Effect of S-1 Adjuvant Chemotherapy on Survival following Recurrence and Efficacy of First-Line Treatment in Recurrent Gastric Cancer

BACKGROUND: As S-1 monotherapy has recently become the standard adjuvant regimen for stage II-III gastric cancer patients after curative gastrectomy in Japan, the question whether adjuvant S-1 affects the subsequent clinical course of relapsed patients has attracted great concern. PATIENTS AND METHODS: We retrospectively evaluated the effect of adjuvant S-1 on survival following recurrence and efficacy of first-line treatment in patients with recurrent gastric cancer after curative gastrectomy. A total of 89 patients were evaluated. Thirty patients received adjuvant S-1 (cohort A), 10 patients were given adjuvant chemotherapy with other oral 5-FU agents (cohort B) and 49 patients received no adjuvant chemotherapy (cohort C). RESULTS: Median survival time following recurrence was 287 days in cohort A, 451 days in B and 547 days in C, with a significant difference between A and C (p = 0.0034). Response rates of the first-line chemotherapy after recurrence were 6.7, 30.0 and 42.9% in cohorts A, B and C, respectively, with a significant difference between A and C (p = 0.0007). On multivariate analysis, S-1 adjuvant chemotherapy was independently associated with poor prognosis after recurrence (hazard ratio 2.64). CONCLUSION: S-1 adjuvant chemotherapy significantly reduced survival and response to first-line chemotherapy following recurrence in patients with recurrent gastric cancer.