Background:

In patients with TNBC, following standard neoadjuvant chemotherapy, residual disease (RD) is correlated with poor prognosis and 50% relapse within 5 years [1]. PARTNER is a neoadjuvant clinical trial which randomises TNBC and gBRCAm patients to carboplatin and paclitaxel +/- olaparib followed by anthracycline-based chemotherapy. Patients with RD after neoadjuvant treatment in this trial also face poorer survival outcomes, due to the paucity of treatment options. PARTNERING, develops a new strategy using novel agent combinations as an alternative pathway for patients with RD within the PARTNER trial.

Methods: PARTNERING is a phase II open label, sub-study with a two-stage Simon design with biomarker guided treatment cohorts open only to patients in the PARTNER trial. A maximum of 15 patients will be included in each cohort. Patients with RD > 10% tumour cellularity (TC) on biopsy after neoadjuvant therapy will be eligible. Patients who have no tumour cells or < 10% TC, and those with progressive disease will be excluded. Allocation of patients into the cohorts will be based on tumour infiltrating lymphocytes (TILs) expression either on diagnostic or post treatment biopsy. Patients with tumours with TILs score ≤20% are considered “non-immunogenic” They will be stratified according to HRD status and allocated to receive a cell cycle checkpoint inhibitor + olaparib. Patients with a TILs score >20% are considered “immunogenic” and will be allocated to receive an immune checkpoint inhibitor with olaparib or a cell cycle checkpoint inhibitor.

Primary outcome measure is pCR / MRD rate at surgery after the administration of 2 cycles / 8 weeks of a combination of new agents. The rate of conversion to pCR/MRD will be correlated with TC, TILs, BRCA and homologous recombination deficiency (HRD) status, Ki67% and previous olaparib treatment.

Progress:The PARTNERING pathway in the PARTNER trial will be open late 2018.

Citation Format: Abraham JE, Vallier A-L, Qian W, Machin A, Grybowicz L, Thomas S, Weiss M, Harvey C, McAdam K, Hughes-Davies L, Roberts A, Provenzano E, Pinilla K, Roylance R, Copson E, Armstrong A, McMurtry E, Tischkowitz M, Earl HM. PARTNERING / PARTNER : Phase II sub-study to establish if the addition of combinations of new agents (olaparib, cell cycle and immune checkpoint inhibitors) can improve the rate of pathological complete response (pCR) and minimal residual disease (MRD) in triple negative breast cancer (TNBC) and / or germline BRCA mutated (gBRCAm) patients with evidence of residual disease after PARTNER therapy [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 OT3-01-02.