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Background: Aromatase inhibitors (AIs) are highly effective at reducing recurrences and mortality in postmenopausal patients with estrogen receptor positive breast cancer (ER+ BC). Poor anti-proliferative (Ki67) response or ER+ BCs to AIs after 2 weeks is associated with worse long-term outcomes. Factors that relate to the degree of the response may identify markers and/or mechansims of resistance. Methods: The PeriOperative Endocrine Therapy for Individualizing Care (POETIC) trial randomized 4,480 with ER+ BC to 2 weeks’ AI before surgery or no presurgical treatment. All patients within the bottom 15% of Ki67 responders to AI (poor responders [PRs]; n=177 with RNA extracted) were selected from and matched to good responders (GRs) within the 50% showing the best response (n=190). Matching was based on baseline Ki67 levels as measured by immunohistochemistry (IHC). Response to AI was measured by the percentage change in Ki67 after 2 weeks’ treatment. PRs were further divided into groups expressing high ESR1 (PRs ESR1HIGH; n=119) and low ESR1 (PRs ESR1LOW; n=58) levels since there were very few GRs with low ESR1. RNAseq, targeted exome DNA sequencing of 87 BC/resistance related genes and measurement of plasma estradiol levels by mass spectrometry were performed to understand mechanisms of de novo resistance. Intrinsic subtypes were estimated from RNAseq data. Results: More than 90% of PRs ESR1LOW were non-luminal subtypes with low expression of estrogen-responsive genes. In contrast, 11% of PRs ESR1HIGH were non-luminal compared to 4% of GRs but only HER2-enriched subtypes were significantly higher in PR ESR1HIGH (p=0.05, Fisher exact). While AI treatment had limited impact on Ki67 IHC values in PRs ESR1HIGH, PGR expression was more than 2-fold lower after 2 weeks of AI. Gene-set enrichment analysis showed significantly lower expression of estrogen-response genes in PRs ESR1HIGH compared to GRs (FDR< 10-9) at baseline despite similar percentage of Luminal subtypes in PRs ESR1HIGH and GRs. Plasma estradiol levels were correlated with expression of estrogen-response genes (FDR=0.01) and levels were significantly lower in PRs ESR1HIGH compared to GRs (p=0.003, Mann Whitney). PRs ESR1HIGH had significantly more mutations in RB1, TP53, ARID1B and DNAH11 genes (p< 0.05, Fisher exact). TP53 mutations were significantly enriched in Luminal-A PRs ESR1HIGH compared to GRs (22% and 3% respectively; p=0.003, Fisher exact), but not in Luminal-B tumors (23% and 15% mutated respectively). Discussion and conclusions: In approximately 33% of PRs, de novo AI resistance was associated with and most likely due to low expression of ER/ESR1 and estrogen-responsive genes in non-luminal tumors. In the remaining tumors, AI treatment still impacted some estrogen responsive genes but had limited downstream impact on suppressing proliferation. This might be due to mutations including in TP53 that limit suppression of proliferation downstream of estrogen signaling. The proportion of Luminal tumors in GRs and PRs ESR1HIGH was similar, suggesting better outcome of Luminal-A tumors on AI is likely due to their better intrinsic prognosis rather than better response to endocrine therapy. Citation Format: Eugene F. Schuster, Elena López-Knowles, Anastasia Alataki, Lila Zabaglo, Elizabeth Folkerd, David Evans, Kally Sidhu, Holly Tovey, Perry Maxwell, Nicholas Turner, Stephen Johnston, Manuel Salto-Tellez, Maggie Chon U Cheang, John Robertson, Ian Smith, Judith Bliss, Mitch Dowsett. PD10-07 Low plasma estradiol, low expression of estrogen responsive genes and TP53 mutations are associated with poor anti-proliferative response to aromatase inhibitors [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr PD10-07.

Background: Aromatase inhibitors (AIs) are one of the main treatment strategies for the clinical management of estrogen receptor-positive (ER+) breast cancer (BC). Despite prolonged time to recurrence and initial clinical responses, >20% of patients eventually relapse, and previous studies have shown an association of poor anti-proliferative response to AIs and worse outcome. High immune activity in ER+ tumors may be associated with worse outcome, in contrast to ER-negative BC where immune infiltration is a feature associated with better outcome. Our work focused on understanding the correlations between immune cell infiltration and response to AI. Methods: All patients with ER+ HER2- tumors within the bottom 15% of Ki67 anti-proliferative responders to AIs (poor responders [PRs]; n=177) were selected from the PeriOperative Endocrine Therapy for Individualizing Care (POETIC) trial and matched on baseline Ki67 levels to good responders (GRs) within the 50% showing the best response (n=190). Response to AI was measured by the Ki67 percentage change after 2 weeks of treatment. PRs were further divided into groups expressing high ESR1 (PRs ESR1HIGH; n=119) and low ESR1 (PRs ESR1LOW; n=58) levels to represent PR subgroups that showed partial or no response to AIs. The percentage of stromal tumor-infiltrating lymphocytes (TILs) was assessed. Multiple immunofluorescence was performed for ER, CD3, CD20, CD68, FOXP3, and CD3/FOXP3 in 15 baseline samples from each of the GR, PR ESR1HIGH, and PR ESR1LOW populations and immune cell density in stromal or tumor compartments was estimated. Spearman correlations of TILs with Consensus tumor microenvironment (TME) deconvolution and Molecular Signatures Database hallmark gene sets were conducted. The relationship between the immune markers’ density and genes, hallmark gene sets and Consensus TME was assessed. Results: The percentage of TILs was significantly higher in the PR ESR1HIGH and PR ESR1LOW compared to the GRs (adjusted p< 0.05). As expected, TILs were highly correlated with T cells (particularly T-regulatory cells) and immune hallmark gene sets. There was a tendency for higher density of each of the immune markers in PRs compared to GRs, with significant differences being observed in stromal B-cell marker CD20 density (p< 0.05). Analysis showed a significant correlation between TILs and stromal FOXP3 marker density (FDR< 0.05), and stromal biomarker density was highly correlated to the gene expression of the encoding genes of the same tumors (CD3/CD3D, FOXP3/FOXP3, and CD20/MS4A1) (FDRs< 0.05). There was also a strong and significant correlation between the stromal expression of CD20, CD3, FOXP3, and CD3/FOXP3 with the immune hallmark gene sets (FDRs< 0.05). Finally, the immune phenotyping showed the expected correlations with TME deconvolution, with particularly strong correlations of CD20 and CD3 with B- and T-cell gene signatures, respectively (FDRs< 0.05). Conclusions: Different immune features indicated a broad involvement of several immune cell types in PRs to AIs, suggesting that the immune system might be associated with resistance of ER+ breast tumors to AI treatment. Spatial gene expression profiling is ongoing to characterize these tumors further and investigate potential mechanisms of AI resistance. Citation Format: Anastasia Alataki, Gene Schuster, Lila Zabaglo, Perry Maxwell, Elena López-Knowles, Elizabeth Folkerd, David Evans, Kally Sidhu, Holly Tovey, Nicholas Turner, Stephen Johnston, Maggie Chon U Cheang, John Robertson, Manuel Salto-Tellez, Ian Smith, Judith Bliss, Mitch Dowsett. PD10-08 Immune cell infiltration associated with poor anti-proliferative response to aromatase inhibitors in postmenopausal women with primary ER-positive HER2-negative breast cancer [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr PD10-08.

Preclinical data suggest that combined gamma-tocotrienol with pentoxifylline ameliorates radiotherapy-induced gastrointestinal damage.To test whether gastrointestinal symptoms arising after radiotherapy, and persisting after maximal medical therapy, can be improved using Tocovid SupraBio 200 mg and pentoxifylline 400 mg orally twice daily for one year. Patients stratified by severity of symptoms, and randomised to active treatment or matched placebo were assessed after 12 months. The primary end point was improvement in gastrointestinal symptoms measured using the Inflammatory Bowel Disease Questionnaire, bowel subset score. Changes in bio-markers of fibrosis were assessed.62 patients, median age 66, 34(55%) treated for prostate, 21(34%) gynaecological, 6(10%) anal and one(1%) rectal cancer were recruited; 40(65%) randomised to treatment, 22(35%) to placebo, 39 months (median) after radiotherapy completion. Gamma tocotrienol was not detected in serum in 41% of treated patients, despite good compliance with study medication. Treatment was completed in 28(70%) and 17(77%) patients in the treatment and placebo groups respectively. No improvement in symptom scores nor in quality of life was identified. Thirteen serious adverse events occurred. A transient ischaemic attack, was possibly related to pentoxifylline, others were assessed as unlikely to be related to treatment. Levels of EGF, PDGF and FGF were significantly reduced and consistent trends in reduced inflammation were seen during treatment but were not sustained once treatment ended.This single centre study closed prematurely and therefore data interpretation is of necessity limited. No clinical benefit was demonstrated. However, biochemical data suggest that this intervention does have anti-inflammatory and anti-fibrotic effects.

Background The presence or absence of residual disease following neoadjuvant systemic anti-cancer therapy (neoSACT) for HER2-positive early breast cancer (HER2+ EBC) provides powerful prognostic information that may guide subsequent adjuvant treatment for the individual patient. Pathological complete response (pCR) following neoSACT identifies a population with excellent outcomes in whom the balance of toxicity associated with the current treatment pathway may be disproportionate to the absolute clinical benefit. Aims HER2-RADiCAL seeks to reduce the burden of toxicity and healthcare costs of treating HER2+ EBC by testing the hypothesis that pCR can be used as a functional response biomarker to select patients who can safely receive less intensive therapy, including avoiding anthracyclines, with minimal or no loss of efficacy in the population. Trial design and eligibility criteria HER2-RADiCAL is a response-directed interventional cohort (single-arm) study embedded within a real-world data driven clinical pathway model. Participants will be registered within 6 weeks of completion of breast cancer surgery. The main eligibility criteria include clinical stage T1N1 or T2N0-1 at diagnosis and locally-determined pCR (ypT0/Tis ypN0) after standard of care taxane-based (non-anthracycline) neoadjuvant chemotherapy, trastuzumab and pertuzumab. After registration participants will continue to receive trastuzumab to complete a total of 9 cycles including those (neo-)adjuvant cycles administered prior to study entry. Participants will receive no further pertuzumab nor any adjuvant chemotherapy. Statistical methods The primary clinical endpoint is relapse free interval. Recruitment of 720 participants over 3 years will provide 90% power to exclude an event rate >6.5% at 3 years. Secondary endpoints include relapse-free survival, invasive breast cancer-free survival, invasive disease-free survival, distant recurrence-free interval, breast cancer-free interval, treatment pathway adherence and cost-effectiveness. Real-world data driven clinical pathway model Health economic modelling will compare the protocol-driven study cohort with two comparator pathways: a non-response adapted maximum therapy pathway (the standard clinical pathway prior to the study) and a real-world representative pathway taken from 4-nation UK National Health Service data at the beginning and end of the study. Patient and public involvement Patient advocates have shaped the research by confirming that the main outcomes being evaluated are important to patients and that the interventional cohort design, with power to exclude an absolute risk of recurrence outwith a 2-3% margin of historical control data, is acceptable and preferable to a randomised controlled trial, which would take longer to get answers and need many more patients to be included. They have been involved in protocol design, including methodology, sample collection and patient follow-up, and their input has shaped the patient information materials and consent forms. Patient advocates will have an ongoing key role in overseeing the progress of the study as members of the Trial Management Group, and they will also have an important role in communicating the study results to patients and the public. Current status HER2-RADiCAL is planned to open at ~40 UK sites commencing in September 2021. Citation Format: Iain Macpherson, Stuart McIntosh, Lucy Kilburn, Holly Tovey, Sarah Kernaghan, Katie Goddard, Indrani Bhattacharya, Clinton Boyd, Charlotte Coles, Cliona Kirwan, Mairead Mackenzie, Ciara O’Brien, Alistair Ring, Claire Snowdon, Hilary Stobart, Duncan Wheatley, Andrew Wardley, Abeer Shaaban, Peter Hall, David Cameron, Judith Bliss. The HER2-RADiCAL study (Response ADaptive CAre pLan) - Tailoring treatment for HER2 positive early breast cancer [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr OT2-05-01.

Purpose:Aromatase inhibitor (AI) treatment is the standard of care for postmenopausal women with primary estrogen receptor–positive breast cancer. The impact of duration of neoadjuvant endocrine therapy (NET) on molecular characteristics is still unknown. We evaluated and compared changes of gene expression profiles under short-term (2-week) versus longer-term neoadjuvant AIs.Experimental Design:Global gene expression profiles from the PeriOperative Endocrine Therapy for Individualised Care (POETIC) trial (137 received 2 weeks of AIs and 47 received no treatment) and targeted gene expression from 80 patients with breast cancer treated with NET for more than 1 month (NeoAI) were assessed. Intrinsic subtyping, module scores covering different cancer pathways and immune-related genes were calculated for pretreated and posttreated tumors.Results:The differences in intrinsic subtypes after NET were comparable between the two cohorts, with most Luminal B (90.0% in the POETIC trial and 76.3% in NeoAI) and 50.0% of HER2 enriched at baseline reclassified as Luminal A or normal-like after NET. Downregulation of proliferative-related pathways was observed after 2 weeks of AIs. However, more changes in genes from cancer-signaling pathways such as MAPK and PI3K/AKT/mTOR and immune response/immune-checkpoint components that were associated with AI-resistant tumors and differential outcome were observed in the NeoAI study.Conclusions:Tumor transcriptional profiles undergo bigger changes in response to longer NET. Changes in HER2-enriched and Luminal B subtypes are similar between the two cohorts, thus AI-sensitive intrinsic subtype tumors associated with good survival might be identified after 2 weeks of AI. The changes of immune-checkpoint component expression in early AI resistance and its impact on survival outcome warrants careful investigation in clinical trials.

Supplementary Data from Impact of Duration of Neoadjuvant Aromatase Inhibitors on Molecular Expression Profiles in Estrogen Receptor–positive Breast Cancers

Supplementary Figure from Impact of Duration of Neoadjuvant Aromatase Inhibitors on Molecular Expression Profiles in Estrogen Receptor–positive Breast Cancers

Background We investigated the first-line activity of vinflunine in patients with penis cancer. Cisplatin-based combinations are commonly used, but survival is not prolonged; many patients are unfit for such treatment or experience toxicity that outweighs clinical benefit. Methods Twenty-five patients with inoperable squamous carcinoma of the penis were recruited to a single-arm, Fleming–A’Hern exact phase II trial. Treatment comprised 4 cycles of vinflunine 320 mg/m2, given every 21 days. Primary endpoint was clinical benefit rate (CBR: objective responses plus stable disease) assessed after 4 cycles. Seven or more objective responses or disease stabilisations observed in 22 evaluable participants would exclude a CBR of 40% being probable. Results Twenty-two participants were evaluable. Ten objective responses or disease stabilisations were confirmed. CBR was 45.5%, meeting the primary endpoint; partial response rate was 27.3%. Seven patients received >4 cycles of vinflunine. Dose reduction or treatment delay was required for 20% of cycles. In all, 68% of patients experienced at least one grade 3 adverse event. Two deaths on treatment were not caused by disease progression. Conclusions Pre-specified clinical activity threshold was exceeded. Toxicity was in keeping with experience in other tumours. Vinflunine merits further study in this disease. Trial registration NCT02057913.

Background Radium-223 is a bone-seeking, alpha-emitting radionuclide used in metastatic castration-resistant prostate cancer (mCRPC). Radium-223 increases the risk of fracture when used in combination with abiraterone and prednisolone. The risk of fracture in men receiving radium-223 monotherapy is unclear. Patients and Methods This was a prospective, multicenter phase II study of radium-223 in 36 men with mCRPC and a reference cohort (n = 36) matched for fracture risk and not treated with radium-223. Bone fractures were assessed using whole-body magnetic resonance imaging. The primary outcome was risk of new fractures. Results Thirty-six patients were treated with up to six 4-week cycles of radium-223. With a median follow-up of 16.3 months, 74 new fractures were identified in 20 patients. Freedom from fracture was 56% (95% confidence interval, 35.3-71.6) at 12 months. On multivariate analysis, prior corticosteroid use was associated with risk of fracture. In the reference cohort (n = 36), 16 new fractures were identified in 12 patients over a median follow-up of 24 months. Across both cohorts, 67% of all fractures occurred at uninvolved bone. Conclusions Men with mCRPC, and particularly those treated with radium-223, are at risk of fracture. They should receive a bone health agent to reduce the risk of fragility fractures., Micro-Abstract Radium-223 increases the risk of fracture in combination with abiraterone and prednisolone. The fracture risk of radium-223 monotherapy is unclear. This prospective study assessed fracture incidence in men treated with radium-223 matched with a cohort that did not have radium-223. We identified 74 new fractures in 20 patients receiving radium-223. Most fractures occurred in bones without apparent metastases. Bone health agents should be mandatory before starting radium-223.

AIMS Ki67 is a well-established immunohistochemical marker associated with cell proliferation that has prognostic and predictive value in breast cancer. Quantitative evaluation of Ki67 is traditionally performed by assessing stained tissue slides with light microscopy. Automated image analysis systems have become available and, if validated, could provide greater standardisation and improved precision of Ki67 scoring. Here, we aimed to evaluate the use of the Cognition Master Professional Suite (CogM) image analysis software, which is a simple system for scoring Ki67 in primary breast cancer samples. METHODS AND RESULTS Sections from 94 core-cut biopsies, 20 excision specimens and 29 pairs of core-cut biopsies and excision specimens were stained for Ki67 with MIB1 antibody and the Dako EnVision FLEX Detection System. Stained slides were scanned to convert them to digital data. Computer-based Ki67 scoring was performed with CogM. Manual Ki67 scoring assessment was conducted on previously stained sections from the same biopsies with a clinically validated system that had been calibrated against the risk of recurrence. A high correlation between manual and digital scores was observed [rCores = 0.92, 95% confidence interval (CI) 0.87-0.94, P

Background: Prognosis in older patients with breast cancer (BC) is worse compared to younger patients. No robust and specific tool to predict the risk of recurrence (TTR) for women aged 70 and over is likely due to the lack of representation of this group in the data from clinical trials. In the POETIC trial, of estrogen receptor-positive (ER+) and mainly human epidermal growth factor receptor 2 negative (HER2-) BC (88%), peri-operative aromatase inhibitor (POAI) did not improve treatment outcome, but patients with low baseline Ki67 value (Ki67B) or low POAI-induced Ki67 value (Ki67_2wk) had good outcome with standard of care therapy (usually adjuvant endocrine therapy (adjET) with the addition of chemotherapy as clinically indicated). In this study, we sought to develop a multi-parametric algorithm, named Ki67Cal, by integrating Ki67_2wk value with tumour characteristics to predict TTR for patients > 70 years old (yr) with early ER+HER2- BC treated with adjET only. Methods: Within POETIC, 39% (n=1744) of the randomised patients (n = 4480) were >70 years old. There were 813 patients aged > 70yr, with ER+HER2- BC, randomised to POAI treatment and treated with adjET only. A power calculation indicated that 811 such patients were sufficient to develop a prediction model that minimized overfitting, allowed up to 8 predictors, for predicting 5-years TTR with a median follow-up of 5.24 years and an overall event rate per 1000 person-years = 0.027, and provided an anticipated performance in terms of model fit R2 = 0.08 (Riley et al. BMJ 2020). A three-fold cross-validation approach was applied; an optimal list of features was selected in the training set (n = 538, events = 70); the agreement between expected and observed outcomes from the algorithm on the validation set (n = 275, events = 37) was evaluated by calibration plot. Multivariable Ridge Cox Regression model of significant parameters was built on the dataset merging training and validation datasets (n = 813) for precise estimates of the coefficients of parameters. A subset of post-POAI samples (n = 99) was gene expression profiled with Nanostring to allow pseudo-Oncotype, pseudo-EndoPredict, and RUO-Prosigna scores calculated (Buus et al. npj Breast cancer 2021). The risk groups classified by the Ki67Cal and gene-expression assays (GEP) were compared. Results: Within this cohort, the 5-year TTR was 34.5% (C.I. 24.9-47.9) for those with a high Ki67_2wk (>=10%) and 12.3% (C.I. 9.1-16.7) in those with a high Ki67B that was suppressed to Ki672wk < 10%. The significant features were Ki67_2wk, sampling type (core vs. excision) at surgery, and pathological variables (tumour size, grade, and nodal status) for the final Ki67Cal algorithm. Stratifying patients into five groups (quintiles) by Ki67Cal identified 60% of patients with TTR of < 5% at 5yrs, and 20% of patients with TTR of > 30% at 5yrs. As an exploratory analysis, the risk groups by Ki67Cal and GEP were compared (Table 1). To date, these assays are optimized to be used on untreated ER+HER2- samples; there were fairly good agreements between the high-risk group defined by Ki67Cal with pseudo-EndoPredict and RUO-Prosigna respectively, and low-risk groups by Ki67Cal with Prosigna probably because Prosigna scores are driven by proliferation score. Conclusion: The relatively poor outcome of patients >70yrs in POETIC emphasizes the need for prognostic tools that identify patients who may be treated with endocrine therapy alone or conversely should be considered for additional therapy. Ki67Cal provides a simple tool that identified very low-risk and high-risk patients in 80% of patients with ER+HER2- BC. Table 1: Comparison of the risk groups defined by Ki67Cal algorithm with the three commonly used gene-expression assays (pseudo-EndoPredict, pseudo-Oncotype and RUO-Prosigna) applied on the post-peri-operative aromatase inhibitor samples. Citation Format: Maggie Chon U Cheang, Monisha Dewan, Lucy Kilburn, Gabriele Morani, Lila Zabaglo, Kally Sidhu, Holly Tovey, Xixuan Zhu, Chris Holcombe, Anthony Skene, Ian Smith, John Robertson, Alistair Ring, Nicholas Turner, Judith Bliss, Mitch Dowsett. Multi-parametric algorithm integrating on-treatment Ki67 value and standard clinicopathological variables to predict risk of recurrences for women > 70 years old with early ER+HER2- tumours in POETIC trial [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P2-03-07.

Background: POETIC was a phase III clinical trial, with patients randomised 2:1 to 2-week perioperative aromatase inhibitor (POAI) vs control for postmenopausal women with oestrogen receptor positive (ER+) early breast cancer (BC) (Smith et al., Lancet Oncology 2020). Our previous study on POETIC trial patients with ER+ human epidermal growth factor receptor 2 positive (HER2+) BC suggested both HER2 enriched subtype (HER2-E) and immune enrichment pre-POAI (baseline, B) are main drivers of poor early response to POAI (Bergamino et al., 2022). However, some patients with HER2-E or immune enriched BC at B still showed good response to POAI. In this study, we aim to further investigate a sub-cohort of ER+ HER2+ BC from the POETIC trial, including a subset of aforementioned HER2-E tumours, to further explore the multi-modal molecular characteristics of the tumours resistant to POAI. Methods: Proliferation rate was assessed as percentage of cancer cells stained by Ki67. Patient POAI response was determined by Ki67 reduction at 2 weeks of treatment. A sub-cohort of 37 patients were selected based on response and classified as poor responders (PR, reduction < 30%, n=18), good responders (GR, reduction > 90%, n=11) and good responders with HER2-E BC at B (GR, reduction > 65%, n=8). Paired B and post-POAI (surgery, S) samples were taken from each patient of the sub-cohort. Multiplex immunofluorescence (mIF) was performed on these samples, measuring the immune cell densities in stroma and tumour compartments using five biomarkers: CD3 (all T cells), CD20 (B cells), CD68 (Macrophages), FOXP3 (regulatory T cells), and CD3 FOXP3 co-expression. The samples were also profiled using Breast Cancer 360TM (NanoString, BC360), covering the expressions of 758 genes and 46 biological signatures. Wilcoxon test, hierarchical clustering and spearman correlation test were performed to compare the tumour characteristics of GR and PR. Results: In this study, two B and four S samples were not achievable for mIF experiments due to low tumour content. At B (n = 35), among the five mIF biomarker measurements in stroma and tumour, only the stromal CD3 density was significantly different between GR (median = 0.0013) and PR (median = 0.0003, p = 0.041). In GR, HER2-E BC at B were separated into immune-high and immune-low groups with mIF biomarkers at B; the immune-high group was more likely to change into luminal subtypes post-POAI, while the immune-low group remained HER2-E. After POAI, the density changes in five mIF biomarkers in stroma and CD68 in tumour were all significantly higher in PR than GR (Table 1, n of paired samples = 62). The BC360 signatures of BC p53 (p < 0.001), BC proliferation (p < 0.001), LumB (p < 0.001) and HER2-E correlation coefficients (p < 0.001) were significantly downregulated in GR after POAI, while LumA correlation coefficients (p < 0.001) were notably increased. Conclusions: Our results suggest that for this sub-cohort, increased stromal immune response is associated with poor response to 2-week POAI in ER+ HER2+ early BC. HER2-E GR display visible immune heterogeneity at B. Lower-risk BC characteristics were exhibited in GR after the 2-week treatment. Further integrating mIF imaging data and additional digital spatial profiling are ongoing to reveal additional characteristics of ER+ HER2+ BC and tumour microenvironment predicting POAI resistance. Table 1: List of medians of log2 fold changes in mIF biomarker densities between GR and PR among the 62 paired samples, and Wilcoxon test p-values. Citation Format: Xixuan Zhu, Hui Xiao, Elena López-Knowles, Milana A. Bergamino Sirvén, Anastasia Alataki, Perry Maxwell, Holly Tovey, Lucy Kilburn, Chris Holcombe, Anthony Skene, Ian Smith, John Robertson, Katherine A Hoadley, Roberto Salgado, Judith Bliss, Nicholas Turner, Manuel Salto-Tellez, Gene Schuster, Mitch Dowsett, Maggie Chon U Cheang. Deconstructing the molecular characteristics of ER+ HER2+ early breast cancer in the POETIC trial using multiplex immunofluorescence and gene expression profiles [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P2-03-08.

Background In the TNT trial of triple negative breast cancer (NCT00532727), germline BRCA1/2 mutations were present in 28% of carboplatin responders. We assessed quantitative measures of structural chromosomal instability (CIN) to identify a wider patient subgroup within TNT with preferential benefit from carboplatin over docetaxel. Patients and methods Copy number aberrations (CNAs) were established from 135 formalin-fixed paraffin-embedded primary carcinomas using Illumina OmniExpress SNP-arrays. Seven published [allelic imbalanced CNA (AiCNA); allelic balanced CNA (AbCNA); copy number neutral loss of heterozygosity (CnLOH); number of telomeric allelic imbalances (NtAI); BRCA1-like status; percentage of genome altered (PGA); homologous recombination deficiency (HRD) scores] and two novel [Shannon diversity index (SI); high-level amplifications (HLAMP)] CIN-measurements were derived. HLAMP was defined based on the presence of at least one of the top 5% amplified cytobands located on 1q, 8q and 10p. Continuous CIN-measurements were divided into tertiles. All nine CIN-measurements were used to analyse objective response rate (ORR) and progression-free survival (PFS). Results Patients with tumours without HLAMP had a numerically higher ORR and significantly longer PFS in the carboplatin (C) than in the docetaxel (D) arm [56% (C) versus 29% (D), PHLAMP,quiet = 0.085; PFS 6.1 months (C) versus 4.1 months (D), Pinteraction/HLAMP = 0.047]. In the carboplatin arm, patients with tumours showing intermediate telomeric NtAI and AiCNA had higher ORR [54% (C) versus 20% (D), PNtAI,intermediate = 0.03; 62% (C) versus 33% (D), PAiCNA,intermediate = 0.076]. Patients with high AiCNA and PGA had shorter PFS in the carboplatin arm [3.4 months (high) versus 5.7 months (low/intermediate); and 3.8 months (high) versus 5.6 months (low/intermediate), respectively; Pinteraction/AiCNA = 0.027, Padj.interaction/AiCNA = 0.125 and Pinteraction/PGA = 0.053, Padj.interaction/PGA = 0.176], whilst no difference was observed in the docetaxel arm. Conclusions Patients with tumours lacking HLAMP and demonstrating intermediate CIN-measurements formed a subgroup benefitting from carboplatin relative to docetaxel treatment within the TNT trial. This suggests a complex and paradoxical relationship between the extent of genomic instability in primary tumours and treatment response in the metastatic setting., Highlights • Patients with intermediate levels of allelic imbalanced CNAs show a better response rate to carboplatin in TNT. • The lack of amplifications on 1q, 8q and 10p is associated with a superior carboplatin response in TNT. • The relation between chromosomal instability in primary tumours and carboplatin response in advanced settings is non-linear.

Background: oestrogen receptor positive/ human epidermal growth factor receptor positive (ER+/HER2+) breast cancers (BCs) are less responsive to endocrine therapy than ER+/HER2- tumours. Mechanisms underpinning the differential behaviour of ER+HER2+ tumours are poorly characterised. Our aim was to identify biomarkers of response to 2 weeks’ presurgical AI treatment in ER+/HER2+ BCs. Methods: all available ER+/HER2+ BC baseline tumours (n=342) in the POETIC trial were gene expression profiled using BC360™ (NanoString) covering intrinsic subtypes and 46 key biological signatures. Early response to AI was assessed by changes in Ki67 expression and residual Ki67 at 2 weeks (Ki67 2wk). Time-To-Recurrence (TTR) was estimated using Kaplan-Meier methods and Cox models adjusted for standard clinicopathological variables. New molecular subgroups (MS) were identified using consensus clustering. Findings: HER2-enriched (HER2-E) subtype BCs (44.7% of the total) showed poorer Ki67 response and higher Ki67 2wk (p2wk. Five new MS that were associated with differential response to AI were identified. HER2-E had significantly poorer TTR compared to Luminal BCs (HR 2.55, 95% CI 1.14–5.69; p=0.0222). The new MS were independent predictors of TTR, adding significant value beyond intrinsic subtypes. Interpretation: our results show HER2-E as a standardised biomarker associated with poor response to AI and worse outcome in ER+/HER2+. HRD, TP53 mutational score and immune-tumour tolerance are predictive biomarkers for poor response to AI. Lastly, novel MS identify additional non-HER2-E tumours not responding to AI with an increased risk of relapse. Funding: Cancer Research UK (CRUK/07/015).

Background The TNT trial (NCT00532727) showed no evidence of carboplatin (C) superiority over docetaxel (D) overall in metastatic triple negative breast cancers (TNBC), but a C benefit was observed in the pre-specified sub-group analysis in patients with a gBRCA1/2 mutation (Tutt et al, Nat Med 2018). Given only ~30% of patients have a gBRCA1/2 mutation, broader predictive biomarkers of response are needed. In this cohort we previously found that DNA Damage Response (DDR) signatures were associated with improved C response in chemotherapy (CT) naïve patients only (Tovey et al, ASCO 2020). Since DDR activities influence tumour immune-microenvironment, we explored the predictive ability of immune cell markers and performed integrative analyses on multi-omics features to identify novel TNBC subgroups. Patients and Methods Tumour infiltrating lymphocytes (TILs) were evaluated on haematoxylin and eosin stained primary tumour (PT) slides for 222/376 TNT patients. Formalin-fixed paraffin-embedded PT tissues from 186/376 TNT patients were successfully profiled using total RNA-sequencing. Matched recurrence (REC) was also sequenced for 13 patients. Twenty-five immune signatures were assessed. Logistic regression and restricted mean progression free survival (PFS) were applied to delineate the relationship of these features with treatment outcomes. Random forest clustering of multi-omics DDR and immune biology markers, including gene expression signatures and mutation/methylation status, was applied to identify subgroups. We further molecularly characterised these clusters through supervised clustering of 693 gene expression “modules” (sets of co-expressed genes), immune cell deconvolution and genomic scars. Results Immune gene expression signatures and TILs were highly correlated. Average immune infiltration based on ConsensusTME was lower in mutated/methylated tumours compared with BRCA1 wildtype tumours (p=0.04). Immune signature score markers decreased from PT to REC, demonstrating a dynamic immune microenvironment. In the overall population and when restricting to prior CT treated patients, high immune infiltration (gene expression based & TILs) was associated with response to D while C response rates were not associated with immune scores (interaction p-values< 0.05). This did not translate to a PFS benefit. Multi-omics clustering identified 6 biological subgroups including immune enriched, immune depleted, DDR deficient and proficient clusters as well as 2 small clusters with no obvious distinguishing features. Immune enriched TNBC were predominantly basal-like immune activated with high B-cell/T-cell diversity. Immune depleted TNBC showed higher activity of proliferation and DDR pathway modules. DDR proficient tumours had low expression of immune markers and enrichment for ESR1/PGR expression, markers of extra cellular formation, cell structure, lipid metabolism and proliferation. The DDR deficient cluster was enriched for proliferation and demonstrated high number of TILs despite no apparent enrichment for gene expression-based immune modules. In the prior CT treated cohort, the immune enriched cluster had preferential response to D (62.5% (D) vs. 29.4% (C); p=0.02). The immune depleted cluster had preferential response to C (8.0% (D) vs. 40.0% (C); p=0.01). Numbers were too small to assess differential response within the other clusters or in the CT naïve cohort. Conclusions Tumours with high immune features have high response to D while those with low immune features have preferential response to C in advanced TNBC. Combining multi-omics markers of DDR deficiency and immune biology can identify clusters of patients with distinct biological profiles and differential treatment specific response rates. Citation Format: Holly Tovey, Orsolya Sipos, Katherine A Hoadley, Joel S Parker, Jelmar Quist, Sarah Kernaghan, Lucy Kilburn, Roberto Salgado, Sherene Loi, Richard D Kennedy, Ioannis Roxanis, Patrycja Gazinska, Sarah E. Pinder, Judith Bliss, Charles M. Perou, Syed Haider, Andrew Tutt, Anita Grigoriadis, Maggie Chon U Cheang. Histopathological and molecular immune landscape and DNA damage response signatures to predict response to carboplatin and docetaxel in TNT trial TNBC cohort [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr PD9-06.

Background Activation of the PI3K/AKT/mTOR pathway through loss of phosphatase and tensin homolog (PTEN) occurs in approximately 50% of patients with metastatic castration-resistant prostate cancer (mCRPC). Recent evidence suggests that combined inhibition of the androgen receptor (AR) and AKT may be beneficial in mCRPC with PTEN loss. Patients and methods mCRPC patients who previously failed abiraterone and/or enzalutamide, received escalating doses of AZD5363 (capivasertib) starting at 320 mg twice daily (b.i.d.) given 4 days on and 3 days off, in combination with enzalutamide 160 mg daily. The co-primary endpoints were safety/tolerability and determining the maximum tolerated dose and recommended phase II dose; pharmacokinetics, antitumour activity, and exploratory biomarker analysis were also evaluated. Results Sixteen patients were enrolled, 15 received study treatment and 13 were assessable for dose-limiting toxicities (DLTs). Patients were treated at 320, 400, and 480 mg b.i.d. dose levels of capivasertib. The recommended phase II dose identified for capivasertib was 400 mg b.i.d. with 1/6 patients experiencing a DLT (maculopapular rash) at this level. The most common grade ≥3 adverse events were hyperglycemia (26.7%) and rash (20%). Concomitant administration of enzalutamide significantly decreased plasma exposure of capivasertib, though this did not appear to impact pharmacodynamics. Three patients met the criteria for response (defined as prostate-specific antigen decline ≥50%, circulating tumour cell conversion, and/or radiological response). Responses were seen in patients with PTEN loss or activating mutations in AKT, low or absent AR-V7 expression, as well as those with an increase in phosphorylated extracellular signal-regulated kinase (pERK) in post-exposure samples. Conclusions The combination of capivasertib and enzalutamide is tolerable and has antitumour activity, with all responding patients harbouring aberrations in the PI3K/AKT/mTOR pathway. Clinical Trial Number NCT02525068, Highlights • Preclinical data suggest that inhibition of both the AR and PI3K/AKT/mTOR signalling has synergistic activity in PTEN loss prostate cancer models. • Here we present a phase I clinical trial of enzalutamide combined with the AKT inhibitor capivasertib in patients with mCRPC and show that this regimen is safe and tolerable. • This combination has antitumour activity with all responding patients harbouring aberrations in the PI3K/AKT/mTOR pathway.

Background A distinctive trait of triple negative breast cancer (TNBC) is the acquisition of genome wide highly aberrant copy number states, which is more evident in metastatic settings. The level of copy number alterations can be characterized by quantitative estimates of chromosomal instability, such as allelic imbalanced copy number aberrations, telomeric allelic imbalance (NtAI), homologous recombination deficiency (HRD) score, referred here as genomic scars. Several of these scars are reported as being indicative of BRCAness and potential predictive and/or prognostic biomarkers of chemotherapy response, currently mostly demonstrated in neoadjuvant settings in TNBC. Aims Using several genomic scar measures, we aim to capture chromosomal instability and test their predictive and prognostic value in metastatic or recurrent locally advanced triple negative or BRCA1/2 mutated breast cancer in the TNT trial. Methods Patients recruited to TNT (n=376) had ER-/PR-/Her2- breast cancer or were germline BRCA mutation carriers. Genome-wide copy numbers (CN) were derived from FFPE samples including primary tumours and positive lymph nodes (n=183, docetaxel=93, carboplatin=90; BRCA1 mut=25). Genomic scars were generated using ASCAT (Van loo et al., PNAS 2010) CN profiles. HRD scores were established by Myriad Genetics, Inc. assay (n=272). BRCA1-like classifier was applied as described in Schouten et al., Mol Onc 2015. Shannon diversity index was calculated using ASCAT raw CN profiles. Association of genomic scars with PAM50 subtypes and BRCA1 deficiency status were evaluated using Kruskal-Wallis test; p-values were adjusted for multiple comparisons (Dunn's test). Statistical significance was defined as p Results HRD and NtAI scores were higher in basal like samples compared to non-basal like (median diff. HRD=11.5, p=0.005; NtAI=3, p=0.04). HRD (p=2e-14) and NtAI (p=0.003) scores were also higher in BRCA1 deficient (BRCA1 germline/somatic mutant or BRCA1 methylated) samples compared to non-deficient. Using the BRCA1-like classifier, 42 out of 50 BRCA1 deficient samples and 93 out of 133 BRCA1 non-deficient/undetermined samples were identified as BRCA1-like. The Shannon diversity index, measuring CN heterogeneity, clustered samples into 3 groups. Analysis of ORR showed non-significant trends to preferential response rates with docetaxel in cluster 1 and 3. Membership of cluster 2 predicted higher ORR to carboplatin over docetaxel (interaction p=0.017). PFS indicated a treatment effect in cluster 2, but not in cluster 1 or 3; there was no evidence of interaction between subgroups and treatment (p=0.15). Conclusions Our results suggest that the overall heterogeneity of the copy number landscape is a promising area for seeking predictive/prognostic biomarkers in metastatic TNBC, and combined with other modalities of high-dimensional omics data could provide essential treatment response information. Citation Format: Sipos O, Tovey H, Quist J, Haider S, Nowinski S, Gazinska P, Kernaghan S, Toms C, Timms KM, Lanchbury JS, Linn SC, Pinder SE, Bliss JM, Tutt A, Cheang MC, Grigoriadis A, On behalf of the TNT Trial Management Group and Investigators. Characterization of chromosomal instability in the TNT trial: A randomized phase III trial of carboplatin compared with docetaxel for patients with metastatic or recurrent locally advanced triple negative or BRCA1/2 breast cancer (CRUK/07/012) [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P1-06-07.

Importance Patients with breast cancer remain at risk of relapse after adjuvant therapy. Celecoxib has shown antitumor effects in preclinical models of human breast cancer, but clinical evidence is lacking. Objective To evaluate the role of celecoxib as an addition to conventional therapy for women with ERBB2 (formerly HER2)–negative primary breast cancer. Design, Setting, and Participants The Randomized European Celecoxib Trial (REACT) was a phase 3, randomized, double-blind study conducted in 160 centers across the UK and Germany testing 2 years of adjuvant celecoxib vs placebo among 2639 patients recruited between January 19, 2007, and November 1, 2012, with follow-up 10 years after treatment completion. Eligible patients had completely resected breast cancer with local and systemic therapy according to local practice. Patients with ERBB2-positive or node-negative and T1, grade 1 tumors were not eligible. Randomization was in a 2:1 ratio between celecoxib or placebo. Statistical analysis was performed from May 5, 2019, to March 5, 2020. Interventions Patients received celecoxib, 400 mg, or placebo once daily for 2 years. Main Outcomes and Measures The primary end point was disease-free survival (DFS), analyzed in the intention-to-treat population using Cox proportional hazards regression and log-rank analysis. Follow-up is complete. Results A total of 2639 patients (median age, 55.2 years [range, 26.8-86.0 years]) were recruited; 1763 received celecoxib, and 876 received placebo. Most patients’ tumors (1930 [73%]) were estrogen receptor positive or progesterone receptor positive and ERBB2 negative. A total of 1265 patients (48%) had node-positive disease, and 1111 (42%) had grade 3 tumors. At a median follow-up of 74.3 months (interquartile range, 61.4-93.6 years), DFS events had been reported for 487 patients (19%): 18% for those who received celecoxib (n = 323; 5-year DFS rate = 84%) vs 19% for those who received placebo (n = 164; 5-year DFS rate = 83%); the unadjusted hazard ratio was 0.97 (95% CI, 0.80-1.17; log-rankP = .75). Rates of toxic effects were low across both treatment groups, with no evidence of a difference. Conclusions and Relevance In this randomized clinical trial, patients showed no evidence of a DFS benefit for 2 years’ treatment with celecoxib compared with placebo as adjuvant treatment of ERBB2-negative breast cancer. Longer-term treatment or use of a higher dose of celecoxib may lead to a DFS benefit, but further studies would be required to test this possibility. Trial Registration ClinicalTrials.gov Identifier:NCT02429427and isrctn.org Identifier:ISRCTN48254013

1074 Background: In the Triple Negative Trial we observed no improved response rate (RR) to C over D in aTNBC [Tutt et al, Nat Med 2018], but we did in BRCA1/2 mutated (mut) patients (pts). We hypothesise tumors with other aberrant DNA damage response (DDR) characteristics having higher RR to DNA damage inducing C than D. Methods: We tested the predictive value of DDR process related gene expression signatures (PARPi7, chromosomal instability CIN70, TP53 & DDR Deficiency (DDRD)) on 192 treatment naïve primary tumours (PT) by total RNA-sequencing. Odds ratio (OR) for RR are reported. Paired PT & recurrent (REC) signature scores were compared. Results: Unexpectedly, high DDRD and PARPi7 were associated with higher RR to D than C ( p =0.01 & 0.06). No effect was observed for CIN70 or TP53 signature. To assess whether the unexpected results were due to biological changes 12 PT-REC pairs were available from pts who received chemotherapy (CT) between PT & REC. CIN70 increased from PT to REC, DDRD (non-significantly) & PARPi7 decreased. 4/5 TP53 wildtype classified PT samples classified as mut in REC. The BRCA1/2 & DDRD-treatment interactions only held in pts who received CT before trial entry (table). The PARPi7-treatment interaction only held in CT naïve pts. In CT naïve pts, high CIN70 tumors suggested higher C RR as hypothesized. Restricted to the 149 PAM50 basal-like pts, results were non-significant but similar trends seen. Conclusions: In this trial of aTNBC, DDRD high pts with prior CT had better RR to D than C. A possible explanation for this unexpected result is selective pressure of adjuvant DNA damaging CT and selection for relative taxane sensitivity in those who recur despite a high DDRD score. The hypothesised CIN70 treatment interaction was observed in CT naïve pts. Our results suggest care is required in application of signatures to initial diagnostic material when predicting response to DNA damaging agents at REC particularly in pts with prior CT. [Table: see text]

Background: \ud We have previously shown that raised p-S6K levels correlate with resistance to chemotherapy in ovarian cancer. We hypothesised that inhibiting p-S6K signalling with the dual m-TORC1/2 inhibitor in patients receiving weekly paclitaxel could improve outcomes in such patients.\ud \ud Patients and methods: \ud In dose escalation, weekly paclitaxel (80 mg/m2) was given 6/7 weeks in combination with two intermittent schedules of vistusertib (dosing starting on the day of paclitaxel): schedule A, vistusertib dosed bd for 3 consecutive days per week (3/7 days) and schedule B, vistusertib dosed bd for 2 consecutive days per week (2/7 days). After establishing a recommended phase II dose (RP2D), expansion cohorts in high-grade serous ovarian cancer (HGSOC) and squamous non-small-cell lung cancer (sqNSCLC) were explored in 25 and 40 patients, respectively.\ud \ud Results: \ud The dose-escalation arms comprised 22 patients with advanced solid tumours. The dose-limiting toxicities were fatigue and mucositis in schedule A and rash in schedule B. On the basis of toxicity and pharmacokinetic (PK) and pharmacodynamic (PD) evaluations, the RP2D was established as 80 mg/m2 paclitaxel with 50 mg vistusertib bd 3/7 days for 6/7 weeks. In the HGSOC expansion, RECIST and GCIG CA125 response rates were 13/25 (52%) and 16/25 (64%), respectively, with median progression-free survival (mPFS) of 5.8 months (95% CI: 3.28–18.54). The RP2D was not well tolerated in the SqNSCLC expansion, but toxicities were manageable after the daily vistusertib dose was reduced to 25 mg bd for the following 23 patients. The RECIST response rate in this group was 8/23 (35%), and the mPFS was 5.8 months (95% CI: 2.76–21.25).\ud \ud Discussion: \ud In this phase I trial, we report a highly active and well-tolerated combination of vistusertib, administered as an intermittent schedule with weekly paclitaxel, in patients with HGSOC and SqNSCLC.\ud \ud Clinical trial registration: \ud ClinicialTrials.gov identifier: CNCT02193633.

Germline mutations in BRCA1/2 predispose individuals to breast cancer (termed germline-mutated BRCA1/2 breast cancer, gBRCA-BC) by impairing homologous recombination (HR) and causing genomic instability. HR also repairs DNA lesions caused by platinum agents and PARP inhibitors. Triple-negative breast cancers (TNBCs) harbor subpopulations with BRCA1/2 mutations, hypothesized to be especially platinum-sensitive. Cancers in putative 'BRCAness' subgroups - tumors with BRCA1 methylation; low levels of BRCA1 mRNA (BRCA1 mRNA-low); or mutational signatures for HR deficiency and those with basal phenotypes - may also be sensitive to platinum. We assessed the efficacy of carboplatin and another mechanistically distinct therapy, docetaxel, in a phase 3 trial in subjects with unselected advanced TNBC. A prespecified protocol enabled biomarker-treatment interaction analyses in gBRCA-BC and BRCAness subgroups. The primary endpoint was objective response rate (ORR). In the unselected population (376 subjects; 188 carboplatin, 188 docetaxel), carboplatin was not more active than docetaxel (ORR, 31.4% versus 34.0%, respectively; P = 0.66). In contrast, in subjects with gBRCA-BC, carboplatin had double the ORR of docetaxel (68% versus 33%, respectively; biomarker, treatment interaction P = 0.01). Such benefit was not observed for subjects with BRCA1 methylation, BRCA1 mRNA-low tumors or a high score in a Myriad HRD assay. Significant interaction between treatment and the basal-like subtype was driven by high docetaxel response in the nonbasal subgroup. We conclude that patients with advanced TNBC benefit from characterization of BRCA1/2 mutations, but not BRCA1 methylation or Myriad HRD analyses, to inform choices on platinum-based chemotherapy. Additionally, gene expression analysis of basal-like cancers may also influence treatment selection.

The concept of precision medicine has been around for many years and recent advances in high-throughput sequencing techniques are enabling this to become reality. Within the field of breast cancer, a number of signatures have been developed to molecularly sub-classify tumours. Notable examples recently approved by National Institute for Health and Care Excellence in the UK to guide treatment decisions for oestrogen receptors (ER)+ human epidermal growth factor receptor 2 (HER2)- patients include Prosigna® test, EndoPredict®, and Oncotype DX®. However, a population of still unmet need are those with triple negative breast cancer (TNBC). Accounting for 15–20% of patients, this population has comparatively poor prognosis and as yet no targeted treatment options. Studies have shown that some patients with TNBC respond favourably to DNA damaging drugs (carboplatin) or agents which inhibit DNA damage response (poly ADP ribose polymerase (PARP) inhibitors). Known to be a heterogeneous population, there is a need to identify further TNBC patients who may benefit from these treatments. A number of signatures have been identified based on association with treatment response or specific genetic features/pathways however many of these were not restricted to TNBC patients and as of yet are not common practice in the clinic.

IMPORTANCE: Current treatment cures most cases of early-stage, primary breast cancer. However, better techniques are required to identify which patients are at risk of relapse. OBJECTIVE: To assess the clinical validity of molecular relapse detection with circulating tumor DNA (ctDNA) analysis in early-stage breast cancer. DESIGN, SETTING, AND PARTICIPANTS: This prospective, multicenter, sample collection, validation study conducted at 5 United Kingdom medical centers from November 24, 2011, to October 18, 2016, assessed patients with early-stage breast cancer irrespective of hormone receptor and ERBB2 (formerly HER2 or HER2/neu) status who were receiving neoadjuvant chemotherapy followed by surgery or surgery before adjuvant chemotherapy. The study recruited 170 women, with mutations identified in 101 patients forming the main cohort. Secondary analyses were conducted on a combined cohort of 144 patients, including 43 patients previously analyzed in a proof of principle study. INTERVENTIONS: Primary tumor was sequenced to identify somatic mutations, and personalized tumor-specific digital polymerase chain reaction assays were used to monitor these mutations in serial plasma samples taken every 3 months for the first year of follow-up and subsequently every 6 months. MAIN OUTCOMES AND MEASURES: The primary end point was relapse-free survival analyzed with Cox proportional hazards regression models. RESULTS: In the main cohort of 101 female patients (mean [SD] age, 54 [11] years) with a median follow-up of 35.5 months (interquartile range, 27.9-43.0 months), detection of ctDNA during follow-up was associated with relapse (hazard ratio, 25.2; 95% CI, 6.7-95.6; P

e16513 Background: Ra-223 improves overall survival in patients with mCRPC, but is associated with increased risk of fracture when used in combination with abiraterone and prednisolone. We have assessed time to first new fracture in men with mCRPC receiving Ra-223 monotherapy, imaged using whole body MRI. Methods: In a prospective phase II study, patients with chemotherapy-naïve, bone mCRPC were randomised (1:1) to receive Ra-223 at 55 or 88 kBq/kg for 6 cycles, at 4-week intervals (REASURE; ISRCTN17805587). Whole body MRI was done at baseline, at cycles 2 and 4, and 1 month post-treatment. Subsequent imaging was done as clinically indicated. All scans were centrally reviewed to describe the time to first new fracture and characteristics of fractures. Time to new fracture was analysed using Kaplan Meier methods; comparisons of time to fracture between groups were based on log-rank tests. Results: 36 evaluable patients received a median of 6 cycles of Ra-223; scans were available for 35 patients. For these 35 patients, median age was 75 years (IQR: 73-80). 3 (9%) were receiving bone health agents at trial entry; 8 (23%) had received prior abiraterone or enzalutamide. 21 (60%) patients developed new fractures between randomisation and 2 years after completing treatment with radium-223. The spine was the most common location for fractures (14 patients). Median time to new fracture from randomisation was 10.8 months (95% CI: 6.2-18.2). Freedom from new fracture at 2 years post-randomisation was 21% (95% CI: 7 – 39%). Time to first new fracture was not associated with Ra-223 dose (55 kBq/kg: 10/18 patients experienced a fracture vs 88kBq/kg: 11/17; p = 0.93) or baseline use of bone health agents (3/3 vs 18/32; p = 0.09). Patients with Extent of Disease (EOD) ≥2 (defined as ≥6 metastatic sites/superscan) had earlier time to first new fracture compared to patients with EOD 1 (defined as < 6 metastatic sites) (11/18 vs 10/17; hazard ratio = 2.7, 95% confidence interval = 1.0 – 6.8; p = 0.04). Conclusions: New fractures are commonly seen on imaging in men with mCRPC during and after treatment with Ra-223 monotherapy. This observation supports treatment guidelines that recommend the use of bone health agents in men with mCRPC. Clinical trial information: ISRCTN17805587.

Background. Detection of circulating tumor DNA (ctDNA) after treatment of early stage breast cancer may identify molecular residual disease. In a prior proof-of-principle study we demonstrated that detection of ctDNA predicted relapse with high accuracy (Garcia-Murillas et al Science Trans Med 2015). We conducted an independent, prospective, multi-centre validation study. Methods. In this validation study, a cohort of 170 early stage breast cancer patients were recruited from five hospitals into two prospective sample collection studies. Patients were scheduled to receive standard chemotherapy, surgery +/- radiotherapy, adjuvant endocrine therapy and HER2 antibodies as appropriate. Plasma samples were collected for ctDNA analysis at baseline, post-surgery, three monthly for the first year of follow-up, and six monthly thereafter and shipped to a central lab for processing. Using previously established criteria, tumor was sequenced to identify somatic mutations that were tracked by digital PCR in DNA extracted from 4mls of plasma at all available time points. Buffy coat DNA was analysed at all time-points to control for clonal haematopoesis of indeterminate potential (CHIP) detection. The primary endpoint was to compare invasive disease free survival between patients with and without detection of ctDNA after treatment. A combined analysis of this validation study, and the prior proof-of-principle study, was also conducted to analyse secondary endpoints. Results. After tumor sequencing, 101 patients from the validation study had at least one mutation to track. At median 35.5 months follow-up, ctDNA was detected in plasma of 15.8% (16/101) patients. Detection of ctDNA strongly predicted relapse, hazard ratio 24.5 (95% CI 6.5 to 93.2, P In the combined analysis (N=144), lead-time between ctDNA detection and relapse was 10.7 months (95% CI 7.7-17.0). Six patients had a clinical relapse that was not detected by ctDNA prior to relapse. These patients had a distinct pattern of oligo-metastatic relapse, 3 patients with brain-only metastases (P=0.0068), 1 ovarian oligo-metastasis and 2 local disease recurrence. The level of ctDNA in baseline plasma, prior to treatment, was associated with tumor subtype, highest in triple negative breast cancer (P=0.0036). Conclusion. Detection of ctDNA after treatment is associated with a high risk of future relapse in early-stage breast cancer. Prospective studies are required to assess the potential of molecular residual disease detection to guide adjuvant therapy. Citation Format: Turner N, Garcia-Murillas I, Chopra N, Comino-Mendez I, Beaney M, Tovey H, Cutts R, Swift C, Kriplani D, Afentakis M, Hrebien S, Walsh G, Johnston S, Ring A, Russell S, Evans A, Skene A, Wheatley D, Dowsett M, Smith I. Molecular residual disease detection with circulating tumor DNA analysis predicts relapse in patients with early stage breast cancer [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P4-01-01.

547 Background: Platinum-based combination chemotherapy regimens are used in the treatment of carcinoma of the penis, but toxicity limits their value for patients with metastatic disease. This trial aims to define both the toxicity and the rate of disease control for the non-platinum cytotoxic agent Vinflunine. Methods: A phase II single-arm trial was designed to demonstrate a clinical benefit rate of at least 40% and to exclude a rate of less than 15% (p0 = 0.15, p1 = 0.40, α = 0.05, β = 0.80, Fleming-A’hern exact design). 22 evaluable patients were required. Key eligibility criteria included measurable, histologically-proven squamous cell carcinoma of the penis staged as M1; or M0, Tx, N3; or M0, Tx, N2 and deemed inoperable by multidisciplinary team; or M0, T4 any N. Patients were required to have ECOG performance status of 0, 1 or 2 and adequate hepatic and renal function. Treatment comprised four 21-day cycles of vinflunine (320mg/m2) with RECIST v1.1 restaging following cycle 4 (response primary endpoint). Patients deemed to be benefitting from treatment were permitted to continue vinflunine at the discretion of the treating clinician until progression or unacceptable toxicity. Results: 25 patients were recruited from 8 UK centres between June 2014 and May 2017. Median age was 68 years; 19 patients had metastatic (M1) disease. All patients have completed trial treatment and primary endpoint assessment. Data cleaning for the primary analysis is currently in progress, with the snapshot for the primary analysis due in October 2017 and primary analysis to be presented to the trial oversight committees in November 2017. Conclusions: It is hoped that single-agent vinflunine will be associated with a favourable toxicity profile combined with meaningful clinical responses. The results will be available for presentation at the meeting. Clinical trial information: NCT02057913.

Background Inhibition of COX-2 has been shown to attenuate the metastatic process in pre-clinical models of human breast cancer (BC). The primary aim of this study was to assess the effect of 2 years adjuvant therapy with the COX-2 inhibitor celecoxib compared with placebo in HER2-ve primary BC patients. Patients & Methods Patients were randomised in a 2:1 ratio to receive celecoxib 400mg once daily or placebo for 2 years. Patients had to have completely resected BC with prior local and systemic adjuvant treatment according to local practice. Concurrent radiotherapy was permitted and hormone receptor +ve patients received endocrine therapy according to local practice. Patients with HER2+ or node negative, T1 and grade 1 disease were excluded. Median age of patients was 55 years (IQR: 49-63). 50% of patients had tumours >2cm; 42% were grade 3; 48% had node +ve disease. According to local assessment 73% were ER/PgR +ve. Primary endpoint was Disease Free Survival (DFS); defined as time from randomisation to date of first event, with events contributing to analysis defined as recurrence (distant/local), new primary BC (ipsilateral/contralateral) and death. Secondary endpoints included Overall Survival (OS), toxicity, cardiovascular mortality and incidence of second primaries. Subgroup analysis by hormone receptor status was pre-planned. Survival endpoints are analysed using Cox-proportional hazards and log-rank tests; restricted mean survival is used where proportional hazards do not hold. Results Between January 2007 and November 2012, 2639 patients were randomised (1763 celecoxib; 876 placebo) from 181 centres across the UK and Germany. At 13th April 2017, median follow up was 60 months (IQR: 48-72) with 428 DFS events reported. Unadjusted survival analysis results are presented below, with hazard ratio 5 year survival estimate (95% CI)Hazard ratio (95% CI)p-valueDFS (all patients) Celecoxib83% (81, 85)1.02 (0.83 – 1.24)0.88Placebo83% (80, 86)1- DFS within ER+ Celecoxib87% (85, 89)0.89 (0.69 – 1.16)0.40Placebo86% (83, 89)1- DFS within ER- Celecoxib72% (68, 76)1.17 (0.85 – 1.61)0.33Placebo75% (69, 80)1- OS (all patients) Celecoxib90% (88, 91)0.97 (0.75 – 1.25)0.81Placebo90% (88, 92)1- The interaction between ER status and treatment was not significant; p=0.36. In the celecoxib and placebo groups there were 17 and 8 deaths respectively in patients who had not relapsed. These were due to cardiac (n=3; 2) and other (n=14; 6) in the celecoxib and placebo groups respectively; none were GI related. In total 304 serious adverse events were observed in 265 patients (186/1763 celecoxib; 79/876 placebo). In the celecoxib and placebo groups respectively these were related to cardiac (n=12; 7), GI (n=9; 2) and other (n=193; 81). Work is ongoing to determine whether a subset of ER+ patients whose primary tumours show the characteristics of a COX-2 signature receive greater benefit from celecoxib. Conclusions There is no benefit of celecoxib in the ITT population. Further exploratory studies focussing on the ER+ subpopulation are ongoing. Celecoxib treatment is not associated with significant toxicity when compared to placebo in this population of BC patients. Citation Format: Coombes RC, Tovey H, Kilburn L, Mansi J, Palmieri C, Bartlett J, Hicks J, Makris A, Evans A, Loibl S, Denkert C, Murray E, Grieve R, Coleman R, Schmidt M, Klare P, Rezai M, Rautenberg B, Klutinus N, Rhein U, Mousa K, Ricardo-Vitorino S, von Minckwitz G, Bliss J. A phase III multicentre double blind randomised trial of celecoxib versus placebo in primary breast cancer patients (REACT – Randomised EuropeAn celecoxib trial) [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr GS3-03.

2573 Background: The phosphatidylinositol 3-kinase (PI3K) pathway is commonly mutated in cancer. Tas is a selective β-isoform-sparing PI3K inhibitor with improved therapeutic index compared to pan-PI3K inhibitors. Palb is a CDK4/6 inhibitor now standard of care in combination with endocrine therapy (ET) in hormone receptor positive breast cancer. Combination of Tas, Palb and ET is synergistic in preclinical models. Methods: This investigator-initiated study investigated safety and tolerability, pharmacokinetics (PK), PD and antitumor activity of Tas+Palb, with addition of ET in dose expansion. Pts were enrolled in 3+3 dose escalation design. Tas was given continuously or 3-weeks-on, 1-week-off (3/1), Palb was given on 3/1 schedule. PD studies included analyses of platelet-rich plasma (PRP) (n = 20) and paired tumor biopsies (n = 5). Serial circulating tumor DNA was monitored in pts with PIK3CA mutations. Results: 24 pts were treated, 22 with Tas+Palb, 2 with Tas+Palb+fulvestrant(ful); M/F 11/13, median lines prior therapy 4. Treatment was well tolerated with mainly G1-2 toxicities. Most frequent G3 toxicities were neutropenia (5/24), thrombocytopenia (5/24) and rash (5/24), with no G4/5 toxicities. Two pts had dose-limiting toxicities (DLT) at DL2. No DLTs were observed at DL4, although pts experienced delayed neutrophil recovery. PK was linear and comparable with monotherapy. At 125mg Palb, significant decreases in pAKT and pGSK3β in PRP confirmed PI3K target inhibition. Two pts with PI3KCA H1047R mutant breast cancers have ongoing RECIST partial response; 1 pt with PIK3CA E542K colorectal cancer had stable disease for 20 weeks. Conclusions: Tas+Palb is well tolerated with evidence of PD and antitumor activity. Dose expansion including recruitment to triplet Tas+Palb+ful and Tas+Palb+letrozole is ongoing with continuous Tas 2mg QD, and Palb 100mg QD on 3/1 schedule, increasing to 125mg after cycle 1 in absence of myelosuppression. Clinical trial information: NCT02389842. [Table: see text]

2571 Background: In ovarian cells isolated from ascites, p-S6K levels were found to correlate with resistance to chemotherapy. We hypothesised that inhibiting p-S6K signalling with dual m-TORC1/2 inhibitor vistusertib (V) in addition to paclitaxel (P) would improve outcomes of patients with high-grade serous ovarian cancer (HGSOC). Methods: In the dose escalation part, weekly P 80mg/m2IV (6/7 weeks) was evaluated in combination with two schedules of V; Schedule A: V (25, 50 or 75mg) BID PO on day(D) 1-3/week and Schedule B: V (75 or 100mg) BID PO D1-2/week. This was followed by an expansion cohort in 25 HGSOC patients. Results: Dose limiting toxicities in Schedule A were fatigue and mucositis and in Schedule B were diarrhoea, rash and fatigue. The AUC, Cmax and half-life of V in the 50mg-cohort were 2821ng.hr/ml, 926ng/ml and 3hrs, comparable to single agent studies. PD analysis (from six 50mg-cohort patients) in platelet-rich plasma showed increased phosphorylation of Ser473 AKT following P induction (1.4 fold, p = 0.1378). Following addition of V to P, phosphorylation levels 4hrs post-treatment with V fell significantly to 53% of pre-dose levels (p = 0.0495). This was 61% lower than the corresponding time point following P alone. Based on toxicity, pharmacokinetic and PD evaluation, recommended phase 2 dose was established as P 80mg/m2 D1 and V 50mg BID D1-3 for 6/7 weeks. In the HGSOC expansion, 96% of patients had relapsed within 12 months of last platinum therapy and 100% had received previous paclitaxel, with a median of 3 previous lines of treatments. RECIST and GCIG CA125 response rates were 13/25 (52%) and 15/25 (60%) respectively, with median progression free survival of 5.5 months. MC was performed on archival tumor tissue of 24/25 HGSOC expansion cohort patients, with the most common mutations occurring in p53 (100%), BRCA (17%), and MUC16 (17%). ATM mutations occurred in 17% (n = 4), 3 of whom had a response. Conclusions: We report a highly active combination of paclitaxel with an intermittent schedule of vistusertib in patients with HGSOC. This combination is now being evaluated in a randomised controlled trial for this indication. Clinical trial information: NCT02193633.

2506 Background: RO5126766 is a potent RAF and MEK inhibitor with activity in xenografts models of RAS and RAF-mutated cancers. We present data from the RAS/RAF-mutated advanced solid tumor cohort and the initial results for the multiple myeloma (MM) cohort. Methods: Patients with KRAS, NRAS or BRAF-mutant tumours were treated with RO5127566 using a novel schedule:4mg twice weekly in 4-week cycles. For MM patients, it was given 3 weeks out of 4 and co-administration of weekly dexamethasone was authorised. Response assessment was completed using RECIST 1.1 criteria for solid tumours and the International Myeloma Working Group (IMWG) criteria were used for MM. Results: A total of 20 patients with solid tumours (10 NSCLC, 5 gynaecological cancers and 5 miscellaneous cancers) and 1 MM patients were evaluable. Among the 10 KRAS-mutant NSCLC patients, tumour regression was seen in 6/10 (60 %), of which 3/10 (30 %) were partial responses. Two of these patients had maintained response for over 1 year and one patient is still on study after 30 cycles. Of the gynaecological cancers, 3/5 patients (60%) achieved a partial response ( KRAS-mutant endometrial and ovarian cancer and BRAF-mutant ovarian). Of these patients, 1 of the KRAS mutants had received 2 previous lines of MEK inhibitors and the BRAF mutant had previously received a BRAF inhibitor. In the miscellaneous group, 4 patients with colorectal cancer (2 BRAF and 2 NRAS) and 1 patient with NRAS-mutant melanoma were treated and none responded. Two patients with MM have been treated so far (1 KRAS, 1 KRAS+NRAS). The one evaluable patient has had an IMWG partial response (PR) after 1 cycle (FLC-λ from 324 mg/L to 161mg/L, ratio 0.03 to 0.08) without concomittant dexamethasone. This patient was previously treated with an immunomodulatory drug, a proteasome inhibitor and two ASCTs. Conclusions: RO5126766 has shown exciting preliminary activity across a wide range of RAS- and RAF-mutated malignancies, with significant response rates in lung and gynaecological cancers. To our knowledge, the PR seen in our MM patient represents one of the first responses to a single-agent RAF/MEK inhibitor in multiple myeloma in a trial context. Clinical trial information: NCT02407509.

135 Background: Activation of the PI3K/AKT/mTOR pathway may contribute to resistance to androgen receptor targeted therapies in metastatic CRPC (mCRPC). The phase I/II RE-AKT trial (NCT02525068) investigates the safety and activity of enzalutamide (enza) in combination with the AKT inhibitor, AZD5363, in patients (pts) with mCRPC. Results of the phase I run-in are reported. Methods: mCRPC pts progressing after 1-2 lines of taxane chemotherapy and at least 12 weeks (wks) of abiraterone or enza were treated with enza (160mg od) and AZD5363 bid 4-days on, 3-days off, in a 3+3 dose escalation design. Co-primary endpoints were to assess toxicity (CTCAE), and identify the recommended phase II dose (RP2D) of AZD5363; antitumour activity and pharmacokinetics (PK) were secondary endpoints. Response was assessed by PSA, RECIST v1.1 and circulating tumor cell (CTC) conversion. Pts were considered evaluable for response if they completed 12 wks of treatment. Results: 16 pts were enrolled between 12/2014 & 04/2016 with 15 receiving treatment. At the AZD5363 320mg dose 3 pts were treated with no dose limiting toxicity (DLT). At the AZD5363 480mg dose, 5 pts were treated with 2 DLTs of grade (G) 3 maculopapular rash (MPR) related to AZD5363. An intermediate dose level of AZD5363 400mg was selected with 7 pts treated. 1 pt withdrew consent prior to completing the DLT window. 1 DLT of G3 MPR occurred and this dose was selected as the RP2D. Non-DLT treatment related (TR) G3/4 adverse events (AEs) were hyperglycaemia (n = 4, 26.7%), neutropenia (n = 1, 6.7%) & diarrhea (n = 1, 6.7%). All other TR AEs were G1 or G2, with diarrhea (n = 9, 60%), anorexia (n = 8, 53.3%) & nausea (n = 7, 46.7%) being most common. Of the 10 pts who completed 12 wks of treatment, 3 met at least one of the criteria for response. 1 pt (AZD5363 320mg) who had previously progressed on enza exhibited RECIST v1.1 partial response, > 50% PSA response, and CTC conversion by wk 13. Enza decreased AZD5363 PK exposure; robust modulation of pS6, pGSK3b and pPRAS40 was demonstrated. Conclusions: AZD5363 at the RP2D of 400mg bid 4 days on, 3 days off combined with enza 160mg od is safe and tolerable. Antitumor activity is reported, suggesting that AZD5363 may be able to overcome resistance to enza. Clinical trial information: NCT02525068.

2582Background: RO5126766 is a novel MEK inhibitor with functional RAF inhibition. A dose escalation Phase 1 study, comparing 2 intermittent schedules, has previously been reported, with a recommen...

TNT is a trial comparing carboplatin with docetaxel for advanced TN or BRCA1/2 BC patients. TNBC is heterogeneous; median progression-free survival (PFS) is short but some patients have prolonged PFS following treatment. BRCA1/2 patients were hypothesised to respond better to carboplatin. This interaction, with the heterogeneous population, was expected to cause a failure of PH assumptions required for Cox-PH analysis. Therefore, TNT required alternative analysis methods.

1019 Background: The majority of triple negative breast cancers are of basal-like subtype (BLBC). There is uncertainty about concordance of intrinsic subtypes and ROR scores by PAM50 between matche...

Introduction: Subgroups within sporadic triple negative breast cancers (TNBCs) appear to share impaired DNA damage response mechanisms with BRCA1/2 mutation-associated breast cancers. This has been hypothesised to confer particular sensitivity to DNA-damaging platinum chemotherapy. The TNT trial, a randomized phase III trial in women with metastatic or recurrent locally advanced TNBC or BRCA1/2 mutation-associated breast cancer, aimed to test this hypothesis and examine treatment effect in biological subgroups. Patients & Methods: Eligible patients had either ER-, PR-, HER2- breast cancer or were known BRCA1/2 carriers (any ER/PR/HER2). Patients were randomized (1:1) to receive either C (AUC 6 q3wk) or D (100mg/m2 q3wk) for 6-8 cycles or until disease progression if sooner and could cross over to the alternative treatment on confirmed progression. Ineligible patients included those who had ECOG performance status >2, received adjuvant taxane therapy in the last 12 mths, any previous treatment with a platinum chemotherapy, or previous non-anthracycline chemotherapy for metastatic disease. For consenting patients a blood sample and archived tissue samples were obtained for BRCA1/2 genotyping and central biomarker analysis (primary tumour, lymph nodes and recurrent tumour biopsy if available) of subtypes within TNBC and biomarkers of DNA repair deficiency. The primary endpoint was RECIST objective tumour response up to cycle 6 of randomised treatment. Secondary endpoints included toxicity, progression free survival (PFS), time to progression and overall survival. TNT aimed to detect a 15% improvement in ORR with C compared to D, with planned target sample size range of 370-450 depending on assumed ORR in D patients (2-sided α=0.05, power=90%). 376 (188 C, 188 D) were recruited from 74 UK centres between Apr 08 and Mar 14. Results: A snapshot of the data was taken on 30/5/14 at which point 336 (89.4%) patients had experienced a PFS event, with overall median PFS time of 4.4 mths. Median age of patients was 55 yrs (IQR 48-63). 366/376 (97%) patients had TNBC of whom 18 were also known BRCA1/2 mutation carriers, with the remaining 10 patients receptor +ve and BRCA1/2 carriers. 338/376 (90%) had metastatic and 38/376 (10%) recurrent locally advanced disease. 53% had liver or lung metastases affecting the parenchyma and 34% had received previous adjuvant taxane therapy. Median time from initial diagnosis to entering TNT was 2.2 yrs (IQR 1.5-3.5). Primary tumour tissue has currently been received for 277 patients, blood from 286 patients and recurrent tumour tissue from 85 patients. Discussion: TNT will report evidence on the activity of single agent platinum chemotherapy compared with single agent taxane in patients with TNBC and BRCA1/2 associated breast cancer. Correlative analyses of BRCA1/2 mutation status, subtypes and DNA repair biomarkers will also be reported. TNT will be the first randomised trial to report the activity of platinum compared with standard chemotherapy within TNBC subtypes and in relation to BRCA1/2 mutation status and DNA repair biomarkers. Safety, tolerability and response to crossover treatment will also be presented. Citation Format: Andrew Tutt, Paul Ellis, Lucy Kilburn, Cheryl Gilett, Sarah Pinder, Jacinta Abraham, Sophie Barrett, Peter Barrett-Lee, Stephen Chan, Maggie Cheang, Mitch Dowsett, Lisa Fox, Patrycja Gazinska, Anita Grigoriadis, Alexander Gutin, Catherine Harper-Wynne, Matthew Hatton, Sarah Kernaghan, Jerry Lanchbury, James Morden, Julie Owen, Jyoti Parikh, Peter Parker, Nazneen Rahman, Rebecca Roylance, Adam Shaw, Ian Smith, Rose Thompson, Kirsten Timms, Holly Tovey, Andrew Wardley, Gregory Wilson, Mark Harries, Judith Bliss. The TNT trial: A randomized phase III trial of carboplatin (C) compared with docetaxel (D) for patients with metastatic or recurrent locally advanced triple negative or BRCA1/2 breast cancer (CRUK/07/012) [abstract]. In: Proceedings of the Thirty-Seventh Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2014 Dec 9-13; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2015;75(9 Suppl):Abstract nr S3-01.