Hormone therapy breast cancer risk study

[Guest guest]

I just realized that some people don't like to open URLS so here is the article

about the new study.

Marie

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The Canadian Press

Updated: Fri. Sep. 24 2010 8:31 AM ET

TORONTO — The first Canadian study of its kind is adding to a growing body of

international evidence suggesting that the use of hormone replacement therapy

may raise the risk of breast cancer.

However, some doctors counter that such studies do not prove a cause-and-effect

association between taking hormones and the onset of breast cancer, and stress

there could be many other factors playing a role in the development of the

disease.

The study by the Canadian Cancer Society found there was a significant decrease

in the rate of new breast cancers among post-menopausal women between 2002 and

2004 -- coinciding with a huge drop in the use of hormone replacement therapy,

or HRT.

Many Canadian women stopped taking hormones in 2002 after a massive U.S.

clinical trial -- the Women's Health Initiative -- suggested the risks of taking

HRT outweighed the benefits. That study suggested taking hormones appeared to

increase the risk of breast cancer, heart attack, stroke and blood clots in the

lungs.

Following release of that data, the proportion of Canadian women taking HRT

began falling dramatically. In 2004, just five per cent of women aged 50 to 69

were on the drugs, compared to 13 per cent in 2002.

" The drop in breast cancer incidence was fairly significant, " said lead author

Prithwish De, an epidemiologist with the Canadian Cancer Society. " We saw a 10

per cent drop in the incidence rate of breast cancer from 296 per 100,000 women

to about 278 per 100,000. "

At the same time, the rate of mammography did not change and so was not a

factor, say the authors, whose report was published online Thursday in the

Journal of the National Cancer Institute.

De said the study is the first national analysis of HRT use and breast cancer

incidence rates in Canada. It follows a similar U.S. study published in 2007,

which found disease rates plunged in 2003, the year after millions of American

women stopped taking hormone pills.

" It certainly gives a Canadian perspective to the growing international evidence

around the association between breast cancer incidence and HRT, " he said. " It

also supports the Canadian Cancer Society position (that) women should avoid

using HRT for any reason other than managing severe menopausal symptoms. "

Yet, the study also turned up an interesting finding that has led some to

question the validity of the HRT-breast cancer link.

The decline in breast cancer incidence continued until 2005, dropping to 266 per

100,000 women, after which the annual rate began to rebound -- rising to about

279 per 100,000 in 2006 -- even though hormone therapy use was virtually

unchanged from 2002.

Dr. Blake, chief of obstetrics and gynecology at Sunnybrook Health

Sciences Centre in Toronto, said after examining the study data that " it's very

hard for me to be convinced. "

" There's just so many unknowns, " said Blake, who was not involved in the study.

" I think we have to be very clear when we look at these studies that we're not

able to make any kind of a causative relationship. All you're saying is that

there's an observation of an association and you don't have any way of knowing

whether they're related. "

She said there are many risk factors for breast cancer -- including obesity and

the age at which a woman has her first period, first child and goes into

menopause. As well, the risk of developing the disease increases with age.

The short window between the drops in hormone use and breast cancer incidence

also raises a red flag, said Blake, since many studies have shown that it takes

about five years from discontinuing hormone therapy for breast cancer risk to

return to " baseline. "

Dr. Derzko, an obstetrician and gynecologist at St. 's Hospital

in Toronto, said the rebound in incidence in 2006 cannot be ignored.

" We have to ask the question why was that. We have to ask was the drop before

that real, " said Derzko, pointing out that it takes about seven to 10 years for

a breast tumour to develop to detectable levels from the rise of the first

cancerous cell.

" If you stop a hormone, why should all this disappear? "

The theory is that taking hormones can make small but undetectable breast

cancers grow, and when hormone therapy is stopped, then growth stops, she said.

" It's less obvious, so the pickup rate (by mammogram or physical examination)

may be less. "

" Subsequently ... a few years later, eventually just on their own steam, they

have grown to the point where they are seen, " she said.

While hormone is not the only answer to dealing with menopause, Derzko said

menopausal women should discuss with their physicians what is appropriate for

treating hot flashes and other unpleasant and disruptive symptoms.

" We are not uncomfortable with providing hormones to women who are between 50

and 60 ... immediately in the post-menopausal period, " she said. " Their

consideration of hormone therapy should remain on the list. "

" But it's incumbent on them and us as physicians to make sure we are watching

them, that we're making sure their mammograms are done. "