Vinorelbine : an active, non cross-resistant drug in advanced breast cancer. Results from a phase II study

To evaluate efficacy and toxicity of vinorelbine and to investigate its cross-resistance with other current drug treatments for metastatic breast cancer. From July 1992 to December 1993, 57 histologically proven breast cancer patients entered this Phase II study. Patients were stratified according to their status of previous treatment, namely, no prior chemotherapy or relapse more than 12 months since the end of adjuvant chemotherapy (Group A) and other patients (Group B). Fifty three patients were evaluable for response, 27 in Group A and 26 in Group B. All patients were evaluable for toxicity. Vinorelbine was initially administered at the dose of 30 mg/sqm weekly by i.v. infusion in 100 ml of normal saline over 20 minutes. A frequency analysis of drug administration in the first 20 cases revealed two main treatment periodicities, corresponding to one week and to three weeks. Thereafter the drug was administered at 30 mg/sqm on day 1 and 8, every 3 weeks. With the new drug schedule, the mean dose intensity increased from 19.7 to 21.1 mg/sqm per week. Overall, an objective response rate of 47% (95% C.I. 33%-61%) was documented. Four patients achieved complete response (7%, CI: 2%-18%) and 21 partial response (40%, CI: 26%-54%). Fifty nine percent of patients in Group A and 35% in Group B showed objective tumor response. The analysis of response rate in previously treated patients failed to show evidence of cross-resistance with vinorelbine. Main side effects, i.e. neutropenia, local pain, and gastrointestinal and flu-like symptoms, were moderate and short lasting. Vinorelbine has clinically significant activity in metastatic breast cancer, and no cross-resistance with prior anthracyclines and CMF treatments. The drug schedule of 30 mg/sqm iv bolus on day 1 and 8 every 3 weeks was found effective and tolerable.