PARP inhibitors decrease response to subsequent platinum-based chemotherapy in patients with BRCA mutated ovarian cancer.

To determine the effect of poly-adenosine ribose phosphatase inhibitors (PARPi) on the response to subsequent platinum-based chemotherapy (PBC) in patients with recurrent, platinum-sensitive BRCA-mutated epithelial ovarian, peritoneal, or fallopian cancer (BRCAm EOC). This is a retrospective, single-institution cohort study of patients with BRCAm EOC who received retreatment with PBC. The PFS of patients with BRCAm EOC to 2nd or 3rd PBC with and without a prior PARPi was determined. Additionally, we compared the PFS to subsequent PBC following a prior PARPi for BRCAm and non-BRCAm. One hundred and fifteen patients with BRCAm EOC received a 2nd PBC and 55 received a 3rd PBC. The median PFS was 2.3 and 2.4 times longer, respectively for patients who did not receive a PARPi, (2nd P = 0.005, 3rd P < 0.001). Among 20 PARPi exposed patients with BRCAm EOC the PFS to a 2nd or 3rd PBC was worse at 8.0 months vs. 19.1 months HR 4.01 [2.25,7.16], P < 0.001. Following PARPi exposure the PFS for patients with BRCAm EOC was similar for patients with platinum-free intervals of 6-12, 12-24 and >24 months. Following PARPi exposure the PFS was similar for patients with BRCAm EOC and non BRCAm EOC. Among patients with BRCAm EOC PARPi exposure significantly reduced PFS following 2nd and 3rd PBC. PARPi exposure nullifies established prognostic factors (i.e. platinum-free interval and BRCA mutational status) in platinum-sensitive recurrent ovarian cancer.