Adjuvant Therapy and Molecular Diagnostics in Noninvasive Uterine Serous Carcinoma [ID 1097]

INTRODUCTION: Uterine serous carcinoma (USC) is a rare but aggressive subtype of endometrial cancer that portends a high risk of recurrence and low overall survival. Systemic therapy is recommended for patients with myoinvasive or advanced-stage disease; however, there is limited data to guide adjuvant therapy in non-myoinvasive disease. This study aims to identify treatment patterns and pathologic characteristics that are associated with survival in non-myoinvasive USC. METHODS: Patients with stage IA non-myoinvasive USC diagnosed at our institution from 2002 to 2023 were included. Demographics, medical history, pathology, and treatment information were summarized. Overall survival (OS) and progression-free survival (PFS) were estimated using Kaplan–Meier plots. Cox proportional hazard models were used to evaluate the effect of patient variables on OS and PFS. RESULTS: Sixty-four patients met inclusion criteria. Eleven patients (18.6%) identified as non-White. Forty-six patients (80.7%) received adjuvant treatment. Eleven patients recurred, with a 5-year cumulative incidence of recurrence of 18.3%. Of those who recurred, nine (81.8%) had undergone adjuvant treatment, with six (54.5%) having received adjuvant chemotherapy. Adjuvant chemotherapy was associated with improved OS (hazard ratio 0.26; 95% CI, 0.08–0.87; P =.028). CONCLUSIONS/IMPLICATIONS: National Comprehensive Cancer Network guidelines allow observation, brachytherapy, or systemic chemotherapy after surgical staging for noninvasive USC. In this relatively large cohort of exclusively noninvasive USC cases, recurrence rates were high despite high rates of adjuvant treatment. Although chemotherapy was associated with an improvement in OS, it did not eliminate the risk of recurrence. Further molecular testing is underway for this cohort to better identify prognostic biomarkers.