OBJECTIVES: Chemotherapy resistance of renal cell carcinoma (RCC) has been attributed in large part to multidrug resistance (MDR). Reported MDR-modulated chemotherapy for RCC, however, has resulted in only marginal response benefits. In this study, the MDR-modulated effect of paired tamoxifen and colchicine on vinblastine and the possible additive effect of 5-fluorouracil (5-FU) were investigated in the treatment of advanced RCC. METHODS: Chemotherapy was administered every 4 weeks with biweekly vinblastine (4 mg/m(2)/day, intravenously on days 1 and 15) modulated by oral tamoxifen (100 mg/day) and colchicine (1 mg/day) from days -1 to 2 and from days 13 to 16. 5-FU (800 mg/m(2)/day from days 2 to 5) was administered after vinblastine administration as a continuous infusion. RESULTS: Of 17 eligible patients with advanced RCC available for evaluation, 1 achieved a complete response (CR) and 3 a partial response (PR), with an overall response (CR plus PR) rate of 23.5%. The median overall survival time of all patients was 10 months (95% confidence interval [CI] 3.5 to 16.5); that of our patients with poor, intermediate, and favorable risks as stratified by Motzer’s model was 6 (95% CI 1.7 to 10.3), 10 (95% CI 7.9 to 12.2), and 26 (95% CI 24.4 to 27.6) months, respectively. These results are encouraging in view of the poor efficacy of chemotherapy in RCC observed previously. Additionally, the treatment toxicity was limited: toxicity of grade 3 or greater occurred in only 1 patient with leukopenia, and no treatment-related mortality was found. CONCLUSIONS: The encouraging response rates and overall survival with limited toxicity warrant further investigation of this combination therapy as an integrated part of immunochemotherapy for RCC.