Paclitaxel plus doxorubicin in breast cancer: an Italian experience

Based on preclinical data, phase I/II clinical trials were performed at Istituto Oncologico Romagnolo (IOR) Operative Units (Medical Oncology Departments of Forlì, Rimini, and Ravenna, Italy) to determine the efficacy and toxicity of sequential administration of doxorubicin followed by paclitaxel (Taxol; Bristol-Myers Squibb Company, Princeton, NJ) in the treatment of patients with advanced breast cancer that either had been previously untreated or that had relapsed after adjuvant therapy. In the phase I trial, 19 patients received bolus doxorubicin (50 mg/m2) followed after a 16-hour interval by paclitaxel (given at dose levels ranging from 130 to 250 mg/m2) by 3-hour infusion every 3 weeks, for a maximum of eight cycles. Paclitaxel doses were escalated in 30-mg/m2 increments if the maximum tolerated dose had not been reached in the previous dose level. Analysis of the 128 cycles assessable for toxicity demonstrated neutropenia (500/microL) in 26 courses (20.3%), with no significant clinical events. No relevant clinical cardiotoxicity was observed. The paclitaxel maximum tolerated dose was not reached at the 250-mg/m2 dose level (no grade 3 or 4 extramedullary toxicity). In the IOR phase II trial, 13 patients were treated with fixed doses of both drugs (doxorubicin 50 mg/m2 and paclitaxel 220 mg/m2). Grade 4 neutropenia occurred in 39 of the 95 cycles, but was complicated by fever in only eight cycles (8.4%); three cycles required granulocyte colony-stimulating factor support. Peripheral neurotoxicity was the most common extramedullary side effect noted. Overall clinical responses in the IOR trials included 10 complete responses (31.3%) and 15 partial responses (46.9%), with an objective response rate of 78.1%. Comparison of these results with those obtained from a phase I trial using the opposite drug sequence showed comparable overall response rates, but IOR's sequence was associated with a higher complete response rate, as well as less frequent and less severe nonhematologic toxicity.