TPS1112 Background: Patients with metastatic triple negative breast cancer (mTNBC) have limited treatment options. Recent studies with a PD-L1 inhibitor and taxane based chemotherapy have demonstrated an increase in median progression free survival (PFS) in mTNBC. While taxanes target microtubules, platinum agents directly alkylate DNA and may generate additional neoantigens to enhance anti-tumor immunity via immune checkpoint inhibition. In this study, we are evaluating the combination of carboplatin with and without atezolizumab in patients with mTNBC. Serial biopsies are poised to help elucidate biological differences in responders and nonresponders. As optimal timing of adding checkpoint inhibition to chemotherapy is debatable, the randomized, crossover design will give insight into whether priming mTNBCs with DNA damaging chemotherapy results in cellular and immune changes that lead to a greater likelihood of response. Methods: This is a randomized phase II multicenter study at seven sites within the Translational Breast Cancer Research Consortium (TBCRC). Patients with mTNBC, ECOG 0-1, and 0-1 prior regimens for mTNBC are eligible. 106 patients will be randomized 1:1 to receive atezolizumab 1200 mg plus carboplatin AUC 6 (n = 53; Arm A) or carboplatin AUC 6 alone (n = 53; Arm B) every 3 weeks until intolerable toxicity or disease progression occurs. Patients receiving carboplatin alone have the option to cross over to atezolizumab upon progression (Arm Bx). Patients will undergo clinical assessment every cycle, and tumor assessment every 3 cycles with CT scan of the chest, abdomen, and pelvis and bone scan. Core biopsies of a metastatic lesion are performed at baseline and at progression. The primary endpoint is median progression free survival (PFS) with 95% confidence intervals based on RECIST 1.1. The sample size of 106 with 1:1 randomization is powered to detect a 1.5-month difference in PFS between arms (α = 0.10, β = 0.20). Secondary endpoints include overall response rate (ORR), duration of response (DOR), clinical benefit rate, and overall survival. The PFS, ORR, and DOR will also be measured by irRECIST to account for delayed effects of atezolizumab on tumor burden. The quantification of tumor infiltrating lymphocytes (TILs) will study the prognostic effects of TILs on PFS in patients receiving atezolizumab. Biopsy-derived PD-L1 expression by IHC and RNA-seq will assess treatment-induced changes, define triple-negative subtypes, and evaluate for resistance mechanisms. To date, 89 of 106 patients are enrolled. Clinical trial information: NCT03206203 .
Real-world effectiveness outcomes in patients diagnosed with metastatic triple-negative breast cancer
