Clear cell carcinoma of the endometrium: Evaluation of prognostic parameters in a multi-institutional cohort of 165 cases

Objectives: Clear cell carcinoma (CCC) comprises a rare yet an aggressive subtype, accounting for less than 5% of all uterine carcinomas. Several clinicopathologic features have been predictive of poor prognosis; however, data remain controversial. The aim of this study was to evaluate the clinicopathologic features of a multi-institutional cohort of endometrial CCC in order to identify which, if any, have prognostic significance. Methods: Retrospective review of endometrial CCC diagnosed between 1995 and 2012 at 3 institutions was conducted to evaluate clinicopathologic parameters: age, race, tumor size, stage, myometrial invasion (MI), lymphovascular invasion, lymph node and adnexal involvement, adjuvant therapy, and outcomes. Data were analyzed using Fisher exact, Cox regression, and Kaplan-Meier analyses. Results: Patients' ages ranged from 36 to 90 years (median, 67 years).The median tumor size was 3.6 cm. Inner-half MI was present in 44%, lymphovascular invasion in 34%, adnexal involvement in 16%, and lymph node metastasis in 30% of cases. Fifty-eight percent of the patients presented with early-stage disease. The 5-year overall survival (OS)was 58%. Shorter disease-free interval (DFI)was significantly associatedwith older age at diagnosis (970 years), advanced-stage disease, adnexal involvement, and deep MI (P = 0.005, P = 0.001, P = 0.001, and P = 0.003, respectively). Patientswho received adjuvant chemotherapy had a significantly worseDFI and 5-yearOS (P= 0.001 and P= 0.001, respectively). Asignificantly shorter 5-year OS was noted with advanced stage (IIIYIV) and presence of adnexal involvement (P = 0.001 and P = 0.021, respectively). On Cox regression analysis, advanced-stage disease, older age, and adnexal involvement were significant independent predictors of worse DFI (P = 0.001, P = 0.005, and P = 0.019, respectively), whereas inner-half MI was a significant independent predictor of longerDFI (P= 0.004).Adjuvant radiotherapy alonewas a significant independent predictor of better 5-year OS (P = 0.012). Conclusions: In our series of endometrial CCC, older age at diagnosis, advanced stage, deep MI, and adnexal involvement were independent poor prognostic factors. Adjuvant radiotherapy had a significant positive impact on 5-year OS.