Germline CAG repeat length of the androgen receptor and time to progression in patients with prostate cancer treated with androgen deprivation therapy

Objectives: • Germline CAG repeat polymorphisms in the androgen receptor (AR-CAG) have been shown to influence the activity of the AR. • The purpose of the present study was to determine if AR-CAG repeat length correlates with time to progression on androgen deprivation therapy (ADT).

Patients and methods: • Germline AR-CAG repeat lengths were determined in a cohort of 480 patients with recurrent or metastatic prostate cancer treated at a single tertiary care institution and correlated to time to progression (TTP) and overall survival.

Results: • There was no significant correlation between differences in the AR-CAG repeat lengths and TTP or overall survival in patients with prostate cancer receiving ADT. • AR-CAG repeat lengths did not significantly correlate with age, prostate-specific antigen (PSA), Gleason score or clinical stage at diagnosis. • In patients with metastatic disease, longer AR-CAG repeat lengths (>23 vs ≤23) were associated with a longer TTP on ADT, but this finding was of borderline significance (median TTP 18.3 vs 15.5 months, P = 0.09; adjusted HR = 0.76, 95% confidence interval = 0.54-1.09).

Conclusions: • This is the largest published study to date investigating the association of germline AR-CAG repeat lengths and efficacy of ADT in prostate cancer. • Germline AR-CAG repeat lengths do not predict response to ADT.