Body mass index and the clinicopathological characteristics of clinically localized renal masses-An international retrospective review

OBJECTIVES: To investigate the potential association between body mass index (BMI) and clinicopathological features of clinically localized renal masses. MATERIALS AND METHODS: An international, multi-institutional retrospective review of patients who underwent surgery for clinically localized renal masses between 2000 and 2010 was undertaken after an institutional review board approval. Patients were divided into 4 absolute BMI groups based on the entire cohort׳s percentiles and 4 relative BMI groups based on their respective population (American or Italian). Renal mass pathological diagnosis, renal cell carcinoma (RCC) subtype, Fuhrman grade (low and high), and clinical stage were compared among groups using Fisher׳s exact test, Kruskal-Wallis test, and the Cochran-Armitage trend test. A multivariate logistic analysis was performed to evaluate independent association between tumor and patient characteristics with tumor pathology (Fuhrman grade). RESULTS: A total of 1,748 patients having a median BMI of 28 (interquartile range 25-32) were evaluated. Benign masses and RCC cases had similar proportion across BMI groups (P = 0.4). The most common RCC subtype was clear cell followed by papillary carcinoma, chromophobe, and other subtypes. Their distribution was comparable across BMI groups (P = 0.7). Similarly, clinical stage distribution was comparable with the overall cohort. The distribution of Fuhrman grade in RCC, however, demonstrated an increased proportions of low grade with increasing BMI (P<0.05). This trend was maintained in subgroups according to gender, stage and age (P<0.05 in all subgroup analysis). In a multivariable model that included potential confounders (i.e., age, sex, and tumor size) higher BMI groups had lower odds of presenting a high Fuhrman grade. CONCLUSION: In this study, higher BMI was associated with lower grade of RCC in clinically localized renal masses. This may, in part, explain better survival rates in patients with higher BMI and may correlate with a possible link between adipose tissue and RCC biology.