['To evaluate the efficacy and toxicity of single-agent vinorelbine (VNB), a semisynthetic vinca alkaloid, in patients with breast cancer previously treated with other chemotherapeutic regimens for metastatic disease.', 'Sixty-seven of 70 patients with assessable disease entered onto the study were assessable. The main characteristics were as follows: median age, 60 years (range, 41 to 77); median performance status (PS; Karnofsky score), 90 (range, 60 to 100); and number of previous chemotherapeutic regimens given--one in 17, two in 27, three in eight, four in two, and five in one patient. The dominant sites of metastasis were viscera in 40, bone in 16, and soft tissues in 11 patients. VNB was administered beginning with the dose of 20 mg/m2 by 60-minute intravenous (iv) infusion weekly, with a dose escalation up to 25 mg/m2 if the first four courses were well tolerated. The treatment was continued until disease progression.', 'Overall, 845 courses of VNB were given (median, 10; range, eight to 33). Objective responses were as follows: complete response (CR) in three (4.5%), partial response (PR) in 21 (31.2%), stable disease (SD) in 20 (30%), and progressive disease (PD) in 23 patients (34.3%). Twenty-four of 67 assessable patients obtained a major objective response (CR or PR, 36%; 95% confidence interval [Cl], 24% to 47%). Thirty-three percent of patients had a > or = 33% reduction of dose-intensity (DI). The median time to progression was 18 weeks. The drug was active in patients pretreated with either cyclophosphamide, methotrexate, and fluorouracil (CMF) or anthracyclines. The most relevant toxicity observed was myelosuppression: 17 (25%) and 19 patients (28%) had World Health Organization grade III, and six (9%) and six patients (9%) had grade IV leukopenia and granulocytopenia, respectively; two (3%) and two patients (3%) had grade III and IV anemia, respectively. Nonhematologic toxicities were phlebitis (grade II or III in 15 patients), alopecia (grade I or II in 16), nausea and vomiting (grade II or III in 15), diarrhea (grade II in two), constipation (grade II or III in 16), stomatitis (grade II or III in 13), peripheral neuropathy (grade II in seven), and asthenia (grade II in five).'] Is vinorelbine an active antiproliferative agent in pretreated advanced breast cancer patients : a phase II study?