ctDNA for Prognostication and Monitoring in Patients with Metastatic Endometrial Carcinoma Treated with Olaparib: Validation in the GINECO-UTOLA Trial

PURPOSE: ctDNA may offer a noninvasive means to evaluate tumor response and anticipate disease dynamics before radiologic changes in advanced endometrial carcinoma. EXPERIMENTAL DESIGN: This ancillary analysis included patients from the multicenter, randomized, phase II GINECO-UTerin OLAparib (UTOLA) trial (NCT03745950) evaluating olaparib/placebo as maintenance after first-line platinum-based chemotherapy. Plasma samples were collected at screening after chemotherapy (baseline), 3 months (M3), and progression. ctDNA detection was assessed by a validated methylation-based Droplet Digital PCR (MethddPCR) assay targeting DNA positions universally methylated in endometrial carcinoma. RESULTS: Among 130 evaluable patients, ctDNA was detected in 25 of 129 (19%, 1 technical fail) at baseline, 15 of 80 (19%) at M3, and 33 of 52 (63%) at progression. Baseline ctDNA positivity was independently associated with poorer progression-free survival (PFS) [median 1.81 vs. 7.39 months; adjusted HR = 5.33 (3.17-8.97)] and overall survival (OS) [10.3 vs. 24.7 months; adjusted HR = 3.98 (2.28-6.91); adjusted for age, stage IV at diagnosis, p53abn subgroup, and residual measurable lesions after chemotherapy]. Patients with baseline ctDNA had median OS of 9.36 months under olaparib versus 19.6 months under placebo (log-rank P = 0.05). Patients with increasing ctDNA at M3 had median PFS of 1.67 months, versus 9.64 months without, and median OS of 18.8 versus 25.8 months. ctDNA rising was predictive of poor postprogression OS under olaparib but not under placebo (interaction test, P < 0.001). CONCLUSIONS: MethddPCR-ctDNA is an independent prognostic biomarker for OS in advanced/metastatic endometrial carcinoma. MethddPCR-ctDNA may identify patients unlikely to benefit from PARP inhibition, guide therapeutic decisions, and should be further evaluated as a new stratification parameter in future endometrial carcinoma trials.