Prognosis and treatment of positive peritoneal cytology in early endometrial cancer: matched cohort analyses from the National Cancer Database

BACKGROUND: While positive peritoneal cytology is no longer included among the endometrial cancer staging criteria, Federation International de Gynecologie et Obstetrique recommends continued collection of pelvic washings for cytology to produce additional data that may be used to determine the significance of positive cytology for prognosis and treatment of endometrial cancer. OBJECTIVES: The objectives of the study was to validate that positive cytology is a predictor of decreased survival in early endometrial cancer and to test whether adjuvant chemotherapy for positive cytology is associated with increased survival. STUDY DESIGN: We performed an observational retrospective cohort analysis of the 2010-2013 National Cancer Database including women with cytology status and Federation International de Gynecologie et Obstetrique stage IA-II endometrial cancer. Overall cohort and matched cohort survival analyses were performed with and without imputation of missing data. We also performed survival analyses of women with positive cytology grouped by chemotherapy exposure. Multivariable Cox proportional-hazards regressions were performed to adjust for possible confounders. A variety of sensitivity analyses, including robustness of results to possible unmeasured confounding, were reported. RESULTS: A total of 16,851 women including 953 with positive cytology were included. Four-year overall survival was 79.5% (range, 76.2-83.0%) for women with stage I/II with positive cytology vs 92.2% (range, 91.5-92.9%), 83.3% (range, 81.6-84.9%), and 86.8% (range, 85.1-88.5%) for stage IA, IB, and II with negative cytology, respectively (P <= .001). Positive cytology was associated with decreased survival (hazard ratio [95% confidence interval], 1.85 [range, 1.54-2.21], P < .001). For women with Federation International de Gynecologie et Obstetrique grade 1/2 endometrioid adenocarcinoma, the hazard of death associated with positive cytology was similar (hazard ratio [95% confidence interval], 1.85 [1.28-2.67], P<.001). Use of adjuvant chemotherapy by women with positive cytology was associated with increased survival (hazard ratio [95% confidence interval], 0.62 [0.40-0.95], P = .03). CONCLUSION: Positive peritoneal cytology was associated with decreased overall survival of women with Federation International de Gynecologie et Obstetrique stage I/II endometrial cancer, including low-grade endometrioid endometrial cancer. Treatment of women with stage I/II endometrial cancer and positive cytology with adjuvant chemotherapy was associated with increased survival.