In this phase I trial, 42 women with metastatic breast cancer were treated with a fixed dose of epirubicin (75 mg/m2) and escalating doses of ixabepilone (25, 30, and 35 mg/m2). The maximum-tolerated dose of ixabepilone in combination with epirubicin was 30 mg/m2 (the recommended dose for phase II evaluation), and the dose-limiting toxicity dose was 35 mg/m2 with grade 4 neutropenia.
Purpose: The objectives of this phase I trial were to determine the maximum-tolerated dose (MTD), toxicity profile, dose-limiting toxicities (DLT), pharmacokinetics, and the recommended phase II dose for ixabepilone in combination with epirubicin in women with metastatic breast cancer.
Patients and methods: Patients ≥18 years old with an histologically or cytologically confirmed diagnosis of invasive breast cancer and clinical evidence of locally recurrent or metastatic disease were enrolled and treated with a fixed dose of epirubicin (75 mg/m(2)) and escalating doses of ixabepilone (25, 30, and 35 mg/m(2)).
Results: Forty-two women were treated at 3 different dose levels of ixabepilone: 25 (n = 6), 30 (n = 30), and 35 mg/m(2) (n = 6) in combination with 75 mg/m(2) epirubicin. The MTD of ixabepilone in combination with epirubicin 75 mg/m(2) was 30 mg/m(2), and the DLT dose was 35 mg/m(2) with grade 4 neutropenia. Grade 3/4 neutropenia was the most frequent moderate-to-severe adverse event and was manageable and reversible. No deaths were reported. Objective responses were achieved in 18 of 32 patients with measurable disease (56% [90% CI, 40%-71%]) and in 9 of 22 evaluable patients treated at the MTD (41% [90% CI, 23%-61%]). Ixabepilone clearance and the epirubicin pharmacokinetic profile were similar across ixabepilone dose levels.
Conclusions: The combination of ixabepilone and epirubicin was clinically active. The recommended dose for evaluation in phase II is epirubicin 75 mg/m(2), followed by ixabepilone 30 mg/m(2) every 3 weeks.
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