Value of combined adjuvant chemotherapy and radiation on survival for stage III uterine cancer: is less radiation equal to more?

OBJECTIVE: Locally advanced endometrioid adenocarcinoma (LA-EAC) accounts for the majority of deaths for this cancer, yet there is no consensus on adjuvant treatment after surgery. Past studies suggest that combined modality treatment (CMT) may improve outcomes over treatment with chemotherapy (CT) or radiation therapy (RT, either external beam radiotherapy [EBRT] or vaginal brachytherapy [VBT]) alone. Using a large US-based population-based registry, we evaluated adjuvant CMT in LA-EAC and the relative benefit of regional EBRT compared to focused VBT. METHODS: We studied patients diagnosed with Stage III LA-EAC between 2004 and 2013 from the National Cancer Data Base (NCDB). We used Cox regression and a log-rank test to assess survival based on treatment with CT alone, EBRT alone, VBT alone, or CMT with EBRT and/or VBT. We used a χ(2) test to compare covariates between patients receiving CMT with EBRT or VBT. RESULTS: Patients who received CMT had better survival than those who received CT or EBRT/VBT alone. Compared to CMT with VBT, patients who received CMT with EBRT were slightly older and had more advanced-stage or positive nodes, and fewer had lymph node surgery. We found no survival difference between CMT with EBRT and CMT with VBT even when categorizing patients as high or low risk according to age, grade, and stage (low-risk p=0.3460; high-risk p=0.2158). CONCLUSION: CMT was associated with superior survival outcomes compared to monotherapy. We observed no survival difference between radiation modalities in CMT, which highlights the effectiveness of a more focused treatment like brachytherapy.