261 The impact of histology and adjuvant therapy on survival and recurrence patterns among high-grade endometrial cancer with retroperitoneal metastases. (13th November 2020) - McEachron, J
Abstract : Objectives: To evaluate the difference in recurrence patterns and survival among stage IIIC high-grade endometrial cancer (HGEC) treated with surgery followed by adjuvant chemotherapy, radiation (RT) or both (chemoradiation). Methods: A multicenter retrospective analysis of surgically-staged IIIC HGEC was conducted from 2000 to 2018, including grade-3 endometrioid (G3), serous, clear cell (CC) and carcinosarcoma. Differences in the frequency of recurrence sites and treatment delays were identified using Pearson's χ2-test. PFS and OS were calculated using Kaplan-Meier estimates. Results: A total of 155 patients were evaluable; 41.9% carcinosarcoma, 36.8% serous, 17.4% G3 and 3.9% CC; 67.1% received chemoradiation, 25.8% received chemotherapy-alone and 7.1% received RT-alone. Adjuvant therapy regimens were well-balanced between different histologies (p=0.351). There was no difference in the frequency of treatment delays between regimens (p=0.571). G3 tumors recurred less frequently (66.7%) versus serous (80.7%), CC (83.3%) and carcinosarcoma (84.6%)(p=0.269). Abdominal recurrence occurred most often in CC and serous. Carcinosarcoma was most likely to recur in the lung. There was a trend towards greater retroperitoneal recurrence with chemotherapy-alone (25.9%) versus chemoradiation (8.4%) and RT-alone (7.7%)(p=0.252). G3 tumors demonstrated improved PFS and OS (26 and 42-months, respectively) versus serous (17 and 30-months, respectively), carcinosarcoma (14 and 24-months, respectively) and CC (24 and 30-months respectively)(p=0.002, p<0.001). Chemoradiation was superior to chemotherapy-alone and RT-alone in PFS (p<0.001) and OS (p<0.001). Conclusion: The majority of stage IIIC HGEC recurs. Chemoradiation was associated with improved survival and less retroperitoneal recurrence versus chemotherapy-alone. G3 tumors demonstrated improved survival compared other histologies regardless of adjuvant treatment modality.