A single blood hormone measurement in postmenopausal women can predict the risk of hormone-receptor positive breast cancer for up to 20 years. The findings may be integrated into breast cancer risk prediction models.

Previous research has linked plasma estrogen and androgen levels with risk of postmenopausal breast cancer. However, key questions had remained unanswered. “Most of the previous studies had less than 10 years of follow-up, so we did not know how long the elevated hormones can predict subsequent breast cancer risk,” Xuehong Zhang, MD, epidemiologist at Brigham and Women’s Hospital in Boston, said in an interview with Health Imaging. Researchers also had not determined how associations between hormone levels and risk differed by hormone-receptor status.

Zhang and colleagues sought to answer the questions and conducted a prospective analysis with the Nurses’ Health Study Cohort. They analyzed 796 women diagnosed with postmenopausal breast cancer through June 2010, who had not received hormone therapy at blood collections. Blood hormone levels were measured between 1989 and 1990, and between 2000 and 2002. Each patient was matched with two controls who had not been diagnosed with breast cancer.

The researchers found that women in the top 25 percent of levels of estradiol,  free estradiol, testosterone, free testosterone and dehydroepiandroesterone sulfate (DHEAS) faced a 50 to 107 percent higher risk of breast cancer compared with women in the lowest 25 percent of levels.

Zhang et al reported that relative risks held steady over time and were similar when comparing cases diagnosed one to 10 years vs. 11 to 20 years after blood collection. The findings suggest one blood hormone measurement is associated with breast cancer risk up to 20 years later, said Zhang.

They also found elevated hormone levels, with the exception of DHEAS, were strongly associated with increased risk for hormone-receptor positive breast tumors.

Zhang and his team, along with several other research groups, are considering including the hormones in breast cancer risk prediction models and evaluating whether the addition of blood hormone levels improves the discriminative ability of the models to identify high-risk women who would benefit from enhanced screening or chemoprevention.

The findings are promising but require replication by additional studies, cautioned Zhang, who presented the results Oct. 18 at the American Association for Cancer Research International Conference on Frontiers in Cancer Prevention Research in Anaheim, Calif.