Androgen receptor CAG repeat length is not associated with the risk of incident symptomatic benign prostatic hyperplasia: results from the Prostate Cancer Prevention Trial.

Background: To examine whether androgen receptor (AR) CAG repeat length was associated with the risk of incident benign prostatic hyperplasia (BPH).

Methods: A nested case-control study of 416 BPH cases and 527 controls drawn from Prostate Cancer Prevention Trial placebo-arm participants who were free of BPH at baseline. BPH was assessed over 7 years and was defined as receipt of medical or surgical treatment, two scores > 14 on the International Prostate Symptom Score (IPSS), or two increases in IPSS > or = 5 with at least one score > or = 12.

Results: Compared to men with AR repeat length < or = 19, the covariate-adjusted odds ratios [95% CI] were 1.07 [0.73, 1.57] and 0.90 [0.55, 1.45]) for repeat length 20-24 and > or =25, respectively. There was a weak association of AR repeat length with baseline serum testosterone (T) (Spearman r = 0.09, p < 0.02); however, control for or stratification by T did not change study results. Further, results did not differ when stratified by body mass index or baseline concentration of 3alpha-diol glucoronide, and were similar for all BPH definitions.

Conclusions: There were no associations of AR CAG repeat length and BPH risk. Knowledge of AR CAG repeat length provides no clinical useful information for the prevention of symptomatic BPH.