Docetaxel and paclitaxel in breast cancer therapy: present status and future prospects

The taxoids are important novel drugs in the treatment of patients with metastatic breast cancer, including those patients with extensive prior therapy and even patients with anthracycline-refractory disease. The emerging role of taxoid therapy and its optimal integration into new treatment strategies for patients with breast cancer is a major focus of active clinical and laboratory research. The incomplete clinical cross-resistance with anthracyclines observed thus far with both paclitaxel and docetaxel is particularly encouraging, as therapeutic options for patients after anthracycline failure are few and often of limited clinical value. Results of ongoing randomized multicenter trials addressing important clinical questions of optimal dose level, infusion duration, definition of worthwhile combinations, and comparative efficacy and tolerability of taxoid monotherapy or combination therapy with other standard regimens will, in the near future, provide guidelines for the best use of these drugs. Beyond the demonstrated single-agent activity of the taxoids in metastatic breast cancer, trials evaluating the taxoids in combination with various chemotherapeutic agents and monoclonal antibodies are in progress. Pharmacokinetic evaluation of the taxoids as monotherapy and in combination should help to define optimal and safe drug delivery. Clinical and laboratory studies will ultimately define clinically relevant mechanisms of resistance to this class of drugs, and may thus direct the development of rational strategies to overcome resistance and/or to guide analogue development. Finally, follow-up of women participating in present randomized adjuvant trials evaluating the taxoids will determine the potential impact of these important agents on the curability of early stage breast cancer.