobulin rearrangements, translocations and somatic mutations (Stewart et al. ASH annual meeting 2019). Germline variants were subtracted to improve somatic mutation detection. Results: Median age was 72yrs with M:F ratio of 2:1. Incidental lymphocytosis on a routine blood count was the commonest mode of presentation with only a third of patients symptomatic at presentation. Median lymphocyte count was 12.4 x 109/L at the time of sampling. Just under 50% of cases had partial or complete CD5 expression, CD19 and 20 expression was moderate to strong in most cases while ROR1 was negative in most cases. NGS was able to assign a diagnostic category in 11/90 (12%) cases based on detection of IGH;CCND1 (6), IGH;BCL2 (2), IGH;BCL3 (2) translocations and in one case a BRAF mutation with confirmation of hairy cell leukaemia on immuno-morphology. These tests were not triggered by standard diagnostic pathways at initial presentation. Two novel translocations of uncertain significance were detected - RAD51B:BIRC3 and IGHMswitch-MICALL2/INTS1. Clonal IGHV-IGHD-IGHJ rearrangements were detected by NGS and/or Sanger sequencing with predominantly IGHV3 and IGHV4 gene usage, IGHV4-34 being the most common with 15 cases. The majority of rearrangements showed somatic hypermutations above 2% and none could be assigned to the 19 major CLL-associated stereotyped subsets (using ARResT/AssignSubsets). Somatic mutations were detected in 74/108 cases. The most frequently mutated genes were TP53 in 16/108 (15%) and the hotspot MYD88 L265P mutation in 14/108 (13%) with VAF of 20-46%. Other variants detected were distributed among genes associated with NFkB signalling and chromatin remodelling (Figure 1). The MYD88 L265P mutation was present in a fifth of cases with mutations detected (14/74) and was the sole change seen in 7 cases. Accompanying mutations in the remaining cases included CD79B (2), POT1 (1), NFKBIE (1). No concomitant CXCR4 mutations were detected. Median age of the MYD88 L265P cohort was 68 years with male predominance (M:F=10:4). 9/14 presented with an incidental lymphocytosis and median count of 11.18 x 109/L. Lymphadenopathy was present in 3/14 (21%) while 7/14 (50%) had splenomegaly. A paraprotein was detected in 6/14 cases (4 IgM, 1 IgG, 1 IgA). CD5 was expressed in 6/14 cases by flow cytometry. CD19 and 20 were uniformly positive, CD79b was variable and 12/14 cases tested did not express ROR1. Conclusion: This prospective study outlines the value of a targeted NGS panel in enhancing the diagnosis of unclassifiable LI B-NHL thereby improving patient access to novel therapies and clinical trials. It highlights recurrent MYD88 mutations in a subset of patients that have splenomegaly as a frequent feature. 5 year clinical follow up data, currently being gathered in both the MYD88 mutated and overall cohort, will be valuable in further characterisation and risk stratification to inform management of these patients. Disclosures Furtado: Abbvie: Other: Conference Support. El-Sharkawi:Abbvie: Consultancy, Honoraria, Speakers Bureau; AstraZeneca: Consultancy, Honoraria, Speakers Bureau; Janssen: Consultancy, Speakers Bureau; Takeda: Honoraria, Speakers Bureau; Innate: Consultancy. Iyengar:Abbvie: Honoraria; Gilead: Consultancy, Honoraria, Speakers Bureau; Takeda: Consultancy, Honoraria, Speakers Bureau; Janssen: Honoraria; Beigene: Consultancy.

BACKGROUND: T-cell prolymphocytic leukemia (T-PLL) is a rare, aggressive, post thymic lymphoid malignancy, with an incidence of approximately 0.1/100,000 people. T-PLL accounts for ~2% of all mature lymphocytic leukaemias in adults >30 years. Median overall survival (OS) ~20 months and long term remissions are infrequent. Intravenous alemtuzumab, a monoclonal antibody directed against CD52 remains the most effective treatment in T-PLL. At the Royal Marsden Hospital (RMH) we have been using alemtuzumab for T-PLL since the early 1990s. We describe our experience over the last 3 decades. METHODS: We included 174 T-PLL patients that were diagnosed or treated at RMH between 1989-2019. Immunophenotyping data was available through our hematological malignancy diagnostic service (HMDS) from 1998 onwards. Kaplan-Meier analysis was used for OS and disease free interval (DFI) RESULTS: There were 174 patients in total. Mean age at diagnosis was 61 years old (range 32-88) and M: F ratio was ~2:1 (113:61). 90 patients had reliable information on complete blood count (CBC) at diagnosis with median white blood cell count of 74 x 109/L (range 10-918), median hemoglobin 126 g/L (range 59-175) and median platelet count 116 x 109/L (range 7-513). Sufficient immunophenotyping data was available for analysis in 135/174 patients. The results showed predictably high expression of CD2, CD3, CD5, CD7, CD52 and TCRαβ. CD25 was positive in 67/135 (50%) of cases which is higher than the 18-35% seen in the current literature. CD4+/CD8- cases comprised 83/135 (61%) with CD4-/CD8+ 19/135 (14%), CD4+/CD8+ 32/135 (23%) and CD4-/CD8- 2/135 (2%). These results are summarized in table 1. Karyotyping/FISH (fluorescent in-situ hybridization) records showed a clonal result in 84 patients and of these 65/84 (77%) had an aberration of chromosome 14. These comprised 48/65 with inv(14), 6/65 t(14;14), 2/65 t(X;14), 1/65 TCL1 gene rearrangement by FISH and 8/65 with TRA/TRD involvement by FISH. Other frequent abnormalities seen were i(8)(q10) in 31/84 (39%) and complex karyotypic abnormality in 40/84 (48%). Lower frequency abnormalities seen were monosomy 11 in 8/84 (9%), monosomy 12 in 8/84 (9%), trisomy 8 in 6/84 (7%), 17p loss in 5/84 (6%) and mononsomy 13 in 4/84 (5%). Alemtuzumab was used in 116 patients, 69/116 (59%) receiving it as frontline treatment and 47/116 (41%) as salvage therapy. In 50/116 (43%) alemtuzumab was used as single agent, the remaining 66/116 (57%) receiving combination therapy, mostly pentostatin. Mean time from diagnosis to receiving alemtuzumab was 6.8 months (range 0-53 months). Overall response rate (ORR) to alemtuzumab was 94/116 (81%) with complete remission (CR) 69/116 (59%), partial remission (PR) 25/116 (22%) and no response (NR) 20/116 (17%). Alemtuzumab produced better response rates when used as frontline therapy. Table 2 summarizes these results and OS and DFI are shown in figures B and C. Allogeneic stem cell transplant (allo-SCT) was performed in 34 patients. Median OS post allo-SCT was 22 months and median DFI 31 months. Relapse rate post allo-SCT was 47%, non-relapse mortality 38% and transplant related mortality 29%. Figures D and E show OS and DFI post allo-SCT. Although relapse rates are high post allo-SCT there is a small cohort of patients who are achieving long term remission. We analysed OS by decade of diagnosis covering 3 decades 1990-1999, 2000-2009 and 2010-2019. The median OS for the whole cohort was 20.6 months with median OS of 21 months, 23 months and 19 months for each decade respectively. Results are shown in figure A. There was no statistically significant difference between the curves by log-rank analysis. DISCUSSION: Immunophenotyping results were similar to previous published data on T-PLL except for an increase in CD25 expression at 50%. Our data shows that outcomes in T-PLL have remained unchanged since the first decade of alemtuzumab usage, with no improvement in OS in the last 20 years. Despite improvements in diagnostic techniques and supportive care median OS is static at approximately 20 months. These results highlight the need for novel therapies in T-PLL. Given the rarity of T-PLL, international, multi-center, randomised trials are needed to improve outcomes. Disclosures Cross: Royal Marsden Cancer Charity: Other: MD Residency, Research Funding. Iyengar:Abbvie: Honoraria; Janssen: Honoraria. Dearden:Janssen: Honoraria; Genentech: Honoraria; Abbvie: Honoraria; Sanofi: Honoraria.

Introduction Since interim results from the EuroNet-PHL-C1 study1were published in 2013 showing that the gonadotoxic drug procarbazine in COPP can be safely replaced with dacarbazine (COPDac) it is increasingly common practice to modify escalated BEACOPP (eBPP) by removing oral procarbazine and replacing it with intravenous dacarbazine (250mg/m2 D2-3), hoping to reduce haematopoietic stem cell and gonadal toxicity. However, published data of 'escalated BEACOPDac (eBPDac)' regimen are very limited. Methods We collected retrospective data from 15 centres in the UK, Ireland and France, that offer eBPDac therapy for first line advanced stage Hodgkin Lymphoma, and compared outcomes with matched patients treated with eBPP at 4 UK centres. Most patients were treated as per HD15 or HD18 protocol. The 24 patients treated in Paris followed the AHL2011 protocol with two courses of eBPDac given upfront and if iPET2 negative were deescalated to 4 cycles of ABVD. Results From 2009, 141 patients were managed first line with either eBPP (n=52) or eBPDac (n=89) with median follow-up 40 months for eBPP and 12.7 months for eBPDac patients. Patients were well matched with no significant differences in age (median: 28), sex, stage (stage 3/4: 82%) and international prognostic score (IPS3+:65%). More patients treated with eBPDac received only 4 cycles of treatment (43% vs 12%; p Toxicity was compared over the first 4 cycles. There was no difference in day 8 ALT between the two regimens although the mean day 8 neutrophil count was lower in eBPDac than eBPP patients (1.84 vs 2.35; p=0.043; G-CSF given day 9). There was a trend to fewer non-elective days of in-patient care for eBPDac compared with eBPP (mean: 2.78 vs 6.00; p=0.0846), and eBPDac patients received fewer red cell transfusions during cycles 1 to 4 compared with eBPP patients (Mean 1.87 units vs 4.33 units; p 6 months post chemotherapy follow-up had a similar rate of return of menstrual cycles (eBPP: 20/21; eBPDac: 13/16), although eBPDac patients appeared to restart menstruation earlier post chemotherapy completion (mean: 3.85 months vs 8.65 months, p=0.0018). However, this could also reflect the higher mean chemotherapy cycle number completed by the eBPP women (5.86 vs 4.67; p Conclusions Accepting the limitations of a retrospective study, we suggest that substituting dacarbazine for procarbazine is unlikely to compromise the efficacy of eBPP in frontline therapy of patients with advanced Hodgkin Lymphoma and may have some toxicity benefits. As it is highly unlikely that this single drug substitution will ever be tested in a prospective trial, publishing real-world data from eBPDac patients is important. References 1. EuroNet-PHL-C1 study interim report published 14/08/2013 http://www.anzchog.org/docs/public-resources/euronet-recommendation.pdf?sfvrsn=0 2. Borchmann P et al. 2018;390:2790-2802 Disclosures Brice: BMS: Honoraria; Takeda France: Consultancy, Honoraria; Millennium Takeda: Research Funding. Menne:Pfizer: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel grant; Jazz: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel grant, Research Funding, Speakers Bureau; Janssen: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Kite/Gilead: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel grant, Research Funding, Speakers Bureau; Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel grant, Research Funding, Speakers Bureau; Kyowa Kirin: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel grant, Research Funding, Speakers Bureau; Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Daiichi Sankyo: Honoraria, Membership on an entity's Board of Directors or advisory committees; Astra Zeneca: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Bayer: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel grant, Research Funding, Speakers Bureau; Amgen: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel grant, Research Funding, Speakers Bureau; Roche: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Takeda: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau. Osborne:Novartis: Other: Travel; Pfizer: Honoraria, Speakers Bureau; Servier: Consultancy; MSD: Consultancy; Takeda: Consultancy, Honoraria, Other: Travel, Speakers Bureau; Gilead: Consultancy; Roche: Consultancy, Honoraria, Other: Travel, Speakers Bureau. Ardeshna:Gilead: Consultancy, Honoraria; Celgene: Consultancy, Honoraria. Collins:Gilead: Consultancy, Honoraria. Cwynarski:Adienne: Consultancy; Takeda: Consultancy, Other: conference and travel support , Speakers Bureau; Gilead: Consultancy, Other: conference and travel support, Speakers Bureau; Celgene: Consultancy; Roche,: Consultancy, Other: conference and travel support, Speakers Bureau; Autolus: Consultancy; KITE: Consultancy; Atara: Consultancy; Janssen: Other: conference and travel support, Speakers Bureau. Iyengar:Takeda: Honoraria; Janssen: Honoraria; Gilead: Honoraria; Abbvie: Honoraria; Roche: Honoraria. Martinez-Calle:ABBVIE: Other: Travel support. McKay:Epizyme: Consultancy, Honoraria. Nagumantry:Takeda: Honoraria, Speakers Bureau; Alexion: Speakers Bureau; Abbvie: Honoraria. Shah:Abbvie: Consultancy. Uttenthal:Roche: Honoraria; Takeda: Honoraria; Jazz: Honoraria. McMillan:BMS: Honoraria; F. Hoffmann-La Roche Ltd: Honoraria, Speakers Bureau; Sandoz: Honoraria; Celgene: Honoraria, Speakers Bureau; Novartis: Honoraria; Gilead: Honoraria; MSD: Honoraria; Pfizer: Honoraria, Research Funding. Follows:Roche: Consultancy, Honoraria, Speakers Bureau; AZ: Consultancy, Honoraria, Speakers Bureau; Janssen: Consultancy, Honoraria, Speakers Bureau; Abbvie: Consultancy, Honoraria, Speakers Bureau.

Introduction: Predicting the risk of histologic transformation (HT) from indolent follicular lymphoma (FL) to a more aggressive form of lymphoma represents a major challenge in managing patients with FL. We assessed the incidence of HT in the GALLIUM study (NCT01332968) and determined risk factors for transformation and impact on clinical outcomes. Methods: In the Phase III GALLIUM study, patients with previously untreated FL were randomized to receive either the anti-CD20 antibody rituximab (R; 375mg/m² on Day (D) 1 of each cycle) or obinutuzumab (G; 1000mg on D1, 8, and 15 of Cycle 1 and D1 of subsequent cycles) in combination with chemotherapy (CHOP, CVP or bendamustine). Patients who achieved at least a partial response at the end of induction therapy proceeded to maintenance therapy with the same antibody, every 2 months for 2 years, or until progression of disease. Repeat biopsies at progression were not mandatory but carried out in case of clinical suspicion of HT. The rate of HT, as assessed by the local pathologist, in patients with a repeat biopsy at the time of disease progression/relapse was an exploratory endpoint. Results: 1202 patients were enrolled. After a median follow up of 57.3 months, 315 (26.2%) patients progressed (median time to relapse, 25.3 months); of these 315 patients, 46 (14.6%) had a biopsy at first progression due to a clinical suspicion of transformation. Forty patients, corresponding to 3.3% of all patients enrolled in GALLIUM and 12.7% of those that progressed, had biopsy-confirmed HT. Among 153 patients with disease progression within 24 months (POD24), 31/153 (20.3%) had HT. Fewer patients transformed in the G-chemo arm (16/40; 40%) compared with R-chemo (24/40; 60%). In total, 116 patients relapsed in the G-chemo arm versus 159 in the R-chemo arm. Compared with no HT, patients with HT were more likely to be male and have bone marrow involvement, stage 3A FL, high FL International Prognostic Index risk, low hemoglobin (Hb), elevated serum lactate dehydrogenase (LDH), elevated beta-2-microglobulin, and high total metabolic tumor volume (Table). A comparison of chemotherapy backbones showed a trend towards higher HT incidence with bendamustine (5.8% [26/686]) compared with CVP, 4.3% (5/117) and CHOP, 2.3% (9/399). A multivariate cause-specific cox model identified several risk factors for HT, including elevated LDH levels (hazard ratio [HR], 4.27 [95% CI: 2.08─8.78]; p Conclusions: In GALLIUM, a low rate of HT was observed over 5 years, with the majority occurring within the first 2 years. Patients with POD12 had poor OS regardless of whether transformation occurred or not. Risk factors for HT included elevated LDH, anemia, and male gender. Patients with HT, especially those with progression of disease within 24 months, had poor OS compared to patients who relapsed with persistent FL. Disclosures Casulo: Celgene: Research Funding; Gilead: Honoraria, Other: Travel, accommodation, expenses; Roche: Other: Travel, accommodation, expenses. Herold:Roche: Membership on an entity's Board of Directors or advisory committees, Research Funding; GILEAD: Membership on an entity's Board of Directors or advisory committees; Celgene: Membership on an entity's Board of Directors or advisory committees; Janssen: Membership on an entity's Board of Directors or advisory committees. Hiddemann:Celgene: Consultancy, Honoraria; Janssen: Consultancy, Honoraria, Research Funding; Roche: Consultancy, Honoraria, Research Funding; Gilead: Consultancy, Honoraria; Bayer: Research Funding; Vector Therapeutics: Consultancy, Honoraria. Iyengar:Roche: Honoraria; Abbvie: Honoraria; Gilead: Honoraria; Janssen: Honoraria; Takeda: Honoraria. Marcus:Roche / Genentech: Honoraria, Speakers Bureau; Gilead: Consultancy. Seymour:AbbVie: Consultancy, Honoraria, Research Funding, Speakers Bureau; Takeda: Consultancy; Acerta: Consultancy; Roche: Consultancy, Research Funding, Speakers Bureau; Celgene: Consultancy, Research Funding, Speakers Bureau; Janssen: Consultancy, Research Funding. Launonen:F. Hoffmann-La Roche Ltd: Employment. Knapp:F. Hoffmann-La Roche Ltd: Employment. Nielsen:F. Hoffmann-La Roche Ltd: Employment, Equity Ownership. Mir:Roche: Other: Previous employment.

Phosphoinositide-3 kinase (PI3K) pathway activation contributes to mantle cell lymphoma (MCL) pathogenesis, but early-phase studies of the PI3K p110δ inhibitor GS-1101 have reported inferior responses in MCL compared with other non-Hodgkin lymphomas. Because the relative importance of the class IA PI3K isoforms p110α, p110β, and p110δ in MCL is not clear, we studied expression of these isoforms and assessed their contribution to PI3K signaling in this disease. We found that although p110δ was highly expressed in MCL, p110α showed wide variation and expression increased significantly with relapse. Loss of phosphatase and tensin homolog expression was found in 16% (22/138) of cases, whereas PIK3CA and PIK3R1 mutations were absent. Although p110δ inhibition was sufficient to block B-cell receptor-mediated PI3K activation, combined p110α and p110δ inhibition was necessary to abolish constitutive PI3K activation. In addition, GDC-0941, a predominantly p110α/δ inhibitor, was significantly more active compared with GS-1101 against MCL cell lines and primary samples. We found that a high PIK3CA/PIK3CD ratio identified a subset of primary MCLs resistant to GS-1101 and this ratio increased significantly with relapse. These findings support the use of dual p110α/p110δ inhibitors in MCL and suggest a role for p110α in disease progression.

Introduction: Primary mediastinal B Cell Lymphoma (PMBL) is a high-grade non-hodgkin lymphoma with distinct clinical and biological features. Optimal chemotherapy for this lymphoma is not established but some centres favour more intensive regimes such as DA EPOCH-R over R-CHOP. The role of consolidation radiotherapy is yet to be clarified and whether it can be omitted in those patients with a negative end-of-treatment PET scan (EOT PET) regardless of induction chemotherapy. Furthermore, the occurrence of false positive EOT PET scans may lead to overtreatment. The aim of this study was to establish the outcomes of patients (pts) with PMBL who had been treated in a single centre. Methods: Pts diagnosed with PMBL between 2003 and 2015 in Royal Marsden Hospital were included. Data was collected from electronic patient records and PET CT images review. Survival was defined from date of diagnosis until date of death or date of last follow up. Results: Thirty-four pts were identified with characteristics as shown in the table. Median diameter of the mediastinal mass was 12cm (range 5.5 - 24cm); 25 (74%) pts had a mass of ≥ 10cm. The majority of pts received R-CHOP chemotherapy (2 had 14 day cycles, 30 had 21 day cycles), 1 R-GCVP and another R-PACEBOM. Median number of cycles of chemotherapy was 6 (range 1-8). Seven out of 32 (22%) pts received involved field radiotherapy (IFRT). EOT PET was available for 30 pts. Median time to obtaining EOT PET from completion of chemotherapy was 31 days (20-81). Twenty-three out of 30 pts had EOT PET negative disease with a Deauville score (DS) of 1-3. Twenty-one of these 23 pts did not receive IFRT. Two of these 21 pts relapsed in the mediastinum and were treated with salvage chemotherapy followed by autologous stem cell transplant (ASCT) of whom 1 died due to their lymphoma. The 2 patients who received consolidation radiotherapy remain in remission. Seven out of 30 pts had a positive EOT PET (DS 4-5); of whom 5 received IFRT. Two out of 5 patients relapsed and proceeded with further chemotherapy of whom 1 died due to treatment-related causes while the other 4 patients were alive at time of last follow-up. Two pts with a positive EOT PET did not have IFRT, 1 proceeded with salvage chemotherapy but died due to lymphoma and the other patient was followed up with serial PET scans and ultimately the residual avidity was considered to be due to thymic hyperplasia. Conclusion: Our analysis demonstrates that for the 23 patients who achieved a complete metabolic response on EOT PET the risk of relapse was low (9%) (despite that only 2 patients received consolidation radiotherapy) and only one patient (4%) died of lymphoma. Thus the majority of patients with a negative EOT PET scan following R-CHOP chemotherapy may not need consolidation radiotherapy. This finding should be taken into account when considering the risk/benefit of adding radiotherapy treatment to patients who are already in metabolic CR after chemotherapy. Consolidation radiotherapy is currently being investigated in a prospective IELSG37 trial, NCT01599559. Table. Table. Disclosures Chau: Eli-Lilly: Honoraria, Other: Advisory Board, Research Funding; Bristol Meyers Squibb: Other: Advisory Board; MSD: Other: Advisory Board; Bayer: Other: Advisory Board; Roche: Other: Advisory Board; Merck Serono: Other: Advisory Board, Research Funding; Five Prime Therapeutics: Other: Advisory Board; Astra-Zeneca: Other: Advisory Board; Janssen-Cilag: Research Funding; Sanofi Oncology: Research Funding. Cunningham:Roche pharmaceuticals: Research Funding.

Abstract 1652 Background: Activation of the phosphoinositide-3 kinase (PI3K) pathway contributes to mantle cell lymphoma (MCL) pathogenesis, but early phase studies of the p110δ selective inhibitor GS-1101 demonstrate inferior responses in MCL compared to CLL and indolent NHL. The relative importance of the class Ia PI3K isoforms - p110α, p110β and p110δ in MCL is not clear. While p110δ is enriched in leucocytes, p110α gene amplification has been reported in 68% of MCL. Loss of PTEN expression occurs in approximately 15% of MCL and evidence in solid tumors suggests an essential role for p110β in PI3K signaling associated with PTEN loss. We previously reported significant up-regulation of p110α expression in relapsed disease as well as significantly greater in vitro cytotoxicity with GDC0941, a predominantly p110α/δ inhibitor, compared to the p110δ selective inhibitor GS-1101 in MCL. To investigate this further, we used isoform selective inhibitors to study the relative contribution of class Ia isoforms to PI3K signaling in the context of B-cell receptor (BCR) activation, p110α over-expression and PTEN deletion in this disease. We also screened tumor cells for activating mutations in PIK3CA and PIK3R1, the genes encoding p110α and p85α respectively. Methods: Peripheral blood mononuclear cells (PBMCs) and lymph nodes from MCL patients were used in addition to two MCL cell lines Jeko1 and Granta519. Goat anti-human IgM f(a'b) fragments were used for BCR stimulation. Immunohistochemistry (IHC) and western blotting were used to assess PTEN expression. In addition to GDC0941 and GS-1101, A66 was used for p110α-selective inhibition and TGX-221 for p110β inhibition. GS-1101 was purchased from Active Biochem and all other inhibitors from Selleck Chem. Changes in downstream targets of PI3K (p-Akt t308, p-Akt s473 and p-S6 s235/236) were evaluated using western blotting. DNA was extracted from 10 primary samples and 2 cell lines. Exons 9, 10, 11, 13, 15 and 16 of PIK3R1 and exons 9 and 20 of PIK3CA, were sequenced and screened for activating mutations. Results: p110δ is expressed at high levels in MCL and p110δ selective inhibition with GS-1101 was sufficient to block BCR-stimulated activation of the PI3K pathway in MCL cells. In order to investigate the relevance of increased p110α in relapsed MCL, that we previously reported, we treated the Granta519 MCL cell line, which exhibits p110α gene amplification and constitutive Akt phosphorylation, with GS-1101 and GDC0941. In GS-1101 treated cells, phosphorylation of Akt was still detectable at low levels after 2 hours of treatment while p-Akt was undetectable in cells treated with equimolar concentrations (1μM) of GDC0941. At 24 hours, GS-1101 treated cells showed an increase in Akt phosphorylation compared to 2 hour levels suggesting ongoing p110α mediated signaling despite p110δ inhibition, whereas p-Akt remained undetectable in GDC-0941 treated cells. These changes were reflected in downstream phosphorylation of ribosomal S6. The addition of the highly selective p110β inhibitor TGX221 to GS-1101 did not have any additional effect on p-Akt whereas adding a p110α selective inhibitor (A66) mimicked the activity of GDC0941, further supporting the role of p110α in p110δ-independent PI3K signaling. We found loss of PTEN expression in 17% (25/147) of MCL biopsies by IHC. There was no change in the pattern of class Ia isoform expression in tumors with loss of PTEN and adding a p110β inhibitor to GS-1101 did not increase cytotoxicity in MCL primaries that had loss of PTEN expression. No activating PIK3CA or PIK3R1 mutations were detected in 10 primary MCL samples and 2 cell lines. Conclusion: In healthy B-cells, p110δ is essential for BCR mediated PI3K signaling but both p110α and p110δ contribute to tonic PI3K signaling. Our studies confirm a similar essential role for p110δ in MCL cells both by its expression and its role in BCR signaling. However, over-expression of p110α in MCL, especially in relapsed disease, increases the contribution of this isoform to tonic PI3K signaling thereby limiting the efficacy of p110δ-selective inhibition. The increased expression of p110α with relapse may reflect reduced dependence of tumor cells on survival signals from their microenvironment. We conclude that whereas PI3K p110β does not appear to play a significant role in MCL, inhibition of both p110α and δ isoforms appears essential for effective PI3K inhibition in this disease. Disclosures: Auer: Pharmacyclics: Research Funding. Gribben:Celgene: Honoraria; Roche: Honoraria; Pharmacyclics: Honoraria; GSK: Honoraria; Mundipharma: Honoraria; Gilead: Honoraria.

Abstract 1565 Background: The relatively low incidence of MCL (0.55 per 100,000) poses a challenge for effective evaluation of novel therapies in patients affected by this aggressive and incurable lymphoma. A xenograft model of human MCL provides a useful model for pre-clinical evaluation of novel drugs, rational drug combinations and biomarkers. The only mouse xenograft model of primary human MCL reported was established by injecting CD19 selected PBMCs in a subcutaneously implanted human embryonic bone graft in SCID mice and SCID mice without subcutaneous bone grafts did not show engraftment. NOD/SCID/IL2Rγ chain null (NSG) mice, which lack mature T or B cells and are also deficient in NK cells, permit engraftment of a wider range of primary human cells compared to SCID mice. In view of recent reports of successful engraftment of human CLL in NSG mice, we hypothesised that primary human MCL can be established in these mice. Methods: We initially introduced luciferase transduced Jeko-1 cells at 2 concentrations – 0.5 and 2 million cells by tail vein injection of 8 to 12 week old γ-irradiated (3.75 Gy) NSG mice in an attempt to track the kinetics and distribution of MCL cells. Bioluminescent imaging (BLI) following injection of luciferin was performed weekly for 4 weeks. We then injected NSG mice (4 replicates) with 107, T-cell depleted, previously cyropreserved human MCL cells from 3 patients. Mice were bled at 3, 6 and 12 weeks and flow cytometry was performed on PBMCs for human CD45, CD5 and CD20. Mice were sacrificed at 20 weeks and immunohistochemistry (IHC) for human CD20 and cyclin D1 was performed on formalin fixed paraffin embedded spleen, ileo-caecal junction and liver while FACS for human CD45, CD5 and CD20 was performed on bone marrow cells flushed from the femur. Tissues harbouring CD20 and cyclin D1 positive cells were stained with Ki-67 to assess proliferation and FISH for t(11;14) was performed on fresh cells isolated from the spleen to further confirm engraftment. Results: NSG mice injected with Jeko-1 cells showed rapid engraftment at both concentrations (0.5 and 2 million) on assessment with BLI, with a more rapid progression after 3 weeks in mice injected with 2 million cells. Mice had to be sacrificed at 4 weeks because of illness. Bioluminescence was seen primarily in the bone marrow, spleen and along the spine. Consistent engraftment was also seen in all mice injected with sample 1 - PBMCs from a patient in 1st relapse with blastoid morphology, classic immunophenotypic features and the IgH:CCND1 translocation. CD5 and CD20 double positive cells were consistently detected at 6 and 12 weeks in the peripheral blood of all 4 mice examined. Mice were not visibly ill at 20 weeks but had gross splenomegaly at sacrifice. No lymph node or abdominal masses were found. A clear human CD5/CD20 population was found on flow cytometry of bone marrow cells. The splenic architecture was disrupted in mice that engrafted, compared to those that did not and a heavy infiltration of CD20 and cyclin D1 positive cells was found with proliferation estimated at 35–40% by Ki-67 staining. Interphase FISH on fresh cells derived from the spleen showed the IGH/CCND1 [t(11;14)] rearrangement in all cells examined. Scattered CD20 positive cells were observed in the liver but no polyps or submucosal infiltration was found in the ileo-caecal regions of these mice. NSG mice injected with samples 2 and 3 had no evidence of engraftment in peripheral blood, bone marrow or other tissues. Conclusion: Our studies demonstrate that a mouse model of human MCL can be established in NSG mice and are encouraging for developing this model for pre-clinical evaluation of novel drugs. The lymphoma cells that engrafted were from a patient with relapsed, blastoid MCL suggesting that a more aggressive phenotype may favor engraftment as seen with AML xenografts in NSG mice. Ongoing studies are examining additional patient samples and the need for T cell depletion. This model will also provide an opportunity to investigate the role of tumor-initiating side populations in this disease. Disclosures: Gribben: Celgene: Honoraria; Roche: Honoraria; Pharmacyclics: Honoraria; GSK: Honoraria; Mundipharma: Honoraria; Gilead: Honoraria.

Abstract 1654 Background: Mantle cell lymphoma (MCL) is an incurable, aggressive subtype of non-Hodgkin lymphoma in which there is a need for novel targeted therapies. Activation of the PI3K-Akt pathway and its role in the pathogenesis of MCL has been highlighted in a number of studies. Constitutive activation of the PI3K pathway inactivates GSK-3β, a downstream target of Akt, that can phosphorylate cyclin D1 resulting in its nuclear export. There is also evidence that cyclin D1 mRNA stability and translation is enhanced by this pathway. The class Ia PI3K p110 catalytic subunit isoforms α, β and δ are primarily implicated in oncogenesis. While the PI3K p110δ isoform is known to be enriched in lymphocytes, a gain of PIK3CA (the gene encoding PI3K p110α) copy number has been shown to be a frequent alteration in MCL. The expression and relative importance of the individual Class Ia PI3K isoforms has not been documented in this disease. With the development of isoform selective inhibitors, this is an important issue that needs to be addressed. Aims: We studied the expression of class Ia PI3K isoforms in primary MCL with relation to morphological variants and disease status. We also compared the efficacy of PI3K inhibition in MCL cell lines and primary samples using two novel inhibitors, GDC-0941(predominantly p110α/δ-selective) and CAL-101 (δ-selective), both of which are in early phase clinical trials. Methods: Tissue microarrays were constructed from triplicate 1mm cores from 144 MCL biopsies and 16 tonsil controls. The levels of p110α, p110β and p110δ isoforms were then determined by immunohistochemistry using isoform-specific antibodies. The in vitro effect of PI3K inhibitors on cell viability and apoptosis was studied in 4 MCL cell lines, (Jeko-1, Granta519, REC-1 and JVM-2), and 15 primary MCL samples. Expression of the class Ia PI3K isoforms and changes in downstream targets of PI3K were determined by western blotting. Results: P110δ was expressed at a consistently higher level in MCL samples and normal tonsil controls compared to the α and β isoforms, while p110β expression was weak and significantly lower than p110α expression. On comparing expression of isoforms at diagnosis and relapse, p110α expression was significantly increased beyond 1st relapse compared to diagnostic biopsies (p=0.04) and tonsil controls (p=0.02), an observation that was even more apparent in 6 paired samples [p=0.008, median IHC score 19.6 (5.0−53.2) at diagnosis vs. 91.5 (38.6 − 129) beyond 1st relapse]. No significant change was found in the expression of p110β or p110δ between diagnostic and relapse samples. There was no significant difference in expression levels of the 3 isoforms between blastoid and non-blastoid morphological variants. Expression of both the p110α and δ isoforms was detected by western blotting in 4 MCL cell lines, but only Jeko-1 cells were sensitive to inhibition with GDC-0941. CAL-101 produced little or no apoptosis in all 4 cell lines. In primary MCL samples, GDC-0941 was consistently more potent than CAL-101, with decrease in cell viability of 32 vs. 20% at 1μM (p=0.15), 51 vs. 25% at 5μM (p=0.02) and 67 vs. 35% at 10μM (p Conclusion: Our studies demonstrate that although p110δ is the most consistently expressed isoform, the expression of the p110α subunit increases significantly in multiply relapsed MCL. This observation, in combination with significantly greater in vitro sensitivity of MCL primary samples to GDC-0941, compared to the p110δ-selective inhibitor CAL-101, provides strong evidence for further evaluation of GDC-0941 in this disease. Disclosures: Gribben: Roche: Honoraria; Celgene: Honoraria; GSK: Honoraria; Mundipharma: Honoraria; Gilead: Honoraria; Pharmacyclics: Honoraria. Joel:Astra Zeneca: Research Funding; Intellikine: Research Funding.