Impact of body mass index and tumor location on the incidence of benign histology at the time of nephron-sparing surgery.

Purpose: Gender, smoking history, patient age, and tumor size have been found to impact the likelihood of benign histology at the time of nephron-sparing surgery (NSS). Providing external validation of these variables and evaluating the relationship between body mass index (BMI) and tumor location on the likelihood of benign histology during NSS for T1 tumors were the objectives of this study.

Methods: Data were analyzed for consecutive patients undergoing NSS for T1 disease. Central tumors either were completely encircled by renal parenchyma, descended below the cortico-medullary junction, or were in direct opposition to the collecting system, renal sinus, or the hilar structures. Categorical variables were evaluated with chi-square test, and continuous variables were analyzed with independent sample t test. Logistic regression identified independent predictors of final pathology.

Results: NSS was performed in 316 patients, of whom 79 (24 %) had benign tumors. Patients with benign tumors were more likely to be female, to have a lower BMI, and to have peripheral tumors. On multivariate analysis, female gender (hazard ratio, 3.97; 95 % CI, 2.92-4.53, p < 0.001), peripheral tumor location (hazard ratio, 2.27; 95 % CI, 1.73-3.21, p = 0.014), and lower BMI (hazard ratio, 1.5; 95 % CI, 1.12-1.94, p = 0.015) were independently associated with benign histopathology at the time of surgical resection.

Conclusions: Prospectively identifying which T1 tumors are benign would have tremendous implications for the patient. Ours is the first study that has identified the impact of tumor location and BMI on the risk of benign histology. Additional studies are needed to corroborate these findings and incorporate these data into future nomograms.