Inter-institutional survival heterogeneity in chemoradiation therapy for esophageal cancer: exploratory analysis of the JCOG0303 study.

It is important to examine variation in the treatment effects of patients with esophageal cancer in order to generalize treatment outcomes. We aimed to investigate the range of prognostic differences among hospitals in the treatment of locally advanced esophageal cancer. The JCOG0303 study compared the efficacy of radiotherapy plus low-dose cisplatin and 5-fluorouracil with that of high-dose cisplatin and 5-fluorouracil for unresectable esophageal cancer. Of 32 institutions participating in the JCOG0303 study, the 18 institutions that enrolled three or more patients were included in this study. We predicted the 1-year survival in each institution by using a mixed-effect model. We found that the predicted 1-year survival in the 18 institutions with three or more patients was a median of 60.9%, with a range of 60.9-60.9%. This study is the first to investigated heterogeneity of survival in patients who received definitive chemoradiotherapy for locally advanced esophageal squamous cell carcinoma.