Clinical impact of postoperative interval until adjuvant chemotherapy following curative gastrectomy for advanced gastric cancer

Background: Adjuvant chemotherapy (AC) following curative gastrectomy for stage II/III gastric cancer (GC) is recommended in Japan. However, for various reasons, patients cannot always start AC at the appropriate time. This study was designed to investigate the effect of the postoperative interval until adjuvant chemotherapy (PIAC) and cumulative S-1 dose on prognosis. Methods: Between 2008 and 2014, consecutive 81 GC patients who underwent postoperative S-1 monotherapy were enrolled in this study. Results: Postoperative complications of Clavien-Dindo grade II or higher and postoperative peak C-reactive protein of 8.1 mg/dl or higher were significantly associated with delayed AC. The cut-off value of PIAC selected to most effectively stratify prognosis was 7 weeks. For relapse-free survival (RFS), patients with PIAC ≥ 7 weeks had an insignificantly poorer prognosis than those with PIAC < 7 weeks. A multivariate analysis showed that PIAC ≥ 7 weeks [p = 0.024; hazard ratio (HR) 2.45] and the cumulative S-1 dose/body surface area (BSA) ≥ 12,000 mg/m(2) [p = 0.004; HR 3.27] were independent prognostic factors. In patients with the cumulative S-1 dose/BSA ≥ 12,000 mg/m(2), there were no prognostic differences between patients with and without PIAC ≥ 7 weeks. Conclusions: Seven weeks after surgery could be a limit indicator starting AC. A cumulative S-1 dose/BSA of more than 12,000 mg/m(2) might be a key dose for diminishing the poor prognostic effects of delaying AC.