Breast Cancer Hormone Replacement Therapy

The low estrogen production typical in menopausal women can cause them to suffer from hot flashes, vaginal dryness, severe mood swings, arrhythmia, loss of libido and insomnia. In the past, to combat these undesirable symptoms, doctors have prescribed hormone replacement therapy (HRT) to millions of women. During HRT, women take estrogen, progesterone or a combination of both hormones to combat these undesired effects of menopause.

HRT: Cure or Cause?

Doctors initially thought that HRT had several benefits beyond alleviating the symptoms of menopause, including reductions in the risks of developing breast cancer, heart disease, stroke and other serious conditions. Essentially, the medical community thought hormone replacement therapy helped women “stay young,” thus reducing many health risks associated with aging.

The publication of a large HRT study in 2002 changed many doctors’ perceptions of the treatment. The study, which involved healthy post-menopausal women receiving HRT, found that the therapy was actually increasing the risk of breast cancer and heart disease in these women. (Rossouw, et al, 2002).

While these potential side effects of hormone replacement therapy are serious, HRT treatments were also found to reduce the risk of:

  • Colon cancer
  • Hip fracture
  • Rectal cancer
  • Uterine cancer.

As a result, the use of HRT is still controversial and should be carefully considered according to each individual case. Hormone replacement therapies should only be prescribed to patients who are at an extremely low risk of developing any of the negative side effects of this treatment.

HRT and Breast Cancer Risk

According to the American Cancer Society (2009), HRT has now been definitively shown to increase breast cancer risk. The longer a woman partakes of the therapy, the higher her risk will climb. This was confirmed by a 1997 study conducted in Sweden.

During this study, Swedish researchers wanted to observe the effect of HRT on the recurrence of breast cancer in post-menopausal women who had beaten the disease once. Fully expecting to find that HRT reduced the risk of recurrence, they found instead that within two years of beginning the study, women receiving HRT were three times more likely to have a recurrence (National Cancer Institute, 2008). The study was supposed to follow the women for a median of five years, but was discontinued after two years because of the risk to the women.

Fortunately, it has since been found that a woman’s risk of developing breast cancer will return to pre-HRT levels within five years of discontinuing the treatment.

Why Does HRT Increase the Risk of Breast Cancer?

Breast tissue can grow in response to exposure to estrogen, as is most evident during the breast development of young girls entering puberty. In over half the cases of breast cancer, the cells involved retain the hormone receptors of normal breast tissue. When estrogen binds to these receptors, it stimulates rapid growth and reproduction of the cancer cells.


National Cancer Institute. (2008). Hormone replacement therapy and breast cancer relapse. Retrieved October 22, 2010, from

Rossouw, J., Anderson, G., Prentice, R., LaCroix, A., Kooperberg, C., Stefanick, M., et al. (2002). Risks and benefits of estrogen plus progestin in healthy postmenopausal women: principal results From the Women’s Health Initiative randomized controlled trial. Retrieved October 26, 2010, from

The American Cancer Society. (2009). Breast cancer facts and figures 2009-2010. Retrieved October 22, 2010, from