Weekly ixabepilone administration in heavily pretreated metastatic breast cancer patients

Ixabepilone 40 mg/m² administered on an every 3-week schedule is approved for use in metastatic breast cancer (MBC) as monotherapy, or in combination with capecitabine in anthracycline/taxane resistant tumors. Because the mechanism of action and toxicity profile is similar to the taxanes, it has been suggested that weekly administration (15–20 mg/m² on days 1, 8, 15 for 28 days/cycle) may provide a therapeutic advantage while minimizing toxicity. We report 24 MBC patients treated with weekly ixabepilone. Demographics, ER/PR/HER-2/neu, ECOG performance status (PS), sites of metastatic disease, lines of previous therapy, dosage, treatment duration, dose reductions/interruptions, hematologic/non-hematologic toxicities, growth factor use, reasons for discontinuation, time to progression (TTP), and response rate were recorded. Median age was 61 years (33–79). 0–1 ECOG PS was 54%. Sixty-seven percent of patients received ≥4 previous chemotherapy regimens. Median treatment duration was 1.4 months (0.5–10.8). Median dose was 16 mg/m² (15–20). In 37.5% of patients, the dose was held due to toxicities with median missed dose of 2. Partial response and stable disease were 4 and 48%. Median TTP was 2.1 months (0.9–16.4). Majority of patients discontinued therapy due to disease progression (84%). Grade 3–4 neutropenia and neuropathy were 4% and 8%. It is not yet clear whether the weekly administration of ixabepilone impacts the risk/benefit profile. There are clinical data to suggest that weekly ixabepilone is efficacious and tolerable. Upcoming clinical trials will continue to inform the question. Our data suggest that weekly ixabepilone is well tolerated with a manageable side-effect profile in this small, heavily pretreated population.