288. ASSOCIATION BETWEEN ENDOGENOUS SUBTYPE CLASSIFICATION FOR ESOPHAGEAL SQUAMOUS CELL CARCINOMA AND OUTCOME OF CHEMORADIOTHERAPY

Abstract Chemoradiotherapy (CRT) is a treatment option for esophageal squamous cell carcinoma (ESCC) and prognosis of patients achieved complete response is good. However, we cannot predict the outcome of the CRT before treatment. In previous single center study, RNA expression analysis using biopsy samples of 274 ESCC patients before CRT identified endogenous subtype classification. E type (high expression of squamous epithelial markers) showed good prognosis and M2 type (high expression of mesenchymal markers) did poor prognosis. We conducted a prospective multicenter study to confirm the association between molecular subtyping and outcome of CRT. From January 2015 to July 2016, we prospectively recruited 226 patients from 10 hospitals in Japan. This study was approved by the institutional review board at each hospital, and we obtained written informed consent from all patients (UMIN000016141). Biopsy samples were obtained before treatment, and molecular subtyping was performed. Treatment was selected by each physician. Clinical outcome of the patients treated by CRT was investigated according to the molecular subtype. Among 226 patients, two patients withdrew the content. We could identify the subtype classification in all 224 patients. Fifty-seven patients (25.4%) were classified to E type and 56 (25.0%) to M2 type. In 224 patients, 97 received treatment include CRT (77: CRT alone, 16: induction chemotherapy followed by CRT, 4: CRT followed by surgery). The proportion of patients alive at 5 years was 48.8% (95% CI 28.0-66.7%) in E type, and 29.8% (95% CI 12.4-49.6%) in M2 type. The patients in E type showed better prognosis although it was not significant statistically (HR 0.5; 95% CI 0.23-1.09; p = 0.08). This prospective multicenter study could show the usefulness of molecular subtyping of ESCC to predict the outcome of CRT.