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.