[Early phase II study of S-1 in patients with advanced head and neck cancer. S-1 Cooperative Study Group (Head and Neck Working Group)].

In developing new anticancer agents, the most important thing is the balancing of antitumor activity and toxicity. To achieve high activity and low toxicity, S-1 was designed, in which tegafur, prodrug of 5-FU, was combined with two classes of modulators. CDHP, inhibitor of 5-FU degradation in liver and Oxo, inhibitor of 5-FU phosphoribosylation in digestive tract, respectively. This cooperative study with 15 nation-wide institutes was conducted to evaluate the antitumor activity and toxicity of S-1 in patients with advanced head and neck cancer from Jan. 1994 to March 1996 in Japan. Out of 26 patients, CR was achieved in 1 and PR in 11 with a response rate of 46.2%, while adverse events of grade 3 were as follows: hemoglobinemia (7.7%), leukocytopenia, neutropenia, stomatitis and anorexia (3.8%), each. Neither grade 4 adverse event nor treatment-related deaths were observed. Based on these findings, it was concluded that S-1 is a useful anticancer agent with the low grade toxicities for treatment of the patients with advanced head and neck cancer, and the effects of CDHP and Oxo found in preclinical studies might be also reflected in these results.