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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.

In phase I and II studies we administered fixed doses of doxorubicin by intravenous bolus 16 hours before escalating doses of paclitaxel (Taxol; Bristol-Myers Squibb Company, Princeton, NJ) for the treatment of patients with advanced breast cancer who had received no prior treatment or who had relapsed after adjuvant therapy. Nineteen patients were entered in the study from April 1994 to February 1995. The median age of participants was 54 years; the median disease-free interval was 328 days. Eleven patients had undergone prior adjuvant chemotherapy, seven had undergone prior hormonal therapy, and six had undergone chest radiotherapy. A total of 128 courses of fixed-dose doxorubicin 50 mg/m2 by intravenous bolus and paclitaxel (doses escalated from 130 to 250 mg/m2, through dose escalations of 30 mg/m2 if maximum tolerated dose was not reached) were repeated every 21 days for a median of seven cycles per patient. Toxicities encountered in this trial included grade 4 neutropenia (20% of courses) and grade 4 thrombocytopenia (3% of courses). No grade 3 or 4 nonhematologic toxicities were observed (World Health Organization grade I peripheral neuropathies and mild myalgias in 37.5% and 30% of courses, respectively). No cardiac toxicity was observed. Responses included six complete responses (31.6%), nine partial responses (47.2%), and three stable disease (15.8%), for an overall response rate of 78.8%. Median duration of overall and complete response was 8+ months and 7+ months, respectively. At dose levels > or = 190 mg/m2, all patients had achieved a response (six complete responses and six partial responses). A phase II trial using fixed doses of doxorubicin (50 mg/m2) and paclitaxel (220 mg/m2) is ongoing. Preliminary data on 71 courses report no cardiac toxicity. Treatment with paclitaxel has been well tolerated at each dose level. The maximum tolerated dose was not reached at 250 mg/m2. No cardiac toxicity was reported. The dosing sequence of doxorubicin followed by paclitaxel is a highly active regimen and needs to be tested in anthracycline patients and in an adjuvant setting.

Based on preclinical data, we designed a phase I/II clinical trial to determine the efficacy and toxicity of doxorubicin followed by paclitaxel (Taxol; Bristol-Myers Squibb Company, Princeton, NJ) in the treatment of patients with advanced breast cancer (either untreated or relapsed after adjuvant therapy). In the phase I study, 19 enrolled patients received bolus doxorubicin (50 mg/m2) and, after a 16-hour interval, escalating doses of paclitaxel (from 130 to 250 mg/m2 in 30-mg/ m2 increments) by 3-hour infusion every 3 weeks for a maximum of eight cycles. Paclitaxel doses were increased if the maximum tolerated dose (MTD; defined by dose-limiting toxicities) had not been reached. Analysis of the 128 cycles assessable for toxicity demonstrated neutropenia (< 500/microL) in 20% of cycles with no significant clinical events. No relevant clinical cardiotoxicity was observed. Other toxicities included mild peripheral neuropathy and mild myalgia/arthralgia (In 37.5% and 30.4% of cycles, respectively). The maximum tolerated paclitaxel dose was not reached at the 250 mg/m2 dose level. In the second phase, 13 patients were treated with fixed doses of both drugs (doxorubicin 50 mg/m2 and paclitaxel 220 mg/m2, the dose level immediately preceding the highest paclitaxel dose used in phase I). Grade 4 neutropenia occurred in 36 of the 87 cycles but was complicated by fever in only eight cycles (9%); three patients needed granulocyte colony-stimulating factor. Peripheral neuropathy (grades 1 and 2 in 41.3% and 5.7% of cycles, respectively) and a myalgic syndrome (grades 1 and 2 in 24.1% and 17.2% of cycles, respectively) were observed. No significant clinical cardiotoxicity was observed in 12 of the 13 patients. One patient experienced a decrease in left ventricular ejection fraction (from 60% to 43%) at a cumulative doxorubicin dose of 400 mg/m2. Antitumor efficacy was evaluated in both phase I and phase II. Overall clinical responses included 10 complete (31.3%) and 15 partial (46.9%) responses, for an objective response rate of 78.1%. Six patients (18.8%) had stable disease. The median durations of objective and complete response were 9 and 7 months, respectively. The 78.9% objective response rate in the phase I trial (31.6% complete and 47.3% partial responses) suggests a dose response relationship: at paclitaxel dose > or = 190 mg/m2, all patients had an objective response (six complete and nine partial responses). These results confirm that doxorubicin followed by paclitaxel is active and should be tested as adjuvant treatment and in patients treated previously with anthracyclines.