Obesity is well known for its role in adverse health effects and mortality [1]. However, obesity is increasingly recognized for its association with prostate cancer development [2] and postdiagnostic outcomes [3], [4], [5]. This includes men undergoing radical prostatectomy for localized prostate cancer, as obesity is associated with increased risk of adverse pathologic outcomes at the time of surgery [4,6].

Obesity increases systemic inflammation and multiple investigations have demonstrated that obesity-related paracrine signaling between the fat surrounding the prostate and prostatic epithelial compartment can lead to tumor progression [7], [8], [9] Periprostatic fat has characteristics of visceral adiposity, is present overlying the anterior prostate, and has been shown by our group to be associated with risk of Grade Group (GG) progression among men on active surveillance for localized disease [10]. Periprostatic fat thickness is associated with increased BMI [11], and a study of Japanese men with GG1 prostate cancer undergoing radical prostatectomy demonstrated that increasing BMI was associated with risk of transition zone tumor presence and adverse pathology [12].

Identification of patient subgroups at increased risk of prostate cancer progression, such as obese men with transition zone tumors, would have implications for patient counseling, management, and, most importantly, future clinical trials evaluating behavioral interventions designed to induce weight loss. We therefore aimed to evaluate the association between BMI and transition zone (and peripheral zone) adverse pathology among a large cohort of men undergoing radical prostatectomy for localized prostate cancer. We hypothesized that increased BMI is associated with risk of GG3 or higher or > pT2 disease among transition zone tumors.