Taxoids in combination chemotherapy for metastatic breast cancer

The rationale for the development of new drug combinations is to combine optimal doses of drugs with single agent activity which are not cross-resistant and have non-overlapping toxicities. Anthracyclines are widely accepted as the agents of choice for first-line treatment of metastatic breast cancer and have been tested in combination with the taxoids, docetaxel (Taxotere) and paclitaxel (Taxol). Toxicity problems have emerged using anthracyclines and paclitaxel, with sequence- and schedule-dependent toxic effects including dose-limiting typhlitis and mucositis, as well as febrile neutropenia and, in one study, cardiomyopathy. The dose-limiting toxicities of the combination of docetaxel and doxorubicin are neutropenia and infection, and preliminary results indicate a response rate of 89%. There is a need to develop a combination treatment regimen which is non-cross-resistant with anthracyclines. Vinorelbine (Navelbine) has single agent activity against metastatic breast cancer and has been used in combination with taxoids. The dose-limiting toxicities of the vinorelbine-paclitaxel combination are febrile neutropenia, pelvic pain, fatigue and paraesthesias. The dose-limiting toxicities of the combination of docetaxel and vinorelbine are febrile neutropenia and mucositis. The overall response rate for this combination was 67% and studies are ongoing.