Objectives: Obesity, a significant risk factor for renal cell carcinoma (RCC), has recently become a public health problem in Japan. In addition, the incidence of RCC in Japan has steadily increased during the past few decades. The objective of the present study was to investigate the relationship of body mass index (BMI) to the prognosis of Japanese patients with RCC.
Methods: From January 1991 to December 2002, 270 operations for RCC in 269 consecutive Japanese patients were performed at our institution. BMI data were available for 264 (98%) of the 269 patients. Overall, cancer-specific, and recurrence-free survival were investigated using the Kaplan-Meier method, and the Cox regression model was used to determine the significant prognostic factors on multivariate analysis.
Results: Of the 264 patients, 140 (53.0%), 67 (25.4%), and 57 (21.6%) had a BMI of less than 23, 23 to 25, and greater than 25 kg/m2, respectively. These three BMI groups were not significantly different in age, sex, presenting symptoms, tumor stage, or grade. On univariate analysis, a significant advantage regarding overall and cancer-specific, but not recurrence-free, survival was found for patients with a BMI of 23 kg/m2 or greater compared with those with a BMI of less than 23 kg/m2. Also, on multivariate analysis, the BMI was significantly associated with overall and cancer-specific, but not recurrence-free, survival.
Conclusions: Our findings suggest that a BMI of 23 kg/m2 or more favorably affects the prognosis of Japanese patients with RCC. However, additional studies are needed to verify these results.