In February 2000 a study looking at breast cancer and hormone replacement therapy was released and was widely reported in the media. Unfortunately the information was presented in a way that caused patients to overestimate the risk of breast cancer. The information was so confusing and alarming that several physicians called me for my interpretation of the data. I know many patients who discontinued hormone replacement therapy because of this study and I think they might want toreconsider their decision once they have more accurate information.

There have been more than 50 studies before this one that looked at hormone replacement therapy and breast cancer. The information presented in this February 2000 study was not very different from what we already knew. The majority of the studies showed no increased risk of breast cancer with hormone replacement therapy. In the few studies that did show an increased risk, the increase was slight.

The recent study looked at the combination of estrogen and progestin (synthetic progesterone) used in a cyclic fashion. The study suggested that using this combination of hormones in this way could increase the risk of breast cancer as much as 40%. Most of the patients and physicians I talked to misinterpreted the data and thought that the risk of breast cancer was 40 percent per year which meant that taking hormones for two years gave an 80 percent risk of breast cancer.


Let’s look at breast cancer rates. A 50 year-old woman in the menopause not taking any hormone replacement therapy [ HRT] would have a risk of developing breast cancer over the next 20 years of 4.5%. If that same woman took hormone replacement therapy for five years there would be no increased risk of breast cancer. After 10 years of use the risk of breast cancer is raised slightly to 5.1 percent over 20 years, a 0.6% increase. After 15 years of hormone use, the risk of breast cancer is 5.7% or an increase in risk of 1.2%.

As you can see the increased risk of breast cancer due to the hormones is very slight and it is nowhere near as high as people thought the article suggested. To put these figures in perspective let’s look at some other factors that raise the risk of breast cancer. If a woman consumes two alcoholic drinks a day her risk of breast cancer is raised from 4.5% to 7.2% over those 20 years. If a woman is not on a hormone replacement therapy but does not get regular exercise, the risk also was raised from 4.5% to 7.2%. If a woman has a weight gain of 20 kgs……… or more after menopause her risk of breast cancer is doubled from 4.5% to 9 percent over that 20 year period.

There are many factors that affect the breast cancer risk more than hormone replacement therapy. The slight increase in risk of breast cancer on hormones is usually more than offset by the 50 % reduction in heart disease, the 50% reduction in osteoporosis, the 50% reduction in bowel cancer and the similar reduction in Alzheimer’s disease. In addition the majority of women who develop breast cancer have never been on a hormone replacement therapy. 

Now let us go back and discuss the recent study that received so much publicity. When they talked about a 40 % increased risk of breast cancer, what they suggested was that the risk of breast cancer grows from 4.5% to 6.3% with 20 years of use. As you can see the increase is very slight. The study also pointed out that this increased risk applied only to thin women and that heavier women did not have such an increased risk. In addition the hormones and the doses used in the study were very different from my present hormone usage. The doses of hormones in the study were not specified but the doses of estrogen used at that time were higher than we use today. The study also used progestin instead of progesterone and these are very different. A progestin is a synthetic product that has some effects like progesterone but other effects that are very different.

Therefore I feel that the progestins could have a very different effect on breast tissue than real progesterone. It is my practice to use real progesterone for a variety of benefits including its lack of effect on breast tissue. In the study the great majority of the women were taking the hormones intermittently or cyclically whereas I prefer continuous treatment with both the estrogen and progesterone; taking hormones this way may have a very different and more beneficial effect on breast tissue.

Women who have had a hysterectomy take estrogen and do not need progesterone. The recent study suggested that women on estrogen alone did not have as high an increased risk of breast cancer as women on combination therapy.

I hope that this summary has given reassurance to many women who are taking hormone replacement therapy. For anyone who has discontinued therapy or is considering the facts before starting, I hope this information has been useful.