Friday, September 24, 2010

Drop in Breast Cancer Incidence among Canadian Women Linked to Decline in Hormone Replacement Therapy (HRT) Use

Landmark Findings Released by Canadian Cancer Society

TORONTO, September 23, 2010 /Canada NewsWire/ - A new Canadian study shows that a significant drop in breast cancer incidence among post-menopausal women from 2002 to 2004 coincided with a sharp drop in hormone replacement therapy (HRT) use during the same period. This is the first study to show the link between HRT use and breast cancer among Canadian women.

Many Canadian women stopped taking HRT in 2002 because the results from a large American clinical trial - the Women's Health Initiative - showed the risks of taking HRT outweighed the benefits.

These new findings add an important Canadian perspective to growing international evidence that HRT use is linked to increased breast cancer risk. The study is published online today in the Journal of the National Cancer Institute.

The Canadian Cancer Society research shows that from 2002 to 2004 the breast cancer incidence rate dropped by nearly 10 per cent among Canadian women aged 50-69. This coincided with a more than 50 per cent drop in the number of women in the same age group taking HRT between 2002 and 2004 (HRT use dropped from almost 13 per cent to five per cent).

This is the largest age group of HRT users in Canada.

During the same period, the rate of mammography use stayed the same for Canadian women. This suggests that the drop in breast cancer incidence was not due to fewer women getting mammograms. The only factor that changed substantially was HRT use.

"These findings give Canadian women meaningful information about breast cancer and how to reduce their risk of getting this disease," says Dr. Prithwish De, the study's lead investigator and an epidemiologist at the Canadian Cancer Society. "Breast cancer is the most common cancer among Canadian women, and we hope these findings will help lead the way to seeing fewer women diagnosed with this disease."

Currently, the Society recommends that women avoid taking HRT for any reason other than to relieve severe menopausal symptoms that have not responded to other treatment.

"These findings reaffirm the Society's position on the risks of HRT use and reinforce the importance of getting this message to Canadian women," says Heather Chappell, Director, Cancer Control Policy, Canadian Cancer Society. "As we approach Breast Cancer Awareness Month, this is one more piece of information we can give Canadian women to help them fight back against this disease."

Chappell urges women approaching menopause to talk to their doctors about the risks and benefits of taking HRT to determine the best course of action for them. "The severity of each woman's menopausal symptoms and her medical history should be considered. If a woman decides to take HRT, she should take the lowest effective dose for the shortest time possible."

The Canadian Cancer Society study

The research team estimated HRT use among Canadian women between 1996 and 2006 by examining data from the National Population Health Survey. This information was examined alongside national breast cancer incidence rates for the same time frame obtained from the Canadian Cancer Registry. The study focused primarily on combined HRT (estrogen plus progestin).

Additional findings from the research show:

...There was little change in breast cancer incidence rates in younger women (under age 50) and among older women (over the age of 70).

...The decline in the breast cancer incidence rate among women aged 50-69 years continued until 2005, after which time rates began to increase slightly.

...In 2002, nearly 30 per cent of Canadian women aged 50-69 were taking some form of hormone therapy. This dropped to 15 per cent in 2004.

"This study fills a gap in our knowledge about the link between HRT use and breast cancer risk for Canadian women," says De. "We anticipate that more research in this area will continue to shed light on this crucial health issue for Canadian women."

In addition to De, the members of the research team are:

Dr C. Ineke Neutel, Department of Epidemiology and Community Medicine, University of Ottawa

Dr Ivo Olivotto, Breast Cancer Outcomes Unit, BC Cancer Agency

Dr Howard Morrison, Centre for Chronic Disease Prevention and Control, Public Health Agency of Canada.

October is Breast Cancer Awareness Month. The Canadian Cancer Society fights back against breast cancer by:

...supporting excellent breast cancer research
...educating women about early detection
...providing information and support to women living with breast cancer, their families and their caregivers

The Canadian Cancer Society fights cancer by doing everything we can to prevent cancer, save lives and support people living with cancer. Join the fight! Go to to find out how you can help. When you want to know more about cancer, visit our website at or call our toll-free bilingual Cancer Information Service at 1 888 939-3333.

For a copy of the research paper entitled Breast Cancer Incidence and Hormone Replacement Therapy in Canada please go to:

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