Malignant peritoneal cytology and increased mortality risk in stage I non-endometrioid endometrial cancer

Objective. To examine the survival of women with stage I non-endometrioid endometrial cancer with malignant peritoneal cytology. Methods. A retrospective observational cohort study was conducted to examine the National Cancer Institute's Surveillance, Epidemiology, and End Results Program from 2010 to 2016. Women with stage I serous, clear cell, carcinosarcoma, undifferentiated, and mixed endometrial cancer with known peritoneal cytology results at hysterectomy were examined (N= 4506). Propensity score inverse probability of treatment weighting was used to balance the measured covariates, and survival outcomes were assessed according to peritoneal cytology results. Results. Malignant peritoneal cytology was reported in 401 (8.9%) women. In multivariable analysis, older age, serous histology, and large tumors were associated with an increased likelihood of malignant peritoneal cytology (all, P< 0.05). In a propensity score weighted model, malignant peritoneal cytology was associated with a nearly two-fold increase in all-cause mortality risk compared to negative peritoneal cytology (5-year rates, 63.4% versus 80.2%, hazard ratio 2.18, 95% confidence interval 1.78-2.66). In sensitivity analyses, malignant peritoneal cytology was associated with decreased overall survival in old and young age groups, serous, clear cell, carcinosarcoma, and mixed histology groups, stage T1a disease, and staged and unstaged cases, but not for stage T1b disease. Difference in 5-year overall survival rates between the malignant and negative peritoneal cytology groups was particularly large among those with clear cell histology (24.0%), stage T1a disease (19.4%), aged >78 years (182%), and serous tumors (17.6%). Conclusion. Malignant peritoneal cytology can be prevalent in stage I non-endometrioid endometrial cancer. Our study suggests that malignant peritoneal cytology is a prognostic factor for decreased survival in stage I nonendometrioid endometrial cancer. (C) 2020 Elsevier Inc. All rights reserved.