Malignant Peritoneal Cytology Predicts Poor Prognosis and Differential Adjuvant Therapy Benefit in Endometrioid Endometrial Carcinoma: A SEER-Based Propensity Score-Matched Analysis

The prognostic significance of malignant peritoneal cytology (PC) in endometrioid endometrial carcinoma (EC) and its clinical implications for adjuvant therapy selection remain controversial. This retrospective cohort study analyzed 9631 endometrioid EC patients from Surveillance, Epidemiology, and End Results (SEER) Program data (2010-2017). Prognostic determinants of overall survival (OS) were identified through Cox regression. Propensity score matching (PSM) generated balanced cohorts: 826 malignant PC, 148 atypical/suspicious PC, and 974 negative PC cases. Survival distributions were compared using Kaplan-Meier analysis. Univariable analysis identified significant OS associations with age, histopathological grade, tumor stage, and PC status (all p < 0.05). Multivariable analysis confirmed malignant PC as an independent prognostic factor. Post-PSM: Malignant PC subgroup showed significantly reduced OS vs others (p < 0.001). Stage-specific effects in malignant PC subgroup: Radiation improved OS only in regional disease (p = 0.016). Systemic therapy reduced OS in all-stage malignant PC (p = 0.022). Atypical/suspicious PC subgroup: No survival benefit from radiation (p = 0.71) or systemic therapy (p = 0.38). Malignant PC independently predicts poor prognosis in endometrioid EC but requires cautious interpretation in therapeutic decision-making due to its differential adjuvant therapy effects. PC status alone cannot guide risk stratification; treatment decisions should integrate stage-specific efficacy data. Prospective validation is imperative.