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More Research Finds Breast Cancer Risk Associated with Long-Term Hormone Replacement Therapy

Another study highlights potential risks associated the long-term use of hormone replacement therapy (HRT), adding to a growing body of research. The latest study showed that taking estrogen for 15 years or longer increased a woman´s breast cancer risk by 19 percent, compared to women who never used the treatment, and the risk was increased to up to 83% for women who took a combined estrogen and progestin regimen. Furthermore, the risk was highest among women who had lower body mass indexes. Researchers of this study concluded that hormone replacement therapy should be used for the shortest amount of time possible in those women who need it to relieve menopausal symptoms.

HRT is synthetic estrogen and progesterone (progestin) designed to "replace" a woman's depleting hormone levels. HRT has been shown to be highly effective at relieving menopausal symptoms and may provide protection against conditions such as osteoporosis. However, a growing body of research shows a potential link between HRT and an increased risk for breast cancer, as well as an increased risk of ovarian cancer (with long-term use) and cancer of the uterine lining (in women who do not take progestin with estrogen). With respect to the association between HRT and breast cancer, research has revealed differences based on individual characteristics such as age and the type of HRT used.

For the current study, researchers from the University of Southern California analyzed medical records of about 3,000 women over a 10-year period, from about 1995 to 2006. The researchers found that, for 15 years or longer, women taking estrogen increased their risk of breast cancer by 19 percent, compared with women who had never used HRT. Using a combined estrogen/progestin therapy for this length of time increased the risk by up to 83 percent. Those women taking the combined therapy without any interruption had highest risk. Moreover, women with body-mass indexes lower than 30, which is the level considered to be obese, were at a higher risk of breast cancer than obese women.

The link between HRT and breast cancer remains controversial. Some studies have shown the risks of breast cancer to be minimal among women who use HRT while other studies have shown a more significant risk. Although studies have been inconsistent, there appears to be an emerging consensus that HRT, particularly its long-term use, may increase the risk for breast cancer. The National Institutes of Health acknowledges the health risks of HRT but also recognize the benefits for some women with severe menopausal systems. Thus, the decision whether or not to take HRT remains an individual one that a women should weigh carefully with her physician based on her own medical situation.

Additional Resources and References

·         The study, “Menopausal Hormone Therapy and Subsequent Risk of Specific Invasive Breast Cancer Subtypes in the California Teachers Study,” was published in the August 10, 2010 issue of Cancer Epidemiology, Biomarkers & Prevention,

·         For more information on HRT, visit