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Background: Although obesity has been associated with larger prostate volumes (PV), few studies have actually investigated whether obesity enhances PV growth, especially among men using 5α-reductase inhibitors., Objective: To examine whether obesity is associated with enhanced PV growth measured by serial transrectal ultrasound (TRUS) measurements., Design, Setting, and Participants: We conducted a secondary analysis of the REduction by DUtasteride of prostate Cancer Events (REDUCE) trial, which was originally aimed at cancer risk reduction among high-risk men with a single negative prestudy biopsy., Intervention: Per-protocol randomization to placebo or dutasteride and mandatory TRUS-guided biopsies at 2 yr and 4 yr., Outcome Measurements and Statistical Analysis: Percentage change in PV at 2 yr and 4 yr from baseline. We tested its association with baseline body mass index (BMI) groups of <25, 25-29.9, and ≥ 30 kg/m(2) using multivariable linear regression. Secondarily, we tested whether BMI was associated with the likelihood of having no PV reduction among men randomized to dutasteride using multivariable logistic regression., Results and Limitations: Of 8122 participants, we analyzed 71.8% and 54.5% with complete 2-yr and 4-yr PV data, respectively. In multivariable analysis, men on placebo with BMI ≥ 30 versus < 25 kg/m(2) had enhanced PV growth from baseline (at 2 yr: 17.0% vs 10.7%, p<0.001; at 4 yr: 29.4% vs 20.1%; p=0.001). Men on dutasteride with BMI ≥ 30 versus < 25 kg/m(2) had attenuated PV reduction from baseline (at 2 yr: -14.3% vs -18.5%; p=0.002; at 4 yr: -13.2% vs -19.3%; p=0.001) and higher likelihood of having no PV reduction (at 2 yr: odds ratio [OR]: 1.44; 95% confidence interval [CI], 1.08-1.93; p=0.014; at 4 yr: OR: 1.62; 95% CI, 1.18-2.22; p=0.003). We found no significant interactions between BMI and dutasteride on PV change at 2 yr and 4 yr (p interaction ≥ 0.36). No clinical outcomes or effects of weight change were assessed., Conclusions: Obesity enhanced PV growth and attenuated PV reduction by dutasteride. The null interaction between obesity and dutasteride for PV change implies that the effect of obesity on dutasteride-treated men is likely a combination of dutasteride-driven PV reduction with obesity-driven PV growth rather than decreased dutasteride efficacy., (Copyright © 2013 European Association of Urology. All rights reserved.)

Background: Findings of studies on the association between androgens and prostate cancer (PCa) are mixed. Androgens may affect prostate-specific antigen (PSA) levels, thereby influencing biopsy recommendations. Also, androgens may stimulate prostate growth at very low levels with no additional effects at higher levels (saturation model)., Objective: To test whether androgens were associated with PCa risk in the placebo arm of a prospective study in which biopsies were performed regardless of PSA level., Design, Setting, and Participants: Of 8122 men in the Reduction by Dutasteride of Prostate Cancer Events (REDUCE) trial, 4073 men (50.1%) received placebo. Key entry criteria were PSA 2.5-10 ng/ml and one prior negative biopsy., Intervention: Per-protocol biopsies at 2 and 4 yr; for-cause biopsies at physician discretion., Outcome Measurements and Statistical Analysis: Multivariable logistic regression was used to test the association between baseline log-transformed testosterone and dihydrotestosterone (DHT) levels and the risk of detecting either PCa or low-grade PCa (Gleason score <6) compared with high-grade PCa (Gleason score >7). In secondary analysis, we stratified the analysis by low baseline androgen levels (testosterone <10 nmol/l; DHT <0.76 nmol/l) compared with normal baseline androgen levels., Results and Limitations: Of 4073 men, 3255 (79.9%) had at least one biopsy after randomization and were analyzed. Androgen levels tested continuously or by quintiles were generally unrelated to PCa detection or grade. PCa detection was similar among men with low compared with normal baseline testosterone levels (25.5% and 25.1%; p=0.831). In secondary analysis, higher testosterone levels at baseline were associated with higher PCa detection (odds ratio: 1.23; 95% confidence interval, 1.06-1.43; p=0.006) only if men had low baseline testosterone (<10nmol/l). For men with normal baseline testosterone (≥10 nmol/l), higher testosterone levels at baseline were unrelated to PCa risk (p=0.33). No association was found for DHT and PCa (all p>0.85)., Conclusions: Baseline serum testosterone and DHT levels were unrelated to PCa detection or grade. Our findings of the lowest testosterone levels being associated with the lowest PCa risk with no further changes with higher testosterone support a saturation model but must be confirmed in future studies using an a priori defined hypothesis. CLINICALTRIALS.GOV IDENTIFIER: NCT00056407., (Copyright © 2012 European Association of Urology. All rights reserved.)