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.