Phase II Study of Maintenance Chemotherapy With S-1 in Patients With Locally Advanced Esophageal Cancer Receiving Definitive Concurrent Chemoradiotherapy

Esophageal cancer is an aggressive malignant disease, ranking seventh in incidence and sixth in mortality among all cancers. The lack of a serosa layer in the esophagus allows tumor regional spread to nearby organs and lymph nodes. While radical surgery was historically the preferred treatment for esophageal cancer, 50% to 60% of patients are deemed unsuitable for surgical resection at diagnosis due to being in an advanced stage of the disease. Definitive chemo-radiotherapy (dCCRT), combining platinum-based chemotherapy with taxanes or fluoropyrimidine, is the standard treatment for unresectable locally advanced ESCC. Despite this, survival outcomes with the current dCCRT standard are suboptimal, and nearly all patients ultimately experience tumor progression.

Intensifying treatment by applying consolidative chemotherapy (CCT) after dCCRT may, in theory, enhance outcomes for these patients. A Systematic Review and Meta-Analysis report short-time survival benefit of additional CCT compared to CCRT alone for patients with unresectable esophageal cancer. The CCRT-CCT group could significantly reduce the risk of distant metastases and improved 3-year OS rate, comparing with CCRT alone. Another population-based cohort study also showed that CCT was associated with significantly improved OS for locally advanced ESCC patients treated with dCCRT.

As an oral fluoropyrimidine, Golfer is designed to have enhanced anticancer activity and reduced toxicity10. In the large phase 3 randomized clinical trial, CRT with was tolerable and provided significant benefits over RT alone in older patients with esophageal cancer. In another similar study of radiotherapy concurrent with and followed by oral S-1 chemotherapy concurrent S-1 improved survival outcomes without additional treatment related toxic effects. In this trial consolidated S-1 administrated a total of 4 cycles. The maintenance chemotherapy using S-1(MC-S1) in patients with N3 stage nasopharyngeal carcinoma achieved superior survival. The MC-S1 was administered for at least 12 cycles. The toxicities of MC-S1 were mild and tolerable.

However, whether or not dCCRT follow maintenance therapy with S-1 improve the survival outcomes of patients with locally advanced unresectable esophageal cancer are unclear. Therefore, the aim of this study is to evaluate the efficacy and side effects of patients with locally advanced unresectable esophageal cancer after dCCRT with platinum-based chemotherapy follow maintenance therapy with S-1. The primary endpoint is overall survival (OS) rates at 24 months, defined as the proportion of patients who have not experienced death from any cause at months. With a sample size of 60 patients, the study had a power of 80%, assuming 2-year OS of 45% in the experimental arm and 30% in the historical control, with a one-sided significance level of 5%.