Effect of obesity on histological type of renal tumor: The Uroccr study 69

Renal cell carcinomas (RCC) are increasing worldwide and obesity is one of its recognized causal factor. Obesity thus could be differently associated with the different histologic types of renal tumors and also impact prognosis and patient care.

The primary objective was to evaluate an association between obesity and histological type of RCC. The secondary objective was to assess if there was an effect of obesity on tumor characteristics.

A multicenter comparative descriptive study was carried out in nearly 30 French hospitals. Histological features of operated RCC of patients included between 2007 and 2020 were compared according to their BMI. Obesity was defined as a BMI≥30kg/m², with a P<0.05.

In total, 6749 RCC were analyzed, including 1687 (25%) from obese patients. This population was more frequently diabetic (61% versus 41%, P<0.001) and hypertensive (27% versus 11%, P<0.001). Regarding histological evaluation, the obese group presented clearer cell carcinoma. Other types presented odd ratios below 1 on multivariate analysis, P<0.01 except for type II papillary RCC. Tumor size (pT) and nuclear ISUP grade were both lower when BMI was above 30kg/m²: 72.4% of size pT 1-2 versus 68.5% (P=0.026) and 50% of nuclear ISUP grade 1-2 versus 43.3% for the non-obese group (P<0.0001). There was no difference in survival due to an insufficient number of events.

In this large cohort study, we report novel data on a positive association between obesity and histological type of RCC, in particular clear cell RCC.