Long-term survival of early stage I epithelial ovarian cancer: A multicenter retrospective observational study (321)

Abstract

<b>Objectives:</b> Therapy for early-stage epithelial ovarian cancer (EOC) involves complete surgical staging with or without adjuvant chemotherapy. The current international multi-center study aimed to investigate the long-term survival of different histological subtypes for stage I EOC. <b>Methods:</b> A multi-center cohort study was performed among all patients with FIGO stage I (IA-IC3) EOC treated at four European referral centers between 1985 and 2021. Overall survival (OS) and progression-free (PFS) survival were compared between the different stage I groups using Kaplan-Meier survival curves. <b>Results:</b> A total of 1115 patients met the inclusion criteria. Of them, 48.4% (<i>n</i>=540) were in stage IA, 6.6% (<i>n</i>=73) stage IB, and 45% (<i>n</i>=502) stage IC: stage IC1 54% (<i>n</i>=271), stage IC2 31.5% (<i>n</i>=158), and stage IC3 14.5% (<i>n</i>=73). The predominant histologic subtypes included highgrade serous (25.4%), low-grade endometrioid (24.8%), and clear cell (19%). Complete surgical staging, including lymphadenectomy, was performed in 62.1%, and 60% received adjuvant platinum-based chemotherapy. The median follow-up was 48 months. The median five-year (5y) OS and PFS rates were 94% and 86%, respectively, with no difference between stage IA and IB. However, a significantly better OS and PFS were observed for stage IA as compared to stage IC (p=0.007 and p<0.001, respectively). Considering histologic subtypes, a significant better PFS was documented for low-grade mucinous and low-grade endometrioid subgroup (HR: 0.22; 95% CI: 0.09-0.45, p=0.001; HR: 0.49; 95% CI: 0.29-0.83, p=0.007, respectively), as well a better OS for the latter (HR: 0.43; 95% CI: 0.22-0.86, p=0.017). In stage IA-B, the different histology subtypes showed a comparable prognosis (5y: OS: 96% and PFS: 92%), with the exception of a worsened OS for high-grade mucinous cases (HR: 5.90; 95% CI: 1.55-22.4, p=0.009). Among stage IC, the histologic subgroups showed comparable OS (5y 92%), but significantly better PFS for low-grade mucinous and low-grade endometrioid subtypes (HR: 0.21; 95% CI: 0.05-0.86, p=0.031; HR: 0.44; 95% CI: 0.23-0.84, p=0.013, respectively). In the subgroup of high-grade serous ovarian cancer patients in stage IC disease, the chemotherapy with carboplatin/paclitaxel seems to be superior compared to single-agent platinum (5y OS: 100% vs 83%; p=0.009). In multivariate analysis, partial staging procedure (compared to complete) was found as risk factor for worsen PFS (HR: 1.73; 95% CI: 1.13-2.66, p=0.012), while low-grade endometrioid histology (compared to high-grade serous) showed better outcome regarding OS (HR: 0.46; 95% CI: 0.22-0.95, p=0.036) and PFS (HR: 0.42; 95% CI: 0.25-0.73, p=0.002). <b>Conclusions:</b> Overall, stage I ovarian cancer patients treated in referral centers exhibited an excellent prognosis regardless of the histologic type. Histologic subtype and quality of surgical treatment affect the prognosis. Our data suggest platinum-based combination chemotherapy for the subgroup of FIGO stage IC high-grade serous ovarian cancer.