Subcutaneous Fat Is Associated with Improved Survival in Patients with Non-Metastatic Clear Cell Renal Cell...

Introduction: The "obesity paradox" describes the observed association between improved cancer-specific (CSS) and overall (OS) survival observed among obese (BMI ≥ 30 kg/m²) patients with RCC. Prior studies have reported lower stage/grade tumors among obese patients to explain this. This study aimed to evaluate subcutaneous (SFA) and visceral fat area (VFA) associations with CSS, OS, tumor stage and grade among patients with non-metastatic clear cell RCC. Methods: Following IRB approval, patients undergoing nephrectomy for clear cell RCC between 2000 and 2023 were screened for inclusion. Eligible patients were those with non-metastatic disease and available preoperative imaging within 90 days of surgery. SFA and VFA were determined using mid-L3 imaging and standardized Hounsfield Unit thresholds. Multivariable Cox models evaluated factors associated with 5-year CSS and OS, and multivariable logistic regression models evaluated associations with pathologic stage (pT) 3-4 and Fuhrman grade 3-4 disease. Results: 400 patients were included. Higher SFA quartiles were independently associated with improved CSS (Q3 HR 0.21, p = 0.029; Q4 HR 0.24, p = 0.042) and OS (Q2-Q4 HR range 0.35-0.52, all p < 0.05) compared to Q1. VFA was not independently associated with OS and showed only an isolated association with CSS in the third quartile (HR 2.95, p = 0.041). Neither SFA nor VFA were independently associated with RCC stage or grade. Conclusions: Greater subcutaneous adiposity was associated with improved 5-year CSS/OS, whereas visceral adiposity did not demonstrate consistent associations with survival outcomes. These findings refine the obesity paradox and reflect the importance of fat distribution as a more specific risk factor than weight-based measures such as BMI alone.