Purpose: The study was undertaken to assess the antitumor activity of carboplatin 400 mg/m2 intravenously every 4 weeks in metastatic breast cancer (MBC).
Patients and methods: Thirty-four MBC patients without any prior exposure to chemotherapy entered the study. All patients had measurable disease in at least one site and were assessable for response and toxicity.
Results: Of 34 assessable patients, 12 obtained a complete (one) or partial (11) response to carboplatin, resulting in an overall response rate of 35% (95% confidence interval, 19.8% to 53.5%). The median duration of response was 8 months (range, 2+ to 12 months). Responses were seen in lymph nodes (four of six), lung (five of nine), skin and soft tissues (four of nine), breast (two of eight), and liver (three of 11), but not in measurable lytic lesions of the bone. Toxicity was mild, mainly consisting of emesis (81% of the patients; 66% of the courses), leukopenia of World Health Organization (WHO) grade 1 to 2 (47% of the patients; 18% of the courses), and thrombocytopenia (12% of the patients; 3% of the courses). There were no cases of life-threatening toxicity, although one patient developed grade 4 thrombocytopenia without bleeding. Of 22 patients who did not respond to carboplatin, 18 received salvage therapy with cyclophosphamide, doxorubicin, and fluorouracil (CAF; 15 patients); cyclophosphamide, methotrexate, and fluorouracil (CMF; one patient); or hormones (two patients). Objective responses to CAF and hormonal therapy were seen in 11 of 15 and two of two patients, respectively. The remaining patient did not respond to CMF salvage chemotherapy. Overall, the response rate to either first-line carboplatin or second-line salvage therapy was 73.5% (25 of 34 patients). After a median follow-up time of 22 months, the median survival was 19 months.
Conclusions: Carboplatin is an active drug in MBC patients without previous exposure to chemotherapy. In our study, the use of an experimental drug as first-line single-agent treatment in MBC did not have a negative influence on patient survival, as the majority of the carboplatin nonresponding patients could be salvaged with a conventional therapeutic regimen.