Chemotherapy dosing only based on body surface area (BSA) results in marked pharmacokinetic and toxicity variations, which may result in an inferior outcome for some patients. A toxicity-based dosing schedule for individually tailored treatment with granulocyte colony-stimulating factor (G-CSF) supported 5-fluorouracil (F), epirubicin (E) and cyclophosphamide (C) (dFEC) was developed and studied in patients with metastatic breast cancer with the purpose to determine its efficiency and toxicity. Twenty-six women, median age 48 years, were included and the individual E and C doses were tailored stepwise based on the recorded hematological toxicity. Twenty-one patients (81%; 95% confidence interval (CI), 66% to 96%) had an objective response, including six complete responses (23%; CI, 7%-39%). At median follow-up of 113 months, the median time to progression and median overall survival were 14 and 36 months, respectively. The delivered dose intensity was high but varied substantially between patients (ranges F 126-202, E 14.4-36.0, C 160-510 mg/m(2)/w). The dominating grade III/IV toxicity was nausea (12% of patients) and febrile neutropenia (31% of patients). The tailored and dose-escalated FEC was highly active and feasible in metastatic breast cancer and may provide a pragmatic way of overcoming the shortcomings of standard BSA-based dosing.