Pharmacokinetics, Safety, and Efficacy of Trastuzumab Administered Every Three Weeks in Combination With Paclitaxel

Abstract

Purpose: This phase II study evaluated the pharmacokinetics and safety of trastuzumab and paclitaxel given every 3 weeks to women with human epidermal growth factor receptor 2 (HER2)-overexpressing metastatic breast cancer. Patients and Methods: Thirty-two patients received a loading dose of trastuzumab 8 mg/kg intravenously (day 1) and paclitaxel 175 mg/m2 (day 0). Thereafter, trastuzumab 6 mg/kg was administered on the same day as paclitaxel 175 mg/m2 every 3 weeks for seven cycles. In responding patients, trastuzumab monotherapy every 3 weeks was then continued until disease progression or patient withdrawal. Results: Trastuzumab trough levels were more than 20 μg/mL by the end of cycle 1. The half-life of trastuzumab was estimated to be 18 to 27 days, although this may be an underestimate. The combination of paclitaxel and trastuzumab was generally well tolerated, with no unexpected toxicities and no pharmacokinetic interaction. The most common adverse events were myalgia, paresthesias, alopecia, arth...