Phase II trial of S-1 for neoadjuvant chemotherapy against scirrhous gastric cancer (JCOG 0002)

The prognosis of scirrhous gastric cancer remains poor despite extended surgery or adjuvant or neoadjuvant chemotherapy. A pilot study of S-1 (TS-1; Taiho Pharmaceutical, Tokyo, Japan), an oral 5-fluorouracil derivative, for neoadjuvant chemotherapy unexpectedly showed good response and a promising effect on survival. Therefore, the Japan Clinical Oncology Group conducted a phase II trial to confirm the efficacy of S-1 for neoadjuvant chemotherapy against resectable scirrhous gastric cancer. Patients were eligible if they had typical scirrhous gastric cancer invading more than half of the stomach, and resectable disease confirmed by laparoscopic staging. The treatment schedule consisted of two courses (each, 4-week administration and 2-week withdrawal) of S-1 (100-120 mg/body per day), followed by radical surgery. Fifty-five eligible patients were registered. Three completed only one course of the neoadjuvant chemotherapy, whereas 52 completed two courses. Toxicity was acceptable, with a few grade 3 (5.5%) events, but no grade 4 adverse events. The response rate was 32.6% in 43 evaluable patients. Of the 55 patients, 2 refused operation, 1 developed lung metastasis, and 52 underwent laparotomy. The curative resection rate was 80.8%, with acceptable morbidity and no mortality. The survival curve at 2 years' follow up showed a better survival rate than that of the historical controls, but did not reach the expected survival rate. S-1 neoadjuvant chemotherapy appeared feasible and showed positive effects against scirrhous gastric cancer; however, the survival rate with S-1 did not reach the expected rate required when selecting an agent for a phase III trial to confirm the effectiveness of neoadjuvant chemotherapy against scirrhous gastric cancer.