This Hormone DOES Cause Cancer
Last month I got a call no doctor wants to get.
My patient Helen (never real names of my patients) told me she was diagnosed with breast cancer.
It is possible to be lucky with cancer, and we think this is the case for her.
Early stage, caught on a mammogram, but still no less scary.
Now she is in her late 50’s. She went through menopause in her mid-40’s (a pretty young age). She was on hormone replacement therapy (HRT) for about 10 years, went off for a while, didn’t feel great, and started working with me just last Fall to go back on hormone therapy. We were just getting her “back in the saddle” of feeling good.
Here is the twist.
Those first 10 years she was on HRT, the hormones were not bioidentical. In particular, it was the progesterone that was the synthetic form, called a progestin.
My focus today is this NON-BIOIDENTICAL hormone, a synthetic imitation of one of the main female hormones, that has been repeatedly linked to an increased risk of breast cancer.
Bioidentical progesterone vs. synthetic progestin
This is a fine point of female hormone therapy, but it actually makes all the difference in the risk of using hormone therapy on the risk of developing breast cancer.
Before 1990, many women in menopause were treated with the only estrogen – this main female hormone was called “the fountain of youth”. This changed when doctors realized that without the other major female hormone, progesterone, to balance the estrogen, women were developing endometrial cancer.
Because of what was pharmaceutically available at the time, women on estrogen were then also given a synthetic progestin, and the increase in the risk of endometrial cancer literally went away.
In 1995, one of the first large studies was published looking at the risk of breast cancer in women on estrogen and progestin HRT. Just over 500 women who developed breast cancer were compared to just under 500 women, matched for the same ages and demographics, who did not develop breast cancer.
This study did find that a history of hormone therapy use was not associated with an increased risk of developing breast cancer.
This study was limited by being a historical (retrospective) design, where recall can be incomplete, and the numbers of participants in each group were somewhat small.
In 2002, a study began publishing findings that drew instant media attention to a connection between HRT and breast cancer. This was the Women’s Health Initiative Study (WHI).
This study was conducted by the NIH, with the assistance of Wyeth-Ayerst, the pharmaceutical manufacturer of the hormones used in the study. The WHI study was launched in 1991 and consisted of both clinical trials and observational studies of 161, 808 women.
The clinical trial of interest to us today is the estrogen-plus-progestin vs. placebo study within the WHI. 16,608 postmenopausal women were enrolled in this trial.
In 2002, the WHI stopped the arm of the study that had women on Premarin (oral horse urine estrogen) and Provera (synthetic progestin given as standard hormone combination with estrogen) because it was determined that the women in the hormone group were having a 26% greater chance of developing breast cancer as compared to the women getting the placebos.
(Also, the hormone group was not showing the anticipated cardiovascular benefits of hormone therapy that had been observed in previous studies.)
Here is what we now conclusively know: that the elevated risk of breast cancer in the women on the Premarin and Provera was due to the Provera.
Among other study findings, the women only on the estrogen were continued in the WHI, and 3 years later were found to have a LOWER risk of breast cancer than their counterparts receiving the placebo. The media made extremely little mention of this at the time. There are many doctors around now who are not even aware of this finding.
We have to travel to Europe in order to find data that clearly shows that a synthetic progestin does not have the same health risk profile as other forms of progesterone.
Fournier and his group in France published in 2007 their findings in a journal called Breast Cancer Research. They studied over 80,000 postmenopausal women over 8 years, and they compared different hormone regimens.
Compared to women who never used any hormone therapy, women who used only estrogen had a 29% increase in their risk of breast cancer. If they used estrogen plus a synthetic progestin, the risk went up 69%.
However, in women who used a bioidentical form of progesterone, there was NO increased risk compared to women who never used any hormone therapy.
(A subset of these women also used a bioidentical form of estrogen, which showed a further protective effect against breast cancer. In other words, this group of women had a LOWER chance of breast cancer than women who never used any hormone therapy!)
So what is Helen going to do?
For now, she is off of all of her hormones. I hope she will feel OK for as long as possible, get through her treatment, and we will use non-hormonal methods of handling any menopausal symptoms as they may occur.
It’s going to be a long time until the science of risk of different hormone treatments outpaces the scary media coverage.
In the meantime, I will do my best to arm women with the information they need to not be afraid to use the right hormone treatments to feel their best.