Less Hormone Therapy Use Linked to Less Breast Cancer Risk
Research suggests that the decline in hormone therapy during postmenopause is a key reason for the decline seen in a known risk factor for breast cancer. Atypical ductal hyperplasia is associated with a three- to fivefold increased risk of developing breast cancer.
Ever since the release of the results of the Women’s Health Initiative studies, which were conducted in the 1990s, there has been a reduction in the use of hormone replacement therapy by women. The estrogen plus progesterone study found an increased risk of breast cancer, stroke, heart attack, and blood clots associated with taking the combination therapy, while women who took estrogen alone were found to be at increased risk of stroke and venous thrombosis (blood clots usually in deep vein in the legs). Specifically, postmenopausal hormone treatment is associated with a greater risk of benign breast biopsies as well as early and late stages of breast cancer and atypical ductal hyperplasia.
Atypical ductal hyperplasia, according to Mayo Clinic, forms when breast cells in the milk ducts become abnormal in size, shape, number, appearance, and growth pattern. If the abnormal cells continue to grow and are not treated, they may become invasive breast cancer.
It now appears that the decline in the use of postmenopausal hormone therapy is associated with a new benefit, a decline in the rate of atypical ductal hyperplasia. Researchers used data from the Breast Cancer Surveillance Consortium and examined the rates of atypical ductal hyperplasia to identify risk factors and rates for more than 2.4 million mammograms.
The investigators found that use of postmenopausal hormone therapy declined from 35 percent to 11 percent between 1996 and 2005, while atypical ductal hyperplasia decreased from 5.5 per 10,000 mammograms in 1999 to 2.4 in 2005. The rates of breast cancer with atypical ductal hyperplasia peaked at 4.3 per 10,000 mammograms in 2003, but then declined to 3.3 in 2005. The investigators had not expected to see a decline in the rate of atypical ductal hyperplasia with a decline in postmenopausal hormone treatment use.
The researchers also found that when women are diagnosed with atypical ductal hyperplasia with associated breast cancer, the cancer tends to be low-grade or at an early stage. All of the findings in this study may help researchers identify the different ways breast cancer develops and the role that postmenopausal hormone treatment plays in increasing the risk for and rate of breast cancer.
Menes TS et al. Cancer Epidemiology Biomarkers and Prevention 2009 Nov; 18:2822-28