The polymorphism of CAG repeats in the androgen receptor gene and breast cancer mortality

BACKGROUND: The polymorphic CAG repeats of the androgen receptor (AR) gene have been suggested to affect the risk of breast cancer, but the results are controversial. In addition, the relationship between patients' CAG genotype and the prognosis has not been investigated. OBJECTIVE: The purpose of this study is to access the association between the polymorphic CAG repeats and the incidence and prognosis of breast cancer. METHODS: One hundred and fifty-six breast cancer cases and 108 healthy controls from Taipei Veteran General Hospital were enrolled. The length of CAG repeats was analyzed among by means of PCR amplification. The logistic regression model was used for cross-sectional analyses of prevalent breast cancer. Furthermore, we categorized the cases according to the average length of both CAG alleles (CAGn >= 23 versus <23). Outcomes were disease-free survival and mortality. The Cox proportional hazards model and Kaplan-Meier estimate were used for survival analysis. RESULTS: The median age was 56 (51-64) and 46 (37-52) in breast cancer patients and healthy controls, respectively. The median of CAGn was 22.5 (21.5-24) in study group and 23 (21.5-24) in controls. Our study showed the length of CAG repeats did not contribute to breast cancer or benign breast tumors (HR 1.01; 95% CI, 0.90-1.13). In the median follow-up of 6.59 years, we found the CAGn >= 23 (n = 75) could be a poor prognosis (adjust HR, 3.08; 95% CI, 1.42-6.67, p = 0.004). CONCLUSION: The CAG polymorphism is not associated with development of breast cancer, but patients with more CAG repeats of the AR gene are prone to poor prognoses.