21-Day oral etoposide for metastatic breast cancer: A phase II study and review of the literature

Previous studies of etoposide for metastatic breast cancer commonly used bolus regimens given over a short period of time and included heavily pretreated patients. Results were poor. Chronic oral regimens would be expected to be superior to bolus doses based on pharmacologic studies and patients with less previous chemotherapy would be expected to have higher response rates. We studied the efficacy of oral etoposide at a dose of 50 mg/m2/day for 21 days of a 28-day cycle in good-risk patients with metastatic breast cancer. Healthy patients (Eastern Cooperative Oncology Group performance status 0, 1, or 2) who had not received chemotherapy for at least 1 year before study entry were selected for therapy. Thirty-four patients were entered; three patients were ineligible and one was cancelled. Thirty patients were available for analysis of response. One complete response and eight partial responses were documented (response rate, 30%; 95% confidence interval, 15-49%). A higher response rate was observed in those patients who never received chemotherapy compared with those who had received prior chemotherapy (57 vs. 6%, p = 0.004). There were two treatment-related deaths, both owing to myelosuppression and infection. We found long-term administration of oral etoposide to have a reasonable response rate for metastatic breast cancer (30%). Our response rate was comparable to those of other published studies of long-term oral etoposide regimens for metastatic breast cancer. Response rates in single-arm studies have generally been higher for long-term oral regimens than those for bolus regimens. We also found the regimen to be significantly toxic, an observation that may be underemphasized in the earlier literature.