Phase II study of second-line treatment with high-dose cyclophosphamide in recurrent metastatic breast cancer.

A total of 78 patients with second recurrence or progression of histologically verified breast cancer were treated with single-agent cyclophosphamide given at 2.5 g/m2 by i.v. infusion every 3 weeks along with mesna support. All had previously been treated with epirubicin and cisplatin or epirubicin alone. Toxicity was predominantly hematologic: WHO grade III+IV toxicity was found in 95% of cases. The overall response rate was 26.7% (95% confidence limits, 15.8-41.4%), with 7% of patients achieving a complete response (CR) and 19.7%, a partial response (PR). The median duration of CRs and PRs was 11 and 5 moths, respectively. The response rate observed for patients previously treated with epirubicin alone was 30.5% in contrast to the 8.3% recorded for patients previously treated with cisplatin plus epirubicin. Thus, an indication of cross-resistance was absent between cyclophosphamide and epirubicin but possible between cyclophosphamide and cisplatin.