S-1 Monotherapy as a Neoadjuvant Treatment for Locally Advanced Gastric Cancer

S-1, a novel oral fluoropyrimidine, is an effective therapeutic agent for gastric cancer. Herein, we report a case with locally advanced gastric cancer that achieved a curative resection after S-1 monotherapy as neoadjuvant treatment. A 68-year-old man was diagnosed with gastric cancer and massive lymphadenopathy involving the perigastric, celiac axis and splenic hilum. His clinical stage was cT3N2H0P0M0. Considering his relatively poor performance (ECOG 2, severe weight loss) and advanced age, we started the patient on S-1 monotherapy at a dose of 35 mg/m2 bid for 4 consecutive weeks followed by a 2-week rest. Follow-up study after 4 treatment cycles revealed disappearance of the lymphadenopathy of the perigastric and celiac axis with diminished extension of the stomach mass. The patient had a partial response (PR) with a 72% tumor reduction, according to the Response Evaluation Criteria in Solid Tumors (RECIST). His performance status was improved to an ECOG 1 and he gained 7 kg. A curative (R0) resection was achieved with a radical total gastrectomy and D2 dissection. The pathological stage was pT3N2M0, stage IIIB. In conclusion, S-1 neoadjuvant chemotherapy aided in the treatment of gastric cancer in this patient.ope