Abstract
Tumors deficient in DNA mismatch repair are known to display increased susceptibility to immune checkpoint inhibitors due to accumulation of DNA damage and increased neoantigen load. This suggests that deficiency in the BRCA-related DNA repair mechanism may also be a surrogate marker for immunotherapy response. The aim of this study was to examine the efficacy of the immune checkpoint inhibitor, nivolumab, in women with BRCA gene mutations and recurrent müllerian cancer. This retrospective case series followed six BRCA carriers who received nivolumab monotherapy (3.0 mg/kg, intravenous, day 1 and 15, every 4 weeks) as salvage therapy for recurrent epithelial ovarian (n = 5) and fallopian tubal (n = 1) cancers. Toxicity, treatment response, and survival were examined. Median age was 57 (range 51-64). BRCA1 and 2 mutations were equally distributed. All had high-grade serous histology, and all but one had advanced-stage disease at initial diagnosis. The majority had platinum-resistant disease (n = 4). All received salvage therapy prior to nivolumab therapy (median 3 lines), including PARP inhibitors (n = 3). The median number of nivolumab treatment cycles was 9, including 2 women receiving 18 cycles. Three women developed nivolumab-related toxicities, most commonly grade 2 hypothyroidism (n = 2). Median follow-up time was 13.4 months, and there were 3 complete responses, 1 partial response, and 2 patients with progressive disease. Objective response rate was 67% (4 out of 6). In conclusion, our study suggests that nivolumab monotherapy is well-tolerated and may be an effective salvage therapy for BRCA mutation carriers with recurrent epithelial ovarian, fallopian tubal, and primary peritoneal cancers.