Pembrolizumab with low dose carboplatin for recurrent platinum resistant ovarian, fallopian tube, and primary peritoneal cancer-interim results.

Abstract

5519 Background: Pembrolizumab has shown activity in advanced recurrent ovarian cancer (AOC) with an 8% response rate and median progression-free survival (PFS) of 2.1 months reported in KEYNOTE-100. Because platinum chemotherapies also induce T cell proliferation and enhance tumor cell recognition through PD-1/PD-L, we assessed the safety and activity of pembrolizumab with carboplatin in platinum resistant AOC. Methods: Key eligibility criteria for this Phase 1/2 single arm trial were platinum resistant AOC, fallopian tube, or peritoneal cancer, progression after subsequent systemic therapy, and ECOG PS 0-1. Pembrolizumab 200mg was given on Day 1 and carboplatin AUC 2 on Day 8 and 15 of a 3 week cycle until progression, unacceptable toxicity, or consent withdrawal. Imaging was done before cycles 4 and 8, then every 3 months and unconfirmed objective response assessed by blinded independent review per RECIST 1.1. Adverse events (AEs) were reported per Common Terminology for Adverse Events v5.0. PD-L1 expression was assessed by immunohistochemistry. Results: 27 patients (median age: 64) had received a median of 5 (range: 2-9) prior lines of systemic therapy, which included bevacizumab in 74% of patients. The most common treatment related (TR) AEs were lymphopenia (18%) and anemia (9%). The majority of TR AEs were grade 1 or 2 (93%). 6% of AEs were grade 3 with lymphopenia the most common. Two grade 4 AEs were neutropenia and lymphopenia. Of 23 patients evaluable for best objective response, 13.0% (95% CI, 2.7-33.6) had partial response (PR), 65.2% (95% CI, 42.7-83.6) had stable disease (SD), and 21.7% (95% CI, 7.4-43.7) had progression. 7 of the 23 evaluable patients (30.4%) had archival tumor with modified percent scoring ≥5 for PD-L1 and all achieved PR (3/7, 42.8%) or SD (4/7, 57.2%). Overall median PFS was 4.6 months (95% CI, 2.7-6.2). Rate of PFS at 6 months was 40.4% (95% CI, 25.5-65.5). Median follow-up is 6.2 months and PFS is based on current data, but 8 patients remain on study and estimates will be updated. Conclusions: Pembrolizumab with low dose carboplatin was well tolerated and showed activity in heavily pretreated platinum resistant AOC. Survival and biomarker analyses are ongoing. Clinical trial information: NCT03029598.