Ixabepilone and Carboplatin for Hormone Receptor Positive/HER2-neu Negative and Triple Negative Metastatic Breast Cancer

Abstract

Background: Hormonal therapies and single-agent sequential chemotherapeutic regimens are the standards of care for HER2^- metastatic breast cancer (MBC). However, treating patients with hormone-refractory and triple negative (TN) MBC remains challenging. We report the results of combined ixabepilone and carboplatin in a single-arm phase II trial.

Patients and methods: In the present prospective analysis of hormone receptor-positive (HR⁺)/HER2^- and TN MBC cohorts, patients could have received 0 to 2 chemotherapy regimens for MBC before enrollment. All patients received ixabepilone 20 mg/m² and carboplatin (area under the curve, 2.5) on days 1 and 8 every 21 days. The primary endpoint was the objective response rate (ORR). The secondary objectives included progression-free survival (PFS), clinical benefit rate (CBR), overall survival (OS), and toxicity.

Results: We enrolled 54 HR⁺ and 49 TN patients (median, 1 previous chemotherapy regimen for metastatic disease; most in addition to adjuvant chemotherapy). The ORR was 34% and 30.4% for the HR⁺ and TN patients, respectively, with a corresponding CBR of 56.6% and 41.3%. The ORRs were similar in taxane-pretreated patients (ORR, 31.4% and 28.6% for HR⁺ and TN patients, respectively). The median OS was 17.9 months for HR⁺ patients and 12.5 months for TN patients. The median PFS was similar for both groups at 7.6 months. Grade 3/4 nonhematologic toxicities included neuropathy (9%) and fatigue (8%). Nine patients developed grade 3/4 neuropathy, 7 of whom had received previous taxane treatment.

Conclusion: Ixabepilone plus carboplatin is active even in later-line HR⁺ and TN disease. Toxicities were manageable without cumulative myelosuppression. This combination is a reasonable option for those patients with MBC who require combination chemotherapy.

Keywords: Carboplatin; HR+; Ixabepilone; MBC; TNBC.