PurposeThis cross-sectional study explored associations of BMI with renal cell carcinoma (RCC) pathological grade and stage, and how these associations vary by BMI-related factors, to better understand the obesity paradox.MethodData was obtained from 2 academic institutions for this cross-sectional study of RCC patients who underwent surgical treatment. Logistic regression models were used to identify BMI-related factors and to estimate odds ratios (ORs) and 95% confidence intervals (CIs) for diagnosis with high grade or advanced stage.ResultsA total of 1949 cases, 1526 from Roswell Park Comprehensive Cancer Center (Roswell Park) and 423 from University of Arizona Baner-University Medical Center Tucson (BUMCT), were included. In both datasets, obesity was significantly associated with lower odds of high grade compared with non-obese (OR 0.69, 95% CI 0.54-0.88 in Roswell Park, OR 0.62, 95% CI 0.41-0.94 in BUMCT). In Roswell Park, unintentional weight loss at the time of surgery was associated with higher odds of high grade (OR 3.81, 95% CI 2.38-6.09) and advanced stage (OR 4.12, 95% CI 2.74-6.20). In both datasets, older age was associated with reduced odds of obesity and higher odds of high grade, and heterogeneous associations between obesity and high grade by age group were observed (PInteraction = 0.001) in Roswell Park. Former smokers had increased odds of obesity in BUMCT and increased odds of high grade in both datasets. In BUMCT, obesity was significantly associated with reduced odds of high grade in patients who never smoked, not in patients who have smoked, but heterogeneity by smoking status was not significant.ConclusionHigher BMI was linked to a lower likelihood of high-risk RCC pathological characteristics consistent with the obesity paradox. However, BMI-related factors, including older age and smoking, were associated with higher odds of RCC severity, potentially modifying the associations between BMI and severity.
Shrivastava et al. (2026) studied this question.