Combination chemotherapy with paclitaxel and doxorubicin for metastatic breast cancer

The development of anthracycline/paclitaxel (Taxol; Bristol-Myers Squibb Company, Princeton, NJ) combinations has gone through several phases or generations. The first dose escalation studies used prolonged infusions of doxorubicin (48 to 72 hours) and paclitaxel (24 hours). Myelosuppression, mucositis, and neutropenic fever were dose limiting, and a sequence-dependent interaction was noted. In a second phase, doxorubicin was administered by bolus, without changing the schedule of the taxane. More recently, bolus doxorubicin was combined with 3-hour paclitaxel infusions. Higher doses of both agents were administered in this latter schedule, with higher overall response rates reported. Excessive cardiac toxicity was reported with the initial trials that used this schedule. Confirmatory studies are under way pursuing several alternatives to reduce the risk of cardiac toxicity; these include limiting the cumulative dose of doxorubicin, inserting an interval between the administration of the two drugs, and adding a cardioprotective agent to the combination. The high degree of antitumor activity of this combination is quite encouraging, and additional evaluation of this regimen in controlled trials is warranted in metastatic and high-risk primary breast cancer.