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Purpose: TP53 aberration (TP53 mutation and/or 17p deletion) is the most important predictive marker in chronic lymphocytic leukemia (CLL). Although each TP53 aberration is considered an equal prognosticator, the prognostic value of carrying isolated (single-hit) or multiple (multi-hit) TP53 aberrations remains unclear, particularly in the context of targeted agents. Patients and Methods: We performed deep sequencing of TP53 using baseline samples collected from 51 TP53 aberrant patients treated with ibrutinib in a phase II study (NCT01500733). Results: We identified TP53 mutations in 43 patients (84%) and del(17p) in 47 (92%); 9 and 42 patients carried single-hit and multi-hit TP53, respectively. The multi-hit TP53 subgroup was enriched with younger patients who had prior treatments and unmutated immunoglobulin heavy-chain variable region gene status. We observed significantly shorter overall survival, progression-free survival (PFS), and time-to-progression (TTP) in patients with multi-hit TP53 compared with those with single-hit TP53. Clinical outcomes were similar in patient subgroups stratified by 2 or >2 TP53 aberrations. In multivariable analyses, multi-hit TP53 CLL was independently associated with inferior PFS and TTP. In sensitivity analyses, excluding mutations below 1% VAF demonstrated similar outcome. Results were validated in an independent population-based cohort of 112 patients with CLL treated with ibrutinib. Conclusions: In this study, single-hit TP53 defines a distinct subgroup of patients with an excellent long-term response to single-agent ibrutinib, whereas multi-hit TP53 is independently associated with shorter PFS. These results warrant further investigations on prognostication and management of multi-hit TP53 CLL. See related commentary by Bomben et al., p. 4462

Ibrutinib has now been approved for treatment of chronic lymphocytic leukemia (CLL) in both front-line setting and as later-line treatment. However, knowledge about the outcomes and adverse events (AE) among patients at a population-based level is still limited. Objectives: To report outcomes and AEs in a population-based cohort treated with ibrutinib outside clinical trials. Methods: We conducted a multicenter, retrospective cohort study including all patients with CLL treated with ibrutinib. Results: In total, 205 patients were included of whom 39 (19%) were treatment-naïve. The median follow-up was 21.4 months (interquartile range (IQR), 11.9,32.8), the estimated overall survival at 12 months was 88.8% (95% confidence interval (CI); 84.3%, 93.3%), and the estimated progression-free survival at 12 months was 86.3% (95% CI; 81.3%, 91.2%). During follow-up, 200 (97.6%) patients had at least one AE and 100 (48.8%) patients had at least one grade ≥3 AE. Eighty-six patients (42.0%) discontinued ibrutinib, hereof 47 (54.7%) due to AEs and 19 (22.1%) had progression of CLL or Richter transformation. Conclusions: In our study, we find comparable, though slightly inferior, overall, and progression-free survival, and discontinuation due to toxicity was higher compared with clinical trials. Patient training and information may improve treatment adherence outside clinical trials.

Introduction Ibrutinib is an oral irreversible inhibitor of Bruton's tyrosine kinase for treatment of chronic lymphocytic leukemia (CLL). Ibrutinib has demonstrated superior efficacy for patients with TP53 aberration or relapsed/refractory (R/R) CLL; and more recently superior progression free survival (PFS) has been demonstrated compared to chemoimmunotherapy as first line therapy. However, knowledge about the outcomes and adverse events (AE) upon ibrutinib among patients at a population-based level are still limited. The aim of the here presented study is to explore outcomes of ibrutinib treatment in a population-based cohort of patients with CLL treated with ibrutinib in Denmark. Methods In this retrospective study, patients from 8 hospitals in Denmark, who were diagnosed with CLL and treated with ibrutinib from April 2014 until February 2019 were included. Medical records were retrospectively reviewed to obtain information. Patients receiving ibrutinib within clinical trials were excluded. Overall survival (OS) was defined as time from ibrutinib start to death from any cause while PFS was defined as time from ibrutinib start to progression or death from any cause. PFS and OS were analyzed with the Kaplan-Meier method while cumulative incidence was calculated with the Aalen-Johansen estimator. Results In total, 205 patients with CLL receiving ibrutinib treatment were identified from hospital records and registries. The median follow-up was 21.4 months (IQR, 11.9-32.8) and the median time on ibrutinib was 16.8 months (IQR, 6.0-28.1). The median age at treatment initiation was 72.8 years (IQR, 65.7-77.8), 128 (62.4%) were male, and 111 (63.4%) were Binet stage B/C at treatment initiation out of 175 with available information regarding clinical stage. Thirty-nine (19.0%) received ibrutinib as first-line, and 166 for R/R CLL with a median of 2 (range, 1-8) prior treatment regimens. Information on TP53 aberration was available for 149 and regarding IGHV mutation for 147 patients, 111 (74.5%) had TP53 aberration and 107 (72.8%) were IGHV unmutated. Eighty-six patients (42.0%) discontinued ibrutinib during follow-up with a median time until discontinuation of 9.3 months (IQR, 3.0-23.2). Forty-seven (54.7%) discontinued due to AEs, 19 (22.1%) due to progression (12 had progression of CLL and 7 had Richter's transformation) while the remaining 20 (23.2%) discontinued due to other reasons. The estimated cumulative incidence of discontinuation at 12 months was 24.8% (95% CI: 18.6-30.9). The estimated OS after 12 and 24 months was 88.8% (95%CI: 84.3-93.3) and 76.8% (95%CI: 70.4-83.2) and the estimated PFS after 12 and 24 months was 87.3% (95%CI: 82.5-92.1) and 72.4% (95%CI: 65.5-79.2). One hundred and eighty-eight (91.7%) experienced at least one AE, among these 45 (23.9%) experienced a grade 3+. The most common AEs were hemorrhage (tendency to bruise, epistaxis etc.) which occurred in 86 (42.0%) of all and musculoskeletal and connective tissue disorders (arthralgia, myalgia etc.) which occurred in 82 (40.0%). Thirty-one (15.1%) patients experienced atrial fibrillation while on ibrutinib and 14 (6.8%) developed hypertension. One hundred and thirty-seven patients (66.8%) had at least one infection and among these 80 (58.4%) were hospitalized with an infection. The most common infections were lower respiratory tract infections and urinary tract infections that occurred for 88 (42.9%) and 41 (20.0%). The estimated cumulative incidence for any infection was 58.9% (95%CI: 52.0-65.9) at 12 months. Conclusion This is the first study describing outcomes for a population-based cohort of CLL patients treated with ibrutinib in Denmark. Real-world studies are warranted, to confirm the results from clinical trials. In this study, patients appear to have comparable OS and types of AE compared with the RESONATE trial. Differences in frequency of AEs compared to the clinical trial may reflect the focus of clinicians in routine practice. Discontinuation in this cohort was higher compared to clinical trials but comparable to previously reported real-world studies. While ibrutinib can be safely managed in routine clinical practice, this study demonstrates that a quarter of patients discontinue treatment due to mainly AEs. Further patient training and information, and in some instances personalized treatment with other targeted agents based on adverse event profile, may improve treatment adherence. Disclosures Aarup: Research Committee, Rigshospitalet: Research Funding. Enggaard:Abbie: Other: Advisory board; Gilead: Other: Advisory board; Janssen: Other: Advisory board. Frederiksen:Gilead: Research Funding; Abbvie: Research Funding; Janssen Pharmaceuticals: Research Funding; Novartis: Research Funding; Alexion: Research Funding. Niemann:Novo Nordisk Foundation: Research Funding; AstraZeneca: Consultancy, Other: Travel Grant, Research Funding; Sunesis: Consultancy; Acerta: Consultancy; CSL Behring: Consultancy; Roche: Other: Travel Grant; Janssen: Consultancy, Other: Travel Grant, Research Funding; Gilead: Other: Travel Grant; Abbvie: Consultancy, Other: Travel Grant, Research Funding.