ROCSAN trial (GINECO-EN203b/ENGOT-EN8): A multicentric randomized phase II/III evaluating dostarlimab in combination with niraparib versus niraparib alone compared to chemotherapy in the treatment of endometrial/ovarian carcinosarcoma after at least one line of platinum based chemotherapy.

Abstract

TPS5604 Background: Gynecological carcinosarcomas (CS) are rare and highly aggressive tumors with a 5-year overall survival (OS) < 10%. After initial treatment majority of patients (pts) relapse and receive diverse chemotherapies (CT) producing modest benefits. The median PFS in relapse after platinum based CT is less than 4 months and median OS less than 1 year. New innovative strategies are urgently needed. Since CS showed high DNA damage response activity and potentially a high tumor mutation load resulting in neo-antigens, a synergy between PARPi and anti-PD1 is expected. Methods: ROCSAN is a multicentric, randomized, open-label, integrated Phase II/III study. In the Phase II, 63 pts with recurrent or progressing endometrial or ovarian CS after at least a first line of platinum-based CT will be randomized (2:2:1) to receive either niraparib in monotherapy, niraparib in combination with dostarlimab or standard CT (paclitaxel, doxorubicine, gemcitabine, topotecan). Stratification factors include the number of previous CT lines (1 vs 2-3), FIGO stage at diagnosis (I-II vs III-IV), CS localisation (ovarian vs endometrial), and performance status (0-1 vs 2). The primary objective of the Phase II is to select the best experimental strategy between niraparib and dostarlimab/niraparib combination based on Response Rate at 4 months (RR-4M by RECIST1.1). A single stage design with a 10% unacceptable RR-4M and a 30% targeted RR-4M was used to determine Phase II sample size, assuming a 10% one sided alpha for each comparison and more than 90% power. A pick-the-winner selection design could be used in case of promising efficacy in each experimental arm. At the interim analysis, an Independent Data Monitoring Committee will make recommendation for the selection of the optimal experimental arm. The Steering committee could then support to continue enrolment for the international Phase III which is calibrated to detect an improvement in median OS from 7 months (Standard CT) to 11.7 months (best experimental arm). Assuming a 5% alpha level and 80% power, 133 additional pts could be randomized (2:1). Secondary endpoints include safety, PFS, PFS2, TTST, ORR, duration of response, patient report outcomes (assessed via EORTC QLQ-C30 OV28, HADS, PRO-CTCAE). A translational program supported by European Community is associated to the clinical study to identify predictive biomarkers of response/resistance to study treatments, to correlate with immune environment, a special focus on genetic instability and the EMT process will be included. Trial is currently recruiting only in France for the phase II part, the first pt was randomized in July 2020. Clinical trial information: NCT 03651206.