Breast Cancer Linked To HRT Use

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Main Category: Breast Cancer
Also Included In: Menopause;  Pharma Industry / Biotech Industry
Article Date: 19 Apr 2007 - 0:00 PST

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A new study suggests the decrease in breast cancer in the US in 2003 is linked to reduced use of hormone replacement therapy (HRT).

The study is published in the New England Journal of Medicine (NEJM).

According to researchers using data from the US National Cancer Institute (NCI) Surveillance, Epidemiology and End Results (SEER) programme, there was a sharp fall of 6.7 per cent in the age-adjusted rate of new breast cancer cases in the US in 2003.

They suggest this could be linked to the decline in the use of HRT during the same period.

HRT prescriptions fell sharply after the Women's Health Initiative (WHI) study suggested that postmenopausal women on HRT using both estrogen and progestin carried an increased risk of breast cancer, heart disease, stroke, blood clots, and urinary incontinence.

The two HRT drugs most commonly prescribed in the US are PREMARIN (estrogen-only) or PREMPRO (a combination of estrogen and progestin), both made by Wyeth Pharmaceuticals. Prescriptions for these two drugs fell from 61 million in 2001 to 21 million in 2004.

The study shows that new cases of breast cancer starting falling in mid-2002 and levelled off after 2003. The decrease occurred only in women over 50 and was sharper for estrogen receptor (ER) positive cancers. In ER positive cancer, estrogen stimulates growth and spread of tumour cells.

The research team, led by Dr Donald Berry from the University of Texas MD Anderson Cancer Center in Houston, Texas, suggest that the speed with which breast cancer rates fell may be because extremely small ER-positive breast cancers stopped progressing, or even regressed, after HRT was stopped following the WHI announcement.

NCI Director, Dr John E. Niederhuber, said:

"Breast cancer is the most frequently diagnosed cancer among women in the United States, and we have made great strides in its treatment."

"Still, we don't know all the causes of breast cancer, and breast cancer rates had been increasing for two decades up to 2002. Finding the simple ways, such as limiting HRT use to decrease breast cancer risk, is a step forward," he added.

Exactly how stopping HRT affects breast cancer is not well understood. It depends on which treatment is followed and how the patient responds to the drugs.

The NCI suggest that the nationwide reduction in breast cancer due to reduced use of HRT may have run its course and incidence may even rise again. Also, there is no evidence to suggest that reduction in HRT has long term effects or whether it simply slowed down the detection of tumours -- so we may see incidence rise again.

The scientists explored other reasons that might explain the sharp decline in new breast cancer cases, including changes in reproductive factors, mammography screening rates, environmental exposure, and diet.

Dr Kathy Cronin of the NCI Surveillance Research Program, said:

"Recent reports have suggested a small decline in mammography use after 2000. Screening may play a role as well, and the contribution of mammography to the observed decline in incidence is currently being investigated."

More research is needed, along the lines of randomized clinical trials, to prove a link between HRT use and new breast cancer cases. This study is based on population statistics and therefore cannot be used to establish cause, only association.

The WHI trial is a randomized controlled trial. A report due later this year is expected to give detailed evidence of the effect of continuing and ceasing HRT on breast cancer incidence.

A statement released yesterday from Wyeth Pharmaceuticals asks that people treat the findings of this study with a degree of caution, drawing attention to the fact it is not a randomized trial and therefore cannot establish a causal link between HRT and breast cancer incidence.

They too point out that the long term effects are unknown, and suggest that other factors, such as the reduction in mammography exams may just have reduced the ability to detect breast cancer early, rather than actually reduced the incident rate. We may well see a rise in detection of later stage breast cancer if that is the case.

Dr Joseph Camardo, Senior Vice President of Global Medical Affairs for Wyeth Pharmaceuticals said that:

"Reports such as this cause confusion, the hypothesis put forth in this report does not change what we know about hormone therapy, which is based on data from numerous, more rigorous studies including the Women's Health Initiative."

"Hormone therapy remains a good health care choice for the appropriate woman seeking the relief of moderate to severe menopausal symptoms, including hot flashes, night sweats and vaginal atrophy, and the prevention of postmenopausal osteoporosis," he added.

Wyeth recommend that HRT be used at the "lowest dose for the appropriate duration consistent with treatment goals and risks for the individual woman," and encourages women to speak to the their doctor about what is the right treatment and to continue with routine mammogram screening.

Dr Christine Berg of the NCI and co-researcher on the study said:

"The decision about use of HRT is complex. While HRT provides relief from the symptoms of menopause, it may also increase one's risk of breast cancer. It is important that women meet with their doctor to discuss what decision is right for them, particularly if they are at high risk for breast cancer."

Meanwhile, another study being published today in the Lancet, attributes 1,000 extra ovarian cancer deaths in the UK since 1991 to HRT.

"The Decrease in Breast-Cancer Incidence in 2003 in the United States."
Ravdin, Peter M., Cronin, Kathleen A., Howlader, Nadia, Berg, Christine D., Chlebowski, Rowan T., Feuer, Eric J., Edwards, Brenda K., Berry, Donald A.
N Engl J Med 2007 356: 1670-1674.
April 19, 2007; Number 16

Click here for Abstract.

Click here for National Cancer Institute (US)

Click here for article: 1,000 Ovarian Cancer Deaths In The UK Caused By HRT, Says New Study.

Written by: Catharine Paddock
Writer: Medical News Today


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