Obesity as a Risk Factor for Unfavorable Disease in Men with Low Risk Prostate Cancer and its Relationship with Anatomical Location of Tumor

Purpose We investigated the influence of obesity on unfavorable disease in men with low risk prostate cancer eligible for active surveillance and verified the underlying relationship with tumor location. Materials and Methods We analyzed the records of 890 patients with biopsy Gleason score 6 who underwent radical prostatectomy for prostate cancer via multicore (12 or more) biopsy at our institution. Unfavorable disease was defined as primary Gleason pattern 4 or greater, or pathological stage T3 or greater. Multivariate logistic regression analysis was performed to identify factors associated with unfavorable disease. The association of unfavorable disease with anatomical location of the index tumor was assessed. Results Overall 216 (24.3%), 544 (61.1%) and 130 men (14.6%) had a body mass index of less than 23 (normal), 23 to 27.5 (overweight) and 27.5 kg/m² or greater (obese), respectively, according to established cutoff points for Asian men. Multivariate analysis showed that age, prostate volume and body mass index were independent factors for predicting unfavorable disease regardless of the various active surveillance criteria used. For Johns Hopkins Hospital criteria the risk of unfavorable disease was higher in obese patients than in normal weight patients (OR 3.30, p = 0.022). Unfavorable disease was more frequent in cases of transition zone cancer than nontransition zone cancer across all criteria for active surveillance (all p <0.01). Among men fulfilling Johns Hopkins Hospital criteria the proportion of transition zone cancer was 4.2% for normal weight, 11.6% for overweight and 16.7% for obesity, respectively (p = 0.022). Conclusions Obese men with low risk prostate cancer who are eligible for active surveillance are at higher risk for unfavorable pathological features. Obese men more frequently had transition zone cancer, which was associated with unfavorable pathology findings in those with very low risk prostate cancer.