Association of body mass index with clinicopathological features among patients with clear cell renal cell carcinoma treated with surgery: a retrospective study

To investigate the potential association between body mass index (BMI) and the clinicopathological features of patients with clear cell renal cell carcinoma (ccRCC). We retrospectively analyzed data from 2541 patients who underwent partial or radical nephrectomy for renal masses between 2013 and 2023 in a single institution. Patients were divided into normal-weight, overweight, and obese groups based on the Chinese BMI classification. Clinicopathological features, including pathologic tumor size, pathologic T (pT) stage, Fuhrman grade or WHO/ISUP grade, renal capsular invasion, perirenal fat or renal sinus fat invasion, and vein cancerous embolus were compared among the groups using Student's t-test or one-way ANOVA for normally distributed continuous variables, and the chi-square or Fisher's test for categorical variables. A total of 2541 ccRCC patients having a median BMI of 24.9 (interquartile range 22.7-27.0) were evaluated. No significant association was found between the pathological tumor diameter and BMI among the normal-weight, overweight, and obese groups (normal-weight vs. overweight, p = 0.31; normal-weight vs. obese, p = 0.21). There was no statistical difference in pT stage (normal-weight vs. overweight, p = 0.28; normal-weight vs. obese, p = 0.23). No statistically significant difference was observed in the distribution of Fuhrman/ISUP grade (p = 0.12), proportion of patients with renal capsular invasion (p = 0.49), perirenal fat or renal sinus fat invasion (p = 1.00), and vein cancerous embolus (p = 0.11) between the normal-weight and overweight groups. However, patients in the obese group tended to have low Fuhrman or WHO/ISUP grades (p < 0.001), and decreased rates of renal capsular invasion (p < 0.05), perirenal fat or renal sinus fat invasion (p < 0.05), and vein cancerous embolus (p < 0.05). Obesity was associated with less aggressive pathological features such as low tumor nuclear grade, low rate of renal capsular invasion, perirenal fat or renal sinus fat invasion, and vein cancerous embolus. This finding may provide clinicopathological evidence and explanations for the "obesity paradox" of RCC.