A feasibility study of postoperative chemotherapy with S-1 and cisplatin (CDDP) for stage III/IV gastric cancer (CCOG 1106).

BACKGROUND

The standard of care for stage II/III gastric cancer in Japan is D2 dissection followed by adjuvant S-1 monotherapy. Outcome of patients with stage III disease remains unsatisfactory, calling for a more intensive adjuvant chemotherapy regimen, for which evidence in advanced/metastatic cancer research suggests S-1/cisplatin (CDDP) as a candidate. Although S-1/CDDP was poorly tolerated postoperatively in the previous trial, compliance was dramatically improved by insertion of one cycle of S-1 monotherapy, which delayed administration of CDDP by 6 weeks.

METHODS

A feasibility study of post-gastrectomy S-1/CDDP was performed. Patients with stage III/IV gastric cancer were eligible. The first cycle of chemotherapy consisted of S-1 monotherapy, and intensive antiemetic drugs were prescribed when patients were administered CDDP. The primary endpoint was the completion rate of four cycles of S-1/CDDP. The secondary endpoints were the relative dose intensity, safety, progression-free survival time and overall survival time. Several criteria to skip, postpone or reduce the dose had been predetermined.

RESULTS

Between 2010 and 2011, 33 patients were enrolled. Four patients had stage IIIA disease, 7 patients had stage IIIB disease, 11 patients had stage IIIC disease, and 11 patients had stage IV disease. The completion rate of the protocol treatment was 60.6%. The relative dose intensity of S-1 was 77.3% and that of CDDP was 72.3%.

CONCLUSIONS

The protocol-specified delay in the administration of CDDP dramatically improved the relative drug intensity in the postoperative adjuvant setting, although the completion rate did not reach the expected level.