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Estrogen and Breast Cancer

What is the real story?  Does taking hormone replacement cause breast cancer?  That is the story so many women have heard from their own doctors.  It must be true.  The anxiety spread to woman facing menopause started from the Women’s Health Initiative Study in 2002.  This was one of the largest studies done with three different categories studied; women who take no hormones, women on “estrogen” only and women who take “estrogen” and progesterone together. Quotation marks are present to indicate that the hormones used were not structurally like our own hormones but were identical for the estrogen produced in horses!  There were 10,000 person-years allotted to each category.  Let’s simplify the statistics and just say 10,000 people per category.  The study was discontinued at 5.2 years with the following conclusions:

                           RATE OF BREAST CANCER CASES PER 10,000

No Hormones Premarin Only Premarin and Provera
     
30 LESS THAN 30 38
     

The results show an increase of 8 cases more for the prem/pro (or estrogen/progesterone) group than the women taking no hormones.  The increase is 8/10,000.  When I tell my patients this; I remind them that this is less than one case per 1,000 !  The study itself concluded that the increased breast cancer cases were of nominal statistical significance.  What that means is that there was an increase but very little.  Both of these hormones stimulate breast tissue.  Is it really surprising to find an increase in breast cancer if woman take these hormones every day?  Let’s look at the estrogen alone group.  They actually had less breast cancer than the no hormone group!  These trends remained in follow-up studies 8 years after the initial study and a most recent follow-up of 13 years afterwards. 

Hormone replacement therapy can help woman prevent heart disease, Alzheimer’s disease and other dementias, osteoporosis, can help prevent colon cancer.  It helps facilitate mental function (especially memory), sexual function, and helps prevent anxiety and depression.

The increased risk of breast cancer is very small in comparison to the benefits.  It is particularly interesting that in the estrogen therapy alone group, there was a decrease in breast cancer cases in comparison to woman who did not take any hormones.  This was not a fluke as the ratios persisted in two follow-up studies!  So, woman who have had hysterectomies and do not need the progesterone component of hormone therapy are at even less risk for breast cancer than women who take no hormones.

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