Clinical effect of irinotecan in advanced and metastatic breast cancer patients previously treated with doxorubicin- and docetaxel-containing regimens

Background: Previous phase II trials in Japan suggested that irinotecan was a promising agent for advanced or metastatic breast cancer pretreated with anthracycline. However, irinotecan has not yet been evaluated in the salvage setting for breast cancer pretreated with both anthracycline and taxane, which are two active agents for breast cancer. Methods: The efficacy and safety of irinotecan were retrospectively evaluated in patients with breast cancer who had previously been treated with both doxorubicin and docetaxel. From 1996 to 1999, irinotecan was administered to 20 patients, all with a performance status of <2. Irinotecan treatment was repeated in ∼6 week cycles consisting of the administration of irinotecan once weekly for 4 weeks followed by a 2 week rest. The median dose of irinotecan administered was 100 mg/m² weekly. The median number of irinotecan cycles given was 1 (range: 1-8 cycles). The median total dose was 388 mg/m² (range: 50-2400 mg/m²). Results: Performance status declined to >3 after treatment with irinotecan in four patients. Two patients had grade 3 leukopenia; three had grade 3 anemia and one had a creatinine elevation of grade 4. The objective response rate for all patients was 5.0% (95% CI: 0-15.5%). The median time to progression and overall survival were 35 days (range: 17-285 days) and 124 days (range: 17-667 days), respectively, since the start of the administration of irinotecan. Conclusions: Salvage chemotherapy with irinotecan may be inactive against advanced and metastatic breast cancer pretreated with doxorubicin and docetaxel. We will evaluate irinotecan for advanced and metastatic breast cancer patients as first- or second-line chemotherapy combined with anthracycline or taxane.