New title: Prospective, multicenter, randomized, independent-group, open-label phase II study to investigate the efficacy, safety and tolerability of 4 regimens with 3 doses of ZK 219477 (16 and 12 mg/m² body surface area as 3-hour infusion or 22 mg/m² body surface area as 30-minute or 3-hour infusion) in patients with metastatic breast cancer. (Old title before amendment:Prospective, multicenter, randomized, parallel-group, open-label phase II study to investigate the efficacy, safety and tolerability of 2 doses of ZK 219477 (16 and 12 mg/m² body surface area) in patients with metastatic breast cancer.)