Benefit of combination chemotherapy and radiation stratified by grade of stage IIIC endometrial cancer

Objective The optimal strategy for adjuvant therapy in stage IIIC endometrial cancer has not been determined. Our aim was to evaluate survival benefit of different treatments and to investigate if benefit varied by histologic grade. Methods We identified 199 patients with stage IIIC endometrial cancer from 2000 to 2012 through the Siteman Cancer Center registry. All patients underwent surgical staging followed by no adjuvant therapy (NAT), radiation (RT), chemotherapy (CT) or chemoradiation (CRT). The association between adjuvant treatment and overall survival was explored using Kaplan-Meier plots and multivariable Cox regression analysis. Multivariable analysis was stratified by low- or high-grade to explore the interaction between grade and treatment. Results Most patients received CRT (50.3%) followed by CT (23.1%), RT (16.1%) and NAT (10.5%). Survival after CRT was superior to NAT (p < 0.001), RT (p = 0.010) and CT (p < 0.001). After adjusting for covariates, treatment with RT, CT and CRT led to a 57% (p = 0.024), 62% (p = 0.003) and 83% (p < 0.001) reduction in risk of death compared to NAT, respectively. With CRT as the reference, the adjusted hazard of death was higher with NAT (5.94, p < 0.001), RT (2.56, p = 0.009) and CT (2.24, p = 0.004). Stratifying by grade, RT and CRT led to a 67% (p = 0.039) and 85% (p < 0.001) reduction in death, compared to NAT in low-grade patients. CT and CRT led to a 72% (p = 0.003) and 83% (p < 0.001) reduction in death, compared to NAT in high-grade patients. Conclusions Our findings suggest that CRT should be the preferred adjuvant treatment strategy for patients with stage IIIC endometrial cancer.