The impact of dose modification or termination of S-1 as adjuvant therapy on survival of locally advanced gastric cancer underwent curative gastrectomy.

Abstract

193 Background: Adjuvant S-1 therapy for pStage II/III gastric cancer (GC) patients (pts) after curative resection is standard treatment in Japan, however, prognosis of pStage III is still poor. There are few reports investigating the association of treatment exposure with survival. Therefore, we investigated the impact of dose modification or termination of S-1 as adjuvant therapy on overall survival (OS). Methods: The data of locally advanced GC pts who underwent gastrectomy with D2 lymph-node dissection in Shizuoka Cancer Center between Jan 2007 and Aug 2013 were retrospectively collected. Inclusion criteria were as follows: age 20 to 80 years; ECOG PS 0 or 1; histologically proven adenocarcinoma; pStage III under TNM 7th edition; R0 resection; initiation of S-1 within 56 days after surgery. S-1 was administered for 4 weeks followed by a 2 weeks rest. We defined completion of planned S-1 therapy as continuation of S-1 one year after surgery. Results: One hundred and six pts satisfied inclusion criteria. Pts’ characteristics were as follows: median age, 67 years (range, 38-78); male/female, 77/29 pts; ECOG PS 0/1, 72/34 pts; primary tumor location EGJ/U/M/L, 1/27/45/33 pts; and pStage IIIA/IIIB/IIIC, 25/41/40 pts. Fifty-five pts (51%) needed dose modification (dose reduction and/or schedule alteration). Eighty-two pts (77%) achieved completion of planned S-1 therapy. Five year OS rate was 59.9%. Among potential prognostic factors for OS in univariate analysis (age, PS, pStage, completion of planned S-1 therapy, dose modification), completion of planned S-1 therapy (HR 0.26; 95% CI 0.13-0.51; p < 0.001) and PS 0 (HR 0.52; 95% CI 0.27-0.99; p = 0.048) were good prognostic factors and dose modification was not prognostic factor (HR 1.06; 95% CI 0.53-2.12; p = 0.876) for OS. Conclusions: This study suggested that completion of planned adjuvant S-1 therapy and PS 0 were good prognostic factors for OS and appropriate dose modification might not worsen their prognosis.