Phase I study of taxol using a 5-day intermittent schedule.

Taxol is a plant product derived from the western yew, Taxus brevifolia. We have conducted a phase I clinical study of Taxol used intravenously daily for 5 days at 3-week intervals. The starting dose was 5 mg/m2 daily, and the highest dose used was 40 mg/m2 daily for 5 days. The daily dosage of Taxol was mixed in 250 mL of intravenous fluid and infused over a period of 1 hour. A total of 20 patients with metastatic solid tumors refractory to standard therapy received 45 courses of therapy. Taxol was generally well tolerated and caused no significant nausea or vomiting. A mild degree of diarrhea was reported by six patients, and a moderate degree of stomatitis at the higher dose levels developed in four patients. All patients treated in the dosage range of 20 mg/m2 to 40 mg/m2 experienced nearly complete alopecia. Myelosuppression, predominantly in the form of leukopenia, was the dose-limiting toxicity. The nadir of leukopenia was reached between days 8 and 12 followed by complete recovery between days 15 and 21. Leukopenia was first observed following the Taxol dosage level of 20 mg/m2/d, was moderately severe at the dosage level of 30 mg/m2/d, and was severe at the dosage level of 40 mg/m2/d. No objective tumor regression was observed. A starting dosage level of 30 mg/m2/d for 5 days is recommended for phase II trials using this schedule.