Introduction Previous studies have demonstrated an overall survival benefit with intraperitoneal chemotherapy in Stage III pelvic high-grade serous carcinoma (HGSC), but no studies have evaluated this treatment in early stage disease. We offered IP chemotherapy (IP/IV) to patients with Stage I-II HGSC from 2009–2022. The objectives are to evaluate time to recurrence (TTR), progression-free survival (PFS), and overall survival (OS) associated with IP/IV compared to standard intravenous (IV) chemotherapy.

Methods This is a retrospective population-based cohort study of patients with stage I-II pelvic HGSC, who underwent primary surgery and adjuvant chemotherapy between 2009–2022. Statistical Analysis included Pearson’s Chi-square, Kaplan-Meier survival analysis, and Cox regression model to adjust for covariates.

Results 77 and 60 patients received IP/IV and IV chemotherapy, respectively. Those who received IP/IV were significantly younger. Stage distribution was similar between treatment groups. There were 24.7% and 5% confirmed BRCA mutation carriers, but 13% and 26.7% with unknown BRCA status in the IP/IV and IV groups, respectively. Five-year kaplan-meier outcomes were 77.7% vs. 67.7% TTR (p=0.49), 77.7% vs. 64.9% PFS (p=0.44), and 93.4% vs. 85.1% OS (p=0.29) in the IP/IV and IV groups, respectively. In multivariate analysis, IV chemotherapy trended towards shorter TTR, and worse PFS and OS. Those with unknown BRCA status had significantly better outcomes than confirmed BRCA negative (see tables 1 and 2).

Conclusion/Implications There are improved outcomes for patients with early stage HGSC who received IP/IV chemotherapy, although not statistically significant. The unknown BRCA status group could have unrecognized BRCA mutation carriers, possibly accounting for better outcomes than those without BRCA mutations.