TITAN: phase III study of doxorubicin/cyclophosphamide followed by ixabepilone or paclitaxel in early-stage triple-negative breast cancer

Abstract

Purpose: Ixabepilone is a microtubule stabilizer with activity in taxane-refractory metastatic breast cancer and low susceptibility to taxane-resistance mechanisms including multidrug-resistant phenotypes and high β-III tubulin expression. Since these resistance mechanisms are common in triple-negative breast cancer (TNBC), ixabepilone may have particular advantages in this patient population. This study evaluated the substitution of ixabepilone for paclitaxel following doxorubicin/cyclophosphamide (AC) in the adjuvant treatment of early-stage TNBC.

Methods: Patients with operable TNBC were eligible following definitive breast surgery. Patients were randomized (1:1) to receive four cycles of AC followed by either four cycles (12 weeks) of ixabepilone or 12 weekly doses of paclitaxel.

Results: 614 patients were randomized: 306 to AC/ixabepilone and 308 to AC/paclitaxel. At a median follow-up of 48 months, 59 patients had relapsed (AC/ixabepilone, 29; AC/paclitaxel, 30). The median time from diagnosis to relapse was 20.8 months. The 5-year disease-free survival (DFS) rates of the two groups were similar [HR 0.92; ixabepilone 87.1% (95% CI 82.6-90.5) vs. paclitaxel 84.7% (95% CI 79.7-88.6)]. The estimated 5-year overall survival (OS) rates were also similar [HR 1.1; ixabepilone 89.7% (95% CI 85.5-92.7) vs. paclitaxel 89.6% (95% CI 85.0-92.9)]. Peripheral neuropathy was the most common grade 3/4 event. Dose reductions and treatment discontinuations occurred more frequently during paclitaxel treatment.

Conclusions: Treatment with AC/ixabepilone provided similar DFS and OS in patients with operable TNBC when compared to treatment with AC/paclitaxel. The two regimens had similar toxicity, although treatment discontinuation, dose modifications, and overall peripheral neuropathy were more frequent with AC/paclitaxel.

Trial registration: Clinical Trials.gov Identifier, NCT00789581.

Keywords: Cyclophosphamide; Doxorubicin; Ixabepilone; Triple-negative breast cancer.