Prognostic significance of positive peritoneal cytology in early-stage endometrial carcinoma after postoperative radiotherapy: a single-center retrospective cohort study

The prognostic significance of positive peritoneal cytology (PPC) in early-stage endometrial carcinoma (EC) remains controversial, particularly in the setting of contemporary adjuvant treatment. We aimed to evaluate the association of PPC with survival outcomes and recurrence patterns in patients with early-stage EC. This retrospective single-center cohort study included 463 patients with FIGO 2009 stage I-II EC who underwent primary surgical staging between 2015 and 2020. Patients were stratified into PPC (n = 47) and negative peritoneal cytology (NPC, n = 416) groups. Disease-free survival (DFS) and recurrence patterns were assessed using Kaplan–Meier methods and Cox proportional hazards regression models. Multivariable Cox regression was prespecified as the primary analysis, and inverse probability of treatment weighting (IPTW)-based Cox regression was performed as a sensitivity analysis. The cohort predominantly comprised FIGO 2009 stage I disease (93.7%) and low-grade endometrioid carcinomas. Over a median follow-up of 54.4 months, patients with PPC were more likely to receive intensified adjuvant treatment than those with NPC. In the primary multivariable Cox model adjusted for age, histology, lymphovascular space invasion, and FIGO 2009 stage, PPC was independently associated with worse DFS (HR, 2.08; 95% CI, 1.01–4.28). In an interaction model, the association between PPC and DFS appeared to vary across adjuvant treatment categories, although subgroup-specific estimates were imprecise because of limited events and wide confidence intervals. In IPTW-based sensitivity analyses, this adverse association was attenuated and no longer statistically significant. PPC was also associated with a higher frequency of abdominal and distant recurrences. PPC was associated with worse DFS in early-stage EC in the primary multivariable analysis. Although this association was attenuated in IPTW-based sensitivity analyses, peritoneal cytology may still provide prognostic information, and further validation in larger, molecularly characterized cohorts is warranted.