Should stage IIIC ovarian cancer be further stratified by intraperitoneal vs. retroperitoneal only disease? A Gynecologic Oncology Group study

Objective: To examine whether clinical outcomes varied with intraperitoneal (IP) and/or retroperitoneal (RP) involvement in stage IIIC epithelial ovarian cancer (EOC) patients with microscopic residual disease after cytoreduction. Methods: Retrospective review was performed for EOC patients enrolled in Gynecologic Oncology Group (GOG)-182 who underwent primary cytoreduction to microscopic residual disease. Patients were divided into 3 groups: stage IIIC by lymphadenopathy with < 2 cm IP spread (RP); > 2 cm IP spread and negative nodes (IP/RP-); and > 2 cm IP dissemination and positive lymphadenopathy (IP/RP+). Product-limit and multivariate proportional hazards modeling were used. Results: Analyses included 417 stage IIIC women who underwent primary cytoreduction with lymphadenectomy to microscopic residual. There were 203, 123, and 91 in the RP, IP/RP-, and IP/RP+ groups, respectively. IP/RP+ and IP/RP- were associated with worse progression-free survival (PFS) (Hazard Ratio (HR) 1.68, 95% confidence interval (CI) 1.23-2.30; HR 1.38, 95% CI 1.04-1.84) vs. RP only. IP/RP+ was associated with worse overall survival (OS) (HR 1.79, 95% CI 1.24-2.57) while IP/RP- trended towards worse OS (HR 1.21, 95% CI 0.85-1.73) vs. RP only. Median PFS for IP/RP+ and IP/RP- groups was 21 and 29 months, respectively, vs. 48 months in the RP group (p = 0.0007) and median OS of 63 and 79 months vs. "not reached," respectively (p = 0.0038). Conclusions: Among EOC patients surgically cytoreduced to microscopic residual disease, those upstaged to IIIC by retroperitoneal involvement demonstrated significant improvement in PFS and OS compared to patients with intraperitoneal tumor, suggesting that these women may represent a unique subset of FIGO stage IIIC patients.