Phase II study of S-1 as first-line treatment for elderly patients over 75 years of age with advanced gastric cancer: the Tokyo Cooperative Oncology Group study.

Purpose: This prospective multicenter phase II study was carried out to investigate the efficacy, safety and pharmacokinetics of S-1 monotherapy in elderly patients over 75 years of age, with unresectable advanced or recurrent gastric cancer.

Methods: Patients had measurable or evaluable lesions according to the Japanese Classification of Gastric Carcinoma. S-1 (25-60 mg determined by the body surface area and creatinine clearance) was given orally, twice daily. A course of treatment consisted of 4-week administration followed by a 2-week rest period, and the patients received repeated courses.

Results: Thirty-three patients were enrolled. Pharmacokinetics of S-1 was studied in six patients, and the maximum plasma concentrations of respective metabolites after S-1 administration were found to be similar to those reported for younger cancer patients. The overall response rate in 33 patients was 21.2% (95% CI, 10.7-37.8%), and median progression-free survival was 3.9 months, with a median overall survival of 15.7 months. Frequently noted adverse events include leukopenia, neutropenia, anemia, anorexia, and fatigue. As for serious adverse events, relatively higher frequencies of anemia (9%) and anorexia (12%) of grade 3 severity were found, but there were no grade 4 episodes.

Conclusions: The results suggest that S-1 monotherapy is safe and useful for elderly patients with unresectable advanced or recurrent gastric cancer when the dose is selected with caution, taking into account renal function.