Oral Irinotecan Regimen Active in Heavily Pretreated Metastatic Breast Cancer

TYLER, TEXAS-A 5-day course of oral irinotecan(Drug information on irinotecan) (Camptosar) given every 3 weeks is active in patients with metastatic breast cancer after the failure of prior anthracycline, taxane, and capecitabine(Drug information on capecitabine) (Xeloda) regimens, Svetislava J. Vukelja, MD, reported (abstract 562). Dr. Vukelja of the Tyler Cancer Center, in Tyler, Texas, presented results of a phase II study of a 5-day, 60 mg/m²/day irinotecan regimen vs a 14-day, 30 mg/m²/day schedule. "Oral irinotecan offers patients convenience and provides protracted drug exposure. Following reported activity of IV irinotecan in refractory metastatic breast cancer, this study evaluates efficacy and safety of two oral irinotecan schedules after failure of prior anthracycline (A), taxane (T), and capecitabine (C)," Dr. Vukelja said. Primary Endpoints The primary study objective was to determine the confirmed objective response rate of single-agent oral irinotecan in this population. Secondary endpoints were response duration, time to tumor progression, overall survival, and safety. Inclusion criteria were histologically confirmed, measurable metastatic breast cancer and failure of prior A, T, or C regimens (progression during or following treatment, lack of response after four cycles, or significant treatment- related toxicity). Patients were randomized to receive oral irinotecan at 60 mg/m² on days 1-5 (Dx5), repeating every 21 days, or 30 mg/m² on days 1-14 (Dx14), repeating every 21 days. Acceptable Safety Profile At the time of this report, 84 of 87 patients on the 5-day arm and 39 of 40 patients on the 14-day arm were evaluable for response. The confirmed response rate (complete plus partial responses) was 14.3% on the 5-day regimen and 7.7% on the 14-day regimen. The 5-day arm had an acceptable safety profile. Grade 3/4 drug-related adverse events included diarrhea (27.6% grade 3), fatigue (13.8% grade 3, 1.1% grade 4), neutropenia (10.3% grade 3, 2.3% grade 4), and vomiting (12.6% grade 3, 0% grade 4). Drugrelated adverse events resulted in hospitalization in 9.2% of patients but no deaths. The 14-day regimen was less well tolerated. There were five treatmentrelated deaths (septic shock, renal failure) and higher rates of grade 3/4 diarrhea (42.4% grade 3, 7.5% grade 4) and hospitalization due to drug-related adverse events (27.5%). "Oral irinotecan is active in heavily pretreated patients with metastatic breast cancer after failure of prior treatment with anthracycline, taxane, and capecitabine (median five prior regimens). Overall response rate was 14% for the 5-day schedule and 8% for the 14-day schedule. The 5-day dosing schedule appears to be better tolerated than the 14-day schedule."