New study questions link between HRT and breast cancer

Robin Wulffson MD's picture
breast cancer, hormone replacement therapy, HRT, estrogen, progestogen, Premarin
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CAPE TOWN, SOUTH AFRICA - Whether to take hormone replacement therapy (HRT) for menopausal symptoms continues to be controversial. Many women choose not to take HRT for fear of an increased breast cancer risk. According to a new study, the link between breast cancer and HRT is based on "unreliable evidence."

The study was published online on January 16 in the Journal of Family Planning & Reproductive Health Care by researchers at the University of Cape Town Medical School in South Africa.

According to the researchers, the claim that HRT with estrogen plus progestogen is an established cause of breast cancer is based principally on the findings of three studies: the collaborative reanalysis, the Women's Health Initiative, and the Million Women Study (MWS). The results of these studies, which were reported in the early 2000s, led to warnings about the risk for breast cancer from HRT, and resulted in a marked decrease in the use of these products. The study authors, however, claim that that those studies do not prove causality. They reviewed data from all three studies and the current study focused on the MWS. They wrote: "HRT may or may not increase the risk of breast cancer."

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The research team, led by Samuel Shapiro, MB, visiting professor of epidemiology at the university, noted that the MWS study suggested a greater risk for breast cancer with HRT than either the collaborative reanalysis or the Women's Health Initiative, and it had a huge impact on regulatory authorities and on the public perception of safety. They added that it was the largest study of HRT and breast cancer ever conducted, and its name, the Million Women Study, implies an authority beyond criticism or refutation.” In addition they claimed that size alone does not guarantee that the findings are reliable. They concluded that after examining the validity of the study in some detail, the evidence from the MWS is "unreliable." They explained that there were defects in the study design, and find evidence of detection bias and confounding, issues with internal and external consistency, as well as other problems.

The principal investigator of the MWS, Dame Valerie Beral, AC, DBE, FRS, MRCP, professor and head of the Cancer Epidemiology Unit at Oxford University, UK, refuted the authors’ findings. She noted, "These issues are not new and have been refuted previously." She claims that the South African Study is as a "restatement of views held by many consultants to HRT manufacturers [as these authors are] attempting to dispute evidence about the adverse effects of HRT." She noted that the authors neglected to mention that "the MWS findings of an increased risk of breast cancer in users of HRT, especially of estrogen–progestogen combinations, have now been replicated in over 20 other studies… The totality of the worldwide evidence is now overwhelming" She added, "In line with the findings from these studies, the recent large decrease in HRT use has been followed in many countries by a nationwide decline in the incidence of breast cancer.”

Editorial Comment:
Recent studies have reported less breast cancer risk with low-dose estrogen patches (no progestogen). These patches release a small dose of estrogen into the blood stream, just as a functioning ovary does. Many of the past HRT studies are based on a popular oral form of estrogen: Premarin. Oral estrogen is digested and passes through the liver before entering the blood stream. The liver, sensing a high estrogen level, removes it from the circulation and metabolizes it. Premarin is derived from pregnant mares’ urine. (PREgnant MARes’ urINe). Horse estrogen is similar to, but not identical with human estrogen. In addition to preventing hot flashes, estrogen reduces the risk of osteoporosis; in addition, it keeps the skin and vaginal tissues healthier. Some studies have suggested that estrogen reduces the risk of Alzheimer’s disease. For many women who develop breast cancer after the menopause, the disease does not impact their longevity. A hip fracture due to osteoporosis can be a major life-changing event. A hip fracture can lead to death, either from complications of the surgery or later events. Women whose lifestyle is impacted by a hip fracture (i.e., wheelchair-bound) become severely depressed.

Reference: Journal of Family Planning & Reproductive Health Care

See Also:
Prevent breast cancer: drink red wine
Should you tell your children they have increased cancer risk?
Women's sexual satisfaction increases with age, new study reports

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Comments

How many women with breast cancer took birth control pills or fertility treatments? It seems to be the single common denominator among survivors whom I speak to. Most developed their cancer while pre menopausal and took the pill for 3-20 years.