The association of body mass index with tumor aggression among men undergoing radical prostatectomy

•Increased BMI is associated with adverse pathology in peripheral zone tumors, but not in the transition zone.•Among patients with Grade Group 1 or 2 disease, increasing BMI was associated with the presence of pT3a or higher transition zone tumors.•Among patients with Grade Group 3 or higher disease, increasing BMI was not associated with the presence of aggressive transition zone or peripheral zone tumors. To evaluate the association of preoperative body mass index (BMI) on adverse pathology in peripheral (PZ) and transition zone (TZ) tumors at time of prostatectomy for localized prostate cancer. Clinical and pathologic characteristics were obtained from up to 100 consecutive prostatectomy patients from 10 prostate surgeons. BMI groups included normal (18.5–24.9), overweight (25–29.9) and obese (> 29.9). “Aggressive” pathology was defined as the presence of Grade Group (GG) 3 or higher and/or pT3a or higher. Pathologic characteristics were evaluated for association with BMI using univariate analyses. Our primary outcome was the association of BMI with adverse pathology, which was assessed using logistic regression accounting for patient age. We hypothesized that obese BMI would be associated with aggressive TZ tumor. Among 923 patients, 140 (15%) were classified as “normal” BMI, 413 (45%) were “overweight”, and 370 (40%) were “obese.” 474 patients (51%) had aggressive PZ tumors while 102 (11%) had aggressive TZ tumors. “Obese” BMI was not associated with aggressive TZ tumor compared to normal weight. Increasing BMI group was associated with overall increased risk of aggressive PZ tumor (HR 1.56 [95CI 1.04–2.34]; P = 0.03). Among patients with GG1 or GG2, increasing BMI was associated with presence of pT3a or higher TZ tumor (P = 0.03). Increased BMI is associated with adverse pathology in PZ tumors. TZ adverse pathology risk may be increased among obese men with GG1 or GG2 disease, which has implications for future studies assessing behavioral change among men whose tumors are actively monitored.