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Summary This study set out to evaluate, in patients with metastatic colorectal carcinoma, the efficacy and toxicity of S-1, which contains tegafur, 5-chloro-2,4-dihydroxypyridine (CDHP) and potassium oxonate, based on a biochemical modulation of 5-fluorouracil (5-FU) targeted at inhibition of dihydropyrimidine dehydrogenase (DPD). Sixty-three patients with measurable metastatic colorectal carcinoma were enrolled into the study. None of the patients had received prior chemotherapy except for adjuvant setting. S-1 was administered orally twice daily at a standard dose of 80 mg m -2 day -1 for 28 days followed by a 14-day rest. This agent is continued until disease progression, unaccepted toxicity, or patient refusal. Twenty-two (35%) of the 62 eligible patients achieved PR with a 95% confidence interval of 25-48%. Five of the 10 patients with a history of adjuvant chemotherapy achieved partial remission. The median survival time was 12 months. Major adverse reactions included myelosuppressive and gastrointestinal toxicities, though their incidence of grade 3 or 4 being 13% in neutropenia and less than 10% in the others. None of the 53 patients treated as outpatients required hospitalization due to adverse reactions: These results suggest that S-1 achieves similar responses to those of infusional 5-FU plus leucovorin and shows the potential of another biochemical modulation with easily manageable toxicity.

5-Fluorouracil (5-FU) or a 5-FU derivative 1-(2-tetrahydrofuryl)-5-fluorouracil (FT) has been widely prescribed for patients with gastrointestinal cancer. However, the phosphorylation of 5-FU in the digestive tract causes gastrointestinal toxicities. 5-FU is also rapidly degraded to α-fluoro-β-alanine after contact with dihydropyrimidine dehydrogenase (DPDase) which is mainly present in the liver. Therefore, to overcome these metabolic events, S-1, an antitumor agent was developed, based on the biochemical modulation of FT by 5-chloro-2,4-dihydroxypyridine (CDHP) and potassium oxonate (Oxo), in a molar ratio of 1:0.4:1. The antineoplastic effect of S-1, was examined in Japanese patients with advanced gastric (G) or colorectal (C) cancer in a multicenter early phase II study involving 24 centers throughout Japan. The patients were prescribed a minimum of 2 courses of S-1 orally, with each course consisting of 75 or 50 mg (in terms of FT) twice a day for 28 days followed by withdrawal for 2 weeks. Thirty-one patients with G and 31 C were entered into this study. The clinical response and extent of toxicity were evaluated in G 28 and C 30 cases, respectively. Nine (32.1%) G patients and 14 (46.7%) C patients had been treated previously with other anticancer drugs. In G patients, there was a 53.6% (15/28) and in C patients a 16.7% (5/30) response rate (90% confidence interval G 38.4–68.1% and C 8.4–30.5%) with 15 (53.6%) (G) and 5 (16.7%) (C) partial responses (PR), and these responses persisted for 79 days (G) and 120 days (C) (median value). In particular, the response rate for the primary lesion was 27.8% (5/18) (G) and 33.3% (1/3) (C). No change (NC) in the disease was observed in 4 (14.3%) (G) and 13 (43.3%) (C) patients, and in 6 (21.4%) (G) and 7 (23.3%) (C) the disease progressed (PD). At the time of analysis, the median survival was 298 days (G) and 358 days (C). Major adverse effects consisted of gastrointestinal symptoms and myelosuppression while toxicities of grade 3 or more occurred in 35.7% (10/28) (G) and 33.3% (10/30) (C). Based on these data, S-1 is considered to have positive effects in patients with advanced gastrointestinal cancer.

BACKGROUNDThe goal of the current study was to evaluate the objective response rate and toxicity associated with the oral fluoropyrimidine S‐1 (a combination of tegafur, 5‐chloro‐2,4‐dihydroxypyridine, and potassium oxonate) in patients with previously untreated metastatic colorectal carcinoma.METHODSThirty‐eight patients were enrolled in the study. S‐1 was administered orally at a dose of 40 mg/m2 twice daily for 28 days, followed by a 14‐day rest period. Treatment was repeated every 6 weeks unless disease progression was observed.RESULTSA combined total of 173 courses of S‐1 were administered to the 38 enrolled patients. The median number of courses administered to a given patient was 3.5 (range, 1–18). Although no patient exhibited a complete response to treatment, 15 had partial responses (response rate, 39.5%; 95% confidence interval, 24.0–56.6%). In addition, 5 patients had minor responses, and 14 had stable disease. Four patients were found to have progressive disease after two courses of treatment. The median survival time was 358 days (95% confidence interval, 305–490 days), and the 1‐year survival rate was 47.4%. The most common adverse reactions included myelosuppression and gastrointestinal toxicity; most cases involved Grade 1 or 2 toxicity, but Grade 3 toxicities (anemia [7.9% of patients], neutropenia [5.3% of patients], diarrhea [2.6% of patients], and abnormal bilirubin levels [7.9% of patients]) also were noted. Neither Grade 4 toxicity nor treatment‐related death was observed during the study.CONCLUSIONSOrally administered S‐1 is active against metastatic colorectal carcinoma and has an acceptable toxicity profile. This promising agent has the potential to become a valuable chemotherapeutic option. Cancer 2004. © 2004 American Cancer Society.

Purpose: The Japanese Foundation for Multidisciplinary Treatment of Cancer conducted a Phase I study of a novel oral fluorouracil derivative, S-1, combined with a low dose of cisplatin in unresectable and recurrent gastric cancer.Experimental Design: S-1 was administered orally at 80 -120 mg/body/day, depending on body surface area. One course consisted of consecutive administration for 28 days followed by a rest of 14 days. Low-dose cisplatin was given i.v. on days 1-5, 8 -12, 15-19, and 22-26 of each course. The dose escalation of cisplatin began with an initial dose of 1 mg/m 2 /day as level 1 and was stepped up to 2, 3, 4, and 6 mg/m 2 /day as level 2, 3, 4, and 5, respectively. The regimen was repeated for at least two courses.Results: A total of 24 patients was entered in the study. There was no treatment-related death. At level 5, consisting of 5 evaluable patients, dose-limiting toxicity was experienced as grade 3 appetite loss in 2 patients and grade 4 neutropenia in 1 patient. The maximum-tolerated dose of cisplatin was estimated to be 6 mg/m 2 /day. We decided on a recommended dose of cisplatin of 4 mg/m 2 /day because the dosage was one level under the maximum-tolerated dose. All 3 patients at level 4 showed partial response, suggesting promising clinical efficacy with this dosage. The serum concentration of cisplatin at level 4 was 918 ؎ 92 ng/ml on day 26 of the first course.Conclusions: S-1 with low-dose cisplatin may become an effective regimen with acceptable toxicity for gastric cancer.