A pilot study for preoperative concurrent chemoradiotherapy with S-1 and cisplatin for locally advanced gastric cancer.

This study aims to determine the feasibility and effectiveness of concurrent chemoradiotherapy with the combination of S-1 and cisplatin in locally advanced gastric cancer. Treatment-naive patients with locally advanced gastric cancer were enrolled. The patients received concurrent radiation (a total dose of 45 Gy: 25 fractions of 1.8 Gy) and chemotherapy. S-1 was given orally at 60 mg/mg² bid for 21 consecutive days with a resting period of 7 days. Cisplatin was given intravenously at 70 mg/m² for 2 hours on day 1. The tumor response was evaluated 4-5 weeks after the completion of radiotherapy, and surgical resection was tried with curative intent if possible. Nine patients were enrolled, and all patients completed the initially planned concurrent chemoradiotherapy. Clinical response rate was 88.9% (8/9). Seven (77.8%) out of 9 patients underwent surgery, and an R0 resection was achieved in all of them. Pathological assessment of tumor regression after preoperative chemoradiotherapy showed total regression in 1 patient (14.3%), near total regression in 2 (28.6%), moderate regression in 3 (42.9%), and minimal regression in 1 (14.3%). Grade III/IV toxicity included anemia (44.4%), neutropenia (33.3%), and thrombocytopenia (22.2%). Preoperative concurrent chemoradiotherapy with S-1 and cisplatin is feasible and safe, and could offer an improved chance of tumor regression and curative resection in patients with locally advanced gastric cancer. Further trials with larger numbers of patients are warranted.