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

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/m 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.