The impact of obesity on prostate cancer recurrence observed after exclusion of diabetics

Purpose: Although overall there is a positive association between obesity and risk of prostate cancer (PrCa) recurrence, results of individual studies are somewhat inconsistent. We investigated whether the failure to exclude diabetics in prior studies could have increased the likelihood of conflicting results. Methods: A total of 610 PrCa patients who underwent radical prostatectomy between 2005 and 2012 were followed for recurrence, defined as a rise in serum PSA ≥ 0.2 ng/ml following surgery. Body mass index (BMI) and history of type 2 diabetes were documented prior to PrCa surgery. The analysis was conducted using Cox proportional hazard models. Results: Obesity (25.6 %) and diabetes (18.7 %) were common in this cohort. There were 87 (14.3 %) recurrence events during a median follow-up of 30.8 months after surgery among the 610 patients. When analyzed among all PrCa patients, no association was observed between BMI/obesity and PrCa recurrence. However, when analysis was limited to non-diabetics, obese men had a 2.27-fold increased risk (95 % CI 1.17–4.41) of PrCa recurrence relative to normal weight men, after adjusting for age and clinical/pathological tumor characteristics. Conclusions: This study found a greater than twofold association between obesity/BMI and PrCa recurrence in non-diabetics. We anticipated these results because the relationship between BMI/obesity and the biologic factors that may underlie the PrCa recurrence–BMI/obesity association, such as insulin, may be altered by the use of anti-diabetes medication or diminished beta-cell insulin production in advanced diabetes. Studies to further assess the molecular factors that explain the BMI/obesity–PrCa recurrence relationship are warranted.