I have received so many emails and telephone calls from patients expressing concern over taking hormone replacement therapy. This was after a new report was published in JAMA, “ Estrogen Plus Provera and Breast Cancer Incidence and Mortality in Postmenopausal Women”.
The study drew much attention from just about every TV news broadcast station as well as major national newspapers. The report was a further analysis of the Women’s Health Initiative ( WIH) randomized study of postmenopausal women taking Premarin plus Provera, Premarin alone or placebo.
They found that after 11 years of followup, women taking Premarin and Provera had an increased risk compared to those taking placebo of invasive breast cancer (0.42% vs 0.34% per year) and death attributable to breast cancer (0.026% vs 0.013%). This is actually about one more invasive breast cancer per 1,000 women per year and a little over one more death per 10,000 women per year.
This adds fuel to the fire—that women should only consider HRT for severe, unbearable symptoms only for the shortest period of time or better yet don’t take HRT at all. Again, all HRT is lumped into the same category ignoring the fact that not all hormones are equal.
Premarin is actually derived from pregnant mare urine and is not molecularly identical to the estrogen that naturally occurs in a woman’s body. Also, premarin was administered orally. Even though not ideal, an arm of the WHI involved women who had a previous hysterectomy and were given Premain. In these participants, an increase in breast cancer was not observed but rather a 23% decrease compared to the placebo group.
On the other hand, Provera is not progesterone (even though many times the names have been used interchangeably). Provera is actually medroxyprogesterone acetate (MPA), a synthetically altered form of the molecule that naturally occurs in a woman’s body called progesterone. One could conclude that Provera may be the bad player since the group that took Premarin and Provera had the increase risk in breast cancer not the Premarin only group.
There is evidence to support the statement that not all progestins are alike in their effect on breast cancer risk. A large European study (E3N) that followed 80,377 women on various progestin/estrogen combinations (none on MPA) for 10 years showed no increase risk of breast cancer. There is also a study that showed progesterone had an inhibitory effect on the proliferation of breast cancer cells whereas Provera did not.
So what is the bottom line? Not all progestins are the same. The results from a study with one progestin should not be generalized to all progestins.
I believe that not all HRT is the same. As a woman taking bio-identical hormones, I feel confident that the overall benefits outweigh the risks for myself. Obviously, this is a personal decision for all of us but there is evidence of its safety and more studies are currently in progress.