Distinct effect of body mass index by sex as a prognostic factor in localized renal cell carcinoma treated with nephrectomy ~ data from a multi-institutional study in Japan ~

Background: We assessed the prognostic value of body mass index (BMI) in Asian patients with localized RCC who underwent nephrectomy. Methods: A total of 665 patients who underwent nephrectomy for localized RCC were enrolled in the present study and divided into the two BMI groups: i.e., BMI < 25 in 463 (69.6%) and BMI > 25 in 202 (30.4%) patients. Results: In total, there were 482 (72.5%) males and 183 (27.5%) females. Five-year cancer-specific survival (CSS) rates were significantly higher in increased BMI than the lower BMI group (97.1 and 92.5%: P = 0.007). When stratified by sex, significantly longer CSS in higher BMI was confirmed in males (5-year CSS of 92.7% in BMI < 25 and 98.1% in BMI > 25, p = 0.005), while there was no difference in CSS between BMI groups for female patients. Multivariable analysis exhibited that higher BMI was an independent predictor for favorable CSS in male (cox model: p = 0.041, Fine & Gray regression model: p = 0.014), but not in the female. Subgroup analysis for CSS revealed that favorable CSS with higher BMI was observed in patient subgroups of age < 65 (p = 0.019), clear cell histology (p = 0.018), and tumor size > 4 cm, p = 0.020) as well as male (p = 0.020). Conclusion: Our findings collected from the multi-institutional Japanese dataset demonstrated longer survival in patients with higher BMI than lower BMI for non-metastatic RCC treated with nephrectomy. Intriguingly, this finding was restricted to males, but not to females.