Background: The factors that affect the 6-month continuation of adjuvant chemotherapy with S-1 have not been fully evaluated. The objective of this retrospective study was to clarify the risk factors for 6-month continuation of S-1 adjuvant chemotherapy.
Methods: The study selected patients who underwent curative D2 surgery for gastric cancer, were diagnosed with stage 2 or 3 disease, had a serum creatinine level of ≤ 1.2 mg/dl, and received adjuvant S-1 between June 2002 and March 2011.
Results: One hundred of these patients were eligible for the present study. A comparison of 6-month continuation of S-1 stratified by various clinical factors, using the log-rank test, revealed a marginally significant difference in creatinine clearance (CCr) between those patients who continued for 6 months and those who did not. A CCr of 60 ml/min was regarded as the critical point. Uni- and multivariate Cox's proportional hazard analyses demonstrated that CCr was the only significant independent factor for the prediction of 6-month continuation. The 6-month continuation rate was 72.9 % in the patients with CCr ≥ 60 ml/min, and 40.0 % in patients with CCr <60 ml/min (P = 0.015). Adverse events occurred more frequently and earlier in the patients with CCr <60 ml/min than in those with CCr ≥ 60 ml/min.
Conclusions: CCr <60 ml/min was a significant risk factor for 6-month continuation of S-1 adjuvant chemotherapy, even though the renal function was judged as normal by the serum creatinine level. Careful attention is therefore required for S-1 continuation in patients with CCr <60 ml/min.