['The aim of this study is to investigate the prognostic relevance of the best objective response of metastatic target lesions during sunitinib treatment in patients with metastatic renal cell carcinoma.', 'Radiographic analysis of the best objective response according to the Response Evaluation Criteria in Solid Tumors was assessed in 50 patients. Clinicopathological characteristics including the Heng risk classification and sunitinib-related adverse reactions were compared among four patient subgroups [complete response or partial response (CR/PR), stable disease (SD), progressive disease (PD), and those without treatment evaluation (NE)]. Kaplan-Meier and Cox proportional regression analyses of progression-free survival and overall survival were performed to identify prognostic variables.', 'The best objective response was CR/PR in 12 (24\xa0%) patients, SD in 22 (44\xa0%), PD in 6 (12\xa0%), and NE in 10\xa0(20\xa0%). The incidence of hypertension and hypothyroidism was associated with a better objective response. Progression-free survival was 15.0, 9.2, 6.8, and 2.2\xa0months in the CR/PR, SD, PD, and NE groups, respectively (P\xa0=\xa00.0004, log-rank test), while the corresponding median overall survival was 59.7, 24.2, 17.1, and 18.1\xa0months, respectively (P\xa0=\xa00.007). Multivariate analysis revealed that hazard ratios for risk of death of the SD, PD, and NE groups were 4.51 (P\xa0=\xa00.06), 7.93 (P\xa0=\xa00.02), and 4.88 (P\xa0=\xa00.04), respectively, as compared to the CR/PR group.'] Are the best objective response of target lesions and the incidence of treatment-related hypertension associated with the survival of patients with metastatic renal cell carcinoma treated with sunitinib : a Japanese retrospective study?