The facts are as follows: there was, happily, a 7% drop in breast cancer in 2003. The drop was sustained in 2004.

While this is great news, let's be clear about what is fact and what is not.

1. No one knows why the rates dropped. The idea that a decreased use of hormones is responsible is simply conjecture.
2. It has never been shown that estrogen actually causes breast cancer. It will cause an estrogen positive tumor to grow, but that is very different.
3. The double-blinded, placebo controlled Womens Health Initiative estrogen-only study of 10,000 women showed a 23% decrease in breast cancers in the estrogen-only users versus placebo users. Placebos are "dummy pills" that have only sugar in them, no drugs.
4. Breast cancer mortality after estrogen use has been generally 50% lower in numerous studies. This may be because estrogen promotes the growth and detection of cancers before they have a chance to spread and cause death.
5. It may be that the decline in breast cancer diagnosis may represent a decrease in detection only. It takes about 8 years for a breast cancer tumor to develop to a size that can be detected.
6. After the huge media frenzy following the announcement that Premarin and Provera caused an unacceptable increase in risk of breast cancer, many women stopped using Premarin and Provera. Since it appears that Provera, or synthetic progesterone, is a culprit in causation of breast cancer, it may be that the decreased use of Provera is responsible for the decrease in breast cancers.
7. It may be that the sudden drop-off in Premarin (horse urine derived estrogen) in favor of bioidentical estrogen may be partially responsible.
8. It may be that the specific interaction of these 2 hormones (Premarin and Provera) is causing breast cancer.

The bottom line is that we cannot jump to the conclusion that ALL estrogen, including bioidentical, causes breast cancer. In fact, there is ample evidence that bioidentical estrogen is beneficial to the body and helps the body fight disease.

As far as progesterone goes, we do not yet know whether the proven progesterone associated increased risk of breast cancer is specific to the synthetic progesterone medroxyprogesterone acetate (Provera) or can be generalized to all progesterones, including bioidenticals.

Intuitively, we figure that the bioidenticals are safer, and I must say that I agree with that notion. After all, bioidentical hormones are the same molecules that our bodies make before we are menopausal. However, there are no studies to support this assumption yet.

In conclusion, I would encourage women who are taking bioidentical estrogens (pellets, patches, creams, or pills) without progesterone, to relax. These would be the women without a uterus who take estrogen alone.

If you are taking progesterone because you have a uterus, here are some thoughts:

1. The well designed Womens Health Initiative hormone trials show that breast cancer risk increases among women aged 50-79 years after 5 years of exposure to estrogen and progesterone (Provera) to an additional 0.8 cases per 1,000 women per year. Risk is not associated, as mentioned above, with use of estrogen alone.
2. In the case of distressing menopausal symptoms, short-term therapy with estrogen and progesterone will have little effect on personal risk of breast cancer.
3. Longer use of estrogen and synthetic progesterone therapy increases the breast cancer risk. However, the level of risk remains similar to many risks women accept through lifestyles that expose them to daily alcohol ingestion, lack of regular exercise, and postmenopausal obesity.
4. Gynecologists have always been taught that a woman with a uterus may not take estrogen alone due to a risk of overstimulation of the uterine lining leading to uterine cancer. Progesterones are given along with estrogens to mitigate this effect on the uterine lining and prevent uterine cancer. It appears, however, that the number of endometrial (uterine) cancers prevented by the addition of progesterone may be smaller than the number of breast cancers attributed to its use. One study estimated that for every 10 endometrial cancers prevented over 10 years, 14 breast cancers were caused by the addition of progesterone to estrogen treatment.

A woman who has a uterus and wants to take estrogen alone to avoid the risks associated with progesterone use would need to discuss this idea in detail with her practitioner. Ultrasounds and endometrial biopsies would be necessary every 6 months to monitor the uterine lining. If she did any bleeding, she would need to report it immediately.

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