California teachers study confirms link between hormone replacement therapy and risk of breast cancer

August 13, 2010

The use of hormone replacement therapy was associated with an increased risk of developing invasive breast cancer in the California Teachers Study, confirming previous findings from the Women's Health Initiative, according to results published in Cancer Epidemiology, Biomarkers, and Prevention.  In the observational study of over 56,000 postmenopausal women, 2,857 developed invasive breast cancer during the average follow-up period of almost ten years.  Women who used combination estrogen/progestin hormone replacement therapy were at the greatest risk of developing breast cancer.

No significant statistical evidence was found that BMI, alcohol intake, parity (childbirth history) or mammography screening within the last two years had an impact on the association.