Outcomes of Adjuvant Therapy for Stage IA Serous Endometrial Cancer

Purpose: Serous adenocarcinoma is a rare, aggressive histologic subtype of endometrial cancer with a high rate of recurrence and a poor prognosis. The optimal adjuvant treatment for early-stage patients is unclear. Our objective was to evaluate the outcomes of stage IA serous endometrial cancers only treated at a single institution and determine whether our current approach of chemotherapy plus vaginal brachytherapy (VBT) is sufficient. Methods: A retrospective chart review of our institution's pathology database, including all cases of stage IA serous endometrial carcinoma from 2000-2014 was completed. Kaplan-Meier estimates were calculated for Overall and Recurrence-Free Survival (OS and RFS); hazard ratios were calculated using Cox proportional hazards modeling for independent prognostic factors. Results: There were 63 patients with stage IA serous endometrial cancer of whom 79.4% were surgically staged. Percent RFS was 76.5% at five years while OS was 84.7% for the whole cohort. One of the 23 patients receiving VBT and chemotherapy recurred at the vagina versus four of 32 patients who were observed. Two patients in the observation group recurred in the pelvis while there were no first pelvic recurrences in the VBT and chemotherapy group (non- significant). Overall survival was 95% in the brachytherapy and chemotherapy group versus 79.6% in the observation group (non-significant). Post-operative management included observation (n=33), combination VBT and chemotherapy (n=21), or chemotherapy with or without external beam radiation therapy (EBRT) (n=9). Discussion: We report one of the largest cohorts of serous endometrial cancer stage IA patients. Our results emphasize the inferior RFS and OS of stage IA serous versus endometrioid endometrial cancer patients. While some centers continue to use EBRT for these patients, our results demonstrate low pelvic recurrence rates with radiotherapy limited to VBT, as well as the high systemic risk regardless of treatment. We advocate for combination chemotherapy and brachytherapy given the poor outcomes in these patients.