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 ≥ 5 with at least one score ≥ 12. RESULTS. Compared to men with AR repeat length ≤ 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 ≥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 3α-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.