These findings indicate that the benefit of anastrozole in reducing the risk of developing breast cancer during this follow-up period was approximately 50% for the 75% of women whose E2/SHBG was in the top three quartiles, At this stage it is unclear if risk for the highest quartile of E2/SHBG is higher than for the second or third quartile, or if the there is a risk threshold somewhere in or near the second quartile of E2/SHBG. The gene discussed is SHBG; the disease is breast cancer.