Abstract OT2-24-01: PARTNER: Randomised, phase II/III trial to evaluate the safety and efficacy of the addition of olaparib to platinum-based neoadjuvant chemotherapy in triple negative and/or germline BRCA mutated breast cancer patients

Abstract Background: Triple Negative Breast Cancers (TNBC) are a biologically diverse and aggressive subgroup lacking targeted therapy. Germline BRCA (gBRCA) breast cancer and TNBC share some phenotypic and molecular similarities, with 10%-20% of TNBC patients having gBRCA mutations. Homologous recombination deficient tumours are particularly sensitive to PARP inhibitors such as olaparib (Lynparza). It has been shown that adjuvant olaparib for patients with high-risk, HER2-negative early breast cancer and gBRCA pathogenic or likely pathogenic variants after adjuvant or neoadjuvant chemotherapy significantly improves 3-year invasive and distant disease-free survival compared to placebo (OlympiA). Aim: To establish if the addition of olaparib to neoadjuvant platinum based chemotherapy for basal TNBC and/or gBRCA breast cancer is safe and improves efficacy (pathological complete response (pCR) rate). Trial design: 3-stage open label randomised phase II/III trial of neoadjuvant paclitaxel and carboplatin +/- olaparib, followed by clinicians' choice of anthracycline regimen. Stage 1 and 2: Randomisation (1:1:1) to either control (3 weekly carboplatin AUC5/weekly paclitaxel 80mg/m2 for 4 cycles) or one of two research arms with the same chemotherapy regimen but with two different schedules of olaparib 150mg BD for 12 days. Stage 3: Randomisation (1:1) to either control arm or to the research arm selected in stage 2. End-points: Stage 1: Safety; Stage 2: Schedule selection using pCR rate and completion rate of olaparib using a “pick-the-winner” design. Stage 3: pCR rate. This trial includes an optional pathway (PARTNERING) aiming to establish if the addition of new agents (ATR inhibitor and PDL1 inhibitor) can improve response in those patients with evidence of residual disease before surgery. Eligibility criteria: Aged 16-70; histologically confirmed invasive breast cancer; ER-negative, HER2-negative with TNBC basal phenotype or gBRCA positive, HER2-negative irrespective of hormone status; clinical stage T1-4 N0-2; performance status 0-1; treatment commenced within 6 weeks of diagnostic biopsy; biomarker scores: TILs, CK 5/6, EGFR +/- AR. Statistical methods: The recruitment of TNBC non-gBRCA and gBRCA patients is independent. Enrichment design is applied with an overall significance level 0.05(α) and 80% power. A minimum of 780 patients will be included to detect an absolute improvement of 15% (all patients and the TNBC non-gBRCA cohort) and 20% (gBRCA patients) by adding olaparib to platinum based chemotherapy. It is planned to recruit a minimum of 188 gBRCA patients. A maximum of 15 patients will be allocated into each PARTNERING cohort. Present accrual: Recruitment commenced 27 May 2016 and 678 patients from 30 sites have been accrued to date. The IDSMC reviewed the trial after Stages 1 and 2 and recommended to continue the trial without change. Data analysis for Stage 2 revealed no safety concerns and research arm 2 (olaparib on day 3 to day 14) was selected. Stage 3 Phase I recruitment is in progress (recruiting TNBC non-gBRCA and gBRCA patients) and we anticipate moving to Phase II (recruiting gBRCA patients only) by early 2022. Four patients have been accrued to the PARTNERING optional pathway to date. The trial is open and enrolling patients to UK and international sites. Contact information: partner@addenbrookes.nhs.uk Citation Format: Lynsey M Drewett, Karen A Pinilla, Louise Grybowicz, Jerome Wulff, Alimu Dayimu, Nikolaos Demiris, Jessica Martin, Camila Maida de Pontes, Nicola Johnson, Caron Harvey, Erdem Demir, Kimberley St John Green, James Jones, Gemma Young, Anne-Laure Vallier, Wendi Qian, Andrea Machin, Karen McAdam, Rebecca Roylance, Ellen R Copson, Anne Armstrong, Nicola Levitt, Elena Provenzano, Marc Tischkowitz, Emma McMurtry, Helena Earl, Jean E Abraham. PARTNER: Randomised, phase II/III trial to evaluate the safety and efficacy of the addition of olaparib to platinum-based neoadjuvant chemotherapy in triple negative and/or germline BRCA mutated breast cancer patients [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 OT2-24-01.