Clinicopathological characterization of a real-world multicenter cohort of endometrioid ovarian carcinoma: Analysis of the French national ESME-Unicancer database.

BACKGROUND: Prognostic significance of endometrioid epithelial ovarian cancer (EOC) is controversial. We compared clinical, pathological, and biological features of patients with endometrioid and serous EOC, and assessed the independent effect of histology on outcomes. METHODS: We conducted a multicenter retrospective analysis of patients with EOC selected from the French Epidemiological Strategy and Medical Economics OC database between 2011 and 2016. Our main objective was to compare overall survival (OS) in endometrioid and serous tumors of all grades. Our second objectives were progression-free survival (PFS) and prognostic features. RESULTS: Out of 10,263 patients included, 3180 cases with a confirmed diagnosis of serous (N = 2854) or endometrioid (N = 326) EOC were selected. Patients with endometrioid histology were younger, more often diagnosed at an early stage, with lower-grade tumors, more frequently dMMR/MSI-high, and presented more personal/familial histories of Lynch syndrome-associated cancers. BRCA1/2 mutations were more frequently identified in the serous population. Endometrioid patients were less likely to receive chemotherapy, with less bevacizumab. After median follow-up of 51.7 months (95CI[50.1-53.6]), five-year OS rate was 81% (95CI[74-85]) in the endometrioid subgroup vs. 55% (95CI[53-57] in the serous subset (p < 0.001, log-rank test). In multivariate analyses including [age, ECOG-PS, FIGO, grade, and histology], the endometrioid subtype was independently associated with better OS (HR = 0.38, 95CI[0.20-0.70], p= 0.002) and PFS (HR = 0.53, 95CI[0.37-0.75], p < 0.001). CONCLUSIONS: Clinicopathological features at diagnosis are not the same for endometrioid and serous EOC. Endometrioid histology is an independent prognosis factor in EOC. These observations suggest the endometrioid population requires dedicated clinical trials and management.