661P - A phase II study for triplet combination of oxaliplatin, irinotecan, and S-1 in patients with metastatic or recurrent gastric cancer

Abstract

Doublet chemotherapy of platinum and 5-fluorouracil is considered as a standard front-line treatment for patients with unresectable gastric cancer. Although addition of taxane or irinotecan to this regimen has yielded promising efficacy, it has been used in limited patients due to severe toxicities. To overcome this limitation, we evaluated the efficacy and safety of the combination of irinotecan, oxaliplatin, and S-1 for the treatment of unresectable gastric cancer. Chemotherapy-naïve patients with pathologically proven unresectable recurrent or metastatic gastric adenocarcinoma were assessed for eligibility. Irinotecan at 135 mg/m2 and oxaliplatin at 65 mg/m2 were administered intravenously on day 1, and S-1 was administered orally at 80 mg/m2 on days 1–7 of every 14-day cycle, which have been derived from our phase I study. Forty-three patients (median age 57 years) were enrolled. A total of 259 cycles of chemotherapy were administered (median of eight; range 1–23 cycles). Toxicities were evaluated in 41 patients, and the responses were evaluated in 32 patients. Major toxicities included grade 3/4 neutropenia (41.5%), febrile neutropenia (14.6%), abdominal pain (12.2%), and diarrhea (7.3%). The overall response rate was 59.4% [95% confidence interval (CI) 42.3-74.5%]. The median progression-free survival and overall survival were 8.4 months (95 % CI 5.5-11.3 months) and 13.1 months (95 % CI 11.8–14.5 months), respectively. These data suggest that the oxaliplatin, irinotecan, and S-1 combination regimen is effective and relatively well tolerable, and it seems to have potential to be a reasonable therapeutic strategy in patients with unresectable gastric cancer.