Longterm control of advanced and recurrent gastric cancer (ARGC) by S-1

An oral tegafur compound, S-1 (TS-1), was developed to potentiate antitumor activity and to reduce gastrointestinal toxicities for patients with gastric cancer. It has achieved a high response rate against advanced and recurrent gastric cancer (ARGC) in Japan; however, the efficacy and adverse reactions of longterm administration of S-1 remain to be elucidated.

Sixty-nine patients with ARGC treated with S-1 were studied; 58 patients had measurable lesions, while 11 patients did not. S-1 was orally administered at doses of between 40 and 60 mg/body twice daily for 28 days, followed by 14 days' rest, as one course.

The overall response rate was 38% (complete response [CR], 2/58; partial response [PR], 25/58; stable disease [SD], 9/58 progressive disease [PD] 23/58). Response rate by target organ was 40% for the primary lesion, 45% for lymph node metastasis, 38% for peritoneal metastasis, and 25% for liver metastasis. When S-1 was administered as second-line chemotherapy (n = 25), the response rate was 36%. Of the 69 patients, 14 received S-1 for more than a year. The median survival time (MST) after S-1 administration in these 14 patients, including 3 patients with stable disease, was 918 days (range, 536 to 1107 days). There were no grade 3 to 4 toxicities in these 14 patients receiving longterm therapy with S-1.

S-1 therapy was performed with a high response rate, irrespective of the target organ or the presence of prior chemotherapy. Longterm administration of S-1 may benefit patients with ARGC, providing prolonged disease control with acceptable toxicities.