Carboplatin with or without nivolumab in metastatic triple-negative breast cancer: a randomized phase II trial

This multi-institutional randomized phase II clinical trial (NCT03414684) investigated the efficacy and safety of carboplatin plus nivolumab compared to carboplatin in metastatic triple-negative breast cancer (mTNBC). The primary endpoint was progression-free survival (PFS) in a modified intention-to-treat (mITT) population of patients with chemotherapy-naïve (i.e., first-line) mTNBC. Secondary endpoints included overall survival (OS), confirmed objective response rate, confirmed clinical benefit rate, time to and duration of confirmed objective response, safety, and tolerability. Clinical outcomes were evaluated in the PD-L1-positive subgroup ( ≥ 1% immune cells; SP142 clone) per central review. Biospecimens were collected for correlative analyses. 75 patients were enrolled and treated between 2/2018-9/2020. Among the mITT population (n = 62), median PFS was 4.2 months with carboplatin plus nivolumab vs 5.5 months with carboplatin. Median OS did not significantly differ between arms (16.8 vs 11.1 months, respectively). In PD-L1-positive mTNBC patients (n = 24), median PFS was 8.3 vs 4.7 months; median OS was 17.6 vs 10.7 months. Grade ≥3 adverse events occurred in 56.8% of patients in the combination arm and 65.8% in the carboplatin arm. Carboplatin plus nivolumab did not significantly improve PFS compared to carboplatin in patients overall; however, a trend toward improved outcomes was observed in PD-L1-positive mTNBC patients. High mutational burden, interferon-gamma signaling, early circulating tumor DNA reduction, low baseline serum thymidine kinase activity, and urea cycle dysregulation in the microbiome emerged as potential predictors of response to immune checkpoint inhibitors with platinum.