S-1 is a newly developed novel oral dihydrouracil dehydrogenase inhibiting fluoropyrimidine drug consisting of 1 M tegafur ( FT ) , 0.4 M 5-chloro-2 , 4-dihydroxypyrimidine ( gimeracil ) , and 1 M potassium oxonate ( oteracil ) , with efficient antitumor activity and low gastrointestinal toxicity which is widely used in Japan against advanced gastric , head and neck cancers .
A phase II study of S-1 in patients with metastatic breast cancer--a Japanese trial by the S-1 Cooperative Study Group, Breast Cancer Working Group.  S-1 is a newly developed novel oral dihydrouracil dehydrogenase inhibiting fluoropyrimidine drug consisting of 1 M tegafur ( FT ) , 0.4 M 5-chloro-2 , 4-dihydroxypyrimidine ( gimeracil ) , and 1 M potassium oxonate ( oteracil ) , with efficient antitumor activity and low gastrointestinal toxicity which is widely used in Japan against advanced gastric , head and neck cancers . We investigated its clinical efficacy against metastatic breast cancer. ### methods A non-blind phase II study was carried out to evaluate the efficacy and toxicity in metastatic breast cancer patients. Patients with measurable metastasis foci (n=111) were enrolled, and 108 patients were regarded as eligible. S-1 was administered orally at a standard dose of 80 mg/m2/day b.i.d. One course consisted of 28 consecutive days of administration followed by a 14-day rest, and courses were repeated up to six times. ### results Among the eligible patients, 10 had a complete response and 35 had a partial response, with an overall response rate (CR+PR) of 41.7% (95% confidence interval: CI, 32.3-51.5%). The incidences of toxicity (> or =grade 3) were neutropenia 9.1%, anemia 0.9%, anorexia 3.6%, stomatitis 1.8%, nausea/vomiting 1.8%, diarrhea 0.9%, and fatigue 2.7%, however no treatment-related deaths were observed. The median survival time was 872 days (95% CI, 572-1,110 days). There was no difference in response rate or toxicity between the under 65-year-old group and the older group. ### conclusion S-1 was demonstrated to have high efficacy with low gastrointestinal toxicity even in older patients and will be a promising new chemotherapy drug for metastatic breast cancer.
### Instruction:
            Given the context about compound efficacy for the given treatment mentioned within the input, mentioned the compounds 
            that can co-occur for the mentioned treatment

            ### Input:
            A phase II study of S-1 in patients with metastatic breast cancer--a Japanese trial by the S-1 Cooperative Study Group, Breast Cancer Working Group.  S-1 is a newly developed novel oral dihydrouracil dehydrogenase inhibiting fluoropyrimidine drug consisting of 1 M tegafur ( FT ) , 0.4 M 5-chloro-2 , 4-dihydroxypyrimidine ( gimeracil ) , and 1 M potassium oxonate ( oteracil ) , with efficient antitumor activity and low gastrointestinal toxicity which is widely used in Japan against advanced gastric , head and neck cancers . We investigated its clinical efficacy against metastatic breast cancer. ### methods A non-blind phase II study was carried out to evaluate the efficacy and toxicity in metastatic breast cancer patients. Patients with measurable metastasis foci (n=111) were enrolled, and 108 patients were regarded as eligible. S-1 was administered orally at a standard dose of 80 mg/m2/day b.i.d. One course consisted of 28 consecutive days of administration followed by a 14-day rest, and courses were repeated up to six times. ### results Among the eligible patients, 10 had a complete response and 35 had a partial response, with an overall response rate (CR+PR) of 41.7% (95% confidence interval: CI, 32.3-51.5%). The incidences of toxicity (> or =grade 3) were neutropenia 9.1%, anemia 0.9%, anorexia 3.6%, stomatitis 1.8%, nausea/vomiting 1.8%, diarrhea 0.9%, and fatigue 2.7%, however no treatment-related deaths were observed. The median survival time was 872 days (95% CI, 572-1,110 days). There was no difference in response rate or toxicity between the under 65-year-old group and the older group. ### conclusion S-1 was demonstrated to have high efficacy with low gastrointestinal toxicity even in older patients and will be a promising new chemotherapy drug for metastatic breast cancer.

            ### Response:
            tegafur, gimeracil
            