Capecitabine in breast cancer: current status

Anthracyclines, together with taxanes, are at present the most active agents in metastatic breast cancer, while single-agent, bolus 5-fluorouracil (5-FU) is not very active in this setting. In view of encouraging results and tolerable toxicity of continuous infusion of 5-FU in gastrointestinal cancer, innovative oral 5-FU agents such as capecitabine have been developed. Capecitabine is a prodrug that is converted into the active compound 5-FU preferentially at the tumor site. An intermittent dosing schedule of capecitabine twice daily at a dose of 2510 mg/m2/day on days 1-14 in a 3-week cycle appeared to be feasible and resulted in a high dose intensity. A large phase II study investigating capecitabine in 135 advanced breast cancer patients, pretreated with anthracyclines and taxanes, observed three complete and 24 partial responses (response rate, 20%), with a mean duration of 8.0 months. Preliminary results of a study comparing capecitabine with paclitaxel in 42 breast cancer patients failing anthracyclines indicate that the efficacy of capecitabine is comparable to that of paclitaxel, with response rates of 36% and 21%, respectively. Another study reported a response rate of 25% for capecitabine as first-line therapy for advanced breast cancer in women aged > or = 55 years, which tended to be better than combination chemotherapy with cyclophosphamide/methotrexate/5-FU. In all studies, capecitabine side effects were mainly mild, and treatment-related grade 3/4 toxicity consisted of diarrhea (8%-11%), nausea (4%-11%), hand-foot syndrome (10%-18%), neutropenia (3%-20%), and bilirubin elevation (6%). Capecitabine is clearly an active agent for the treatment of breast cancer. It is currently registered in various countries for use in third-line treatment of metastatic disease. Its further role will have to be defined from data of randomized phase III studies.