Breast Cancer and Hormone Therapy

The facts and the fiction...there are a lot of both. I, for one, am ready for the media to stop replaying various takes on the Women's Health Initiative (WHI) and alarming women with often erroneous, frequently skewed, stories based on that flawed study. The WHI released in 2002 investigated mostly older women (average age 64) who started hormone therapy (HT), specifically the synthetic hormones, conjugated equine estrogen and medroxyprogesterone ten years or more after menopause and had various medical conditions.

Now we have a story from the Associated Press stating that women who took menopause hormones for 5 years doubled their risk of breast cause and representing this data to be from a new study. The data is from the WHI and was recently reported at the San Antonio Breast Cancer Symposium (Star Tribune, Minneapolis MN, 12/14/08). Nothing new about it.

Noting that HT is most often prescribed for symptomatic women around the years of menopause, the data from a subgroup of WHI participants who were of greatest clinical interest because they represent this typical population, women aged 50-59, was re-analyzed. These women had been on estrogen alone and, compared with those who received placebo, had a 37% reduction in coronary heart disease, an 11% reduction in stroke, an 18% reduction in invasive breast cancer, a 31% reduction in colorectal cancer, a 12% reduction in diabetes, a 10% reduction in total fractures and a 29% reduction in total mortality. (Altman, A. Women's Health Care, 7(10), Fall 2008). A well-respected expert in the field of menopause and associate clinical professor at Harvard Medical School, Dr. Altman explains: the WHI results differ from a number of previous observational studies because it was much shorter than the typical observational study.

"Women in observational studies use HT for a much longer period of time...and continued use of HT is important for prevention" and detecting evidence of that prevention.
The absolute risk of breast cancer with the conventionally-used HT (conjugated equine estrogen and synthetic progestin) is very low, approximately 20 cases more than what would be expected per 10,000 women over 5 years. It is important to note here that many well-designed studies do not show any increased risk of breast cancer with hormone use. (Northrup, C., The Wisdom of Menopause, Bantam Books, 2006).

Despite the mounting evidence that estrogen therapy used in the appropriate population of women is not associated with an increased risk of breast cancer, the addition of a progestogen does appear to slightly increase this risk. One reason that I remain baffled why medroxyprogesterone (Provera) is still on the market and continues to be the most frequently prescribed progestogen! These studies did not include the investigation of bioidentical (human-identical) micronized progesterone. Various progestogens definitely have important differences. Therefore, the arm of the WHI that used the combination including medroxyprogesterone cannot be generalized to hormone therapy that uses the bioidentical form of the medication. In a recent editorial, Barbieri noted the practice-altering, growing body of evidence that hormone therapy using progesterone may be associated with a lower risk of breast cancer than regimens containing other progestogens." (Barbieri RL. OBG Management. 20(8), Editorial.