A significant drop in breast cancer among post-menopausal Canadian women from 2002 to 2004 coincided with a sharp drop in hormone replacement therapy (HRT) use during the same period, a new study shows.
The study, released by the Canadian Cancer Society and published in the Journal of the National Cancer Institute, is the first to show a link between HRT use and breast cancer incidence among Canadian women.
In 2002, the Women’s Health Initiative (WHI) trial of more than 16,000 postmenopausal women in the United States reported that the risks of combined estrogen and progesterone hormone replacement therapy outweighed the benefits.
As a result, prescriptions for hormone therapy fell dramatically not only in Canada but in several countries around the world—as did the incidence of breast cancer.
The Canadian researchers say the drop in HRT use may be partly explained by the media’s coverage of the WHI and the Million Women Study in the United Kingdom, both of which showed that breast cancer risk was elevated with the use of combined hormone therapy.
The Canadian study shows that from 2002 to 2004 the breast cancer incidence rate dropped by nearly 10 percent among Canadian women aged 50 to 69—the largest age group of HRT users in Canada.
This coincided with a more than 50 percent drop in the number of women in the same age group taking HRT between 2002 and 2004, with HRT use dropping from almost 13 per cent to five percent.
During the same period, the rate of mammography use stayed the same, suggesting 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,” said Dr. Prithwish De, the study’s lead investigator and an epidemiologist at the Canadian Cancer Society.
The society suggests women avoid taking HRT for any reason other than to relieve severe menopausal symptoms that have not responded to other treatment.
Heather Chappell, director of Cancer Control Policy with the Canadian Cancer Society 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,” she says. “If a woman decides to take HRT, she should take the lowest effective dose for the shortest time possible.”
While the risk of breast cancer increases the longer a woman takes HRT, that risk drops rapidly after the hormone therapy is stopped. Mammography is less effective in women who use HRT because of increased breast density, according to the society.
Additional findings show that there was little change in breast cancer rates in women under 50 and among older women aged 70 and over, and that the decline in breast cancer rates among women aged 50 to 69 continued until 2005, after which time rates began to increase slightly.
“This study fills a gap in our knowledge about the link between HRT use and breast cancer risk for Canadian women,” said De. “We anticipate that more research in this area will continue to shed light on this crucial health issue for Canadian women.”
Worldwide, breast cancer remains the most common type of non-skin cancer among women, according to the International Agency for Research on Cancer. In Canada, 80 percent of breast cancer cases occur among women aged 50 and older, and 52 per cent among those aged 50 to 69.
The study, released by the Canadian Cancer Society and published in the Journal of the National Cancer Institute, is the first to show a link between HRT use and breast cancer incidence among Canadian women.
In 2002, the Women’s Health Initiative (WHI) trial of more than 16,000 postmenopausal women in the United States reported that the risks of combined estrogen and progesterone hormone replacement therapy outweighed the benefits.
As a result, prescriptions for hormone therapy fell dramatically not only in Canada but in several countries around the world—as did the incidence of breast cancer.
The Canadian researchers say the drop in HRT use may be partly explained by the media’s coverage of the WHI and the Million Women Study in the United Kingdom, both of which showed that breast cancer risk was elevated with the use of combined hormone therapy.
The Canadian study shows that from 2002 to 2004 the breast cancer incidence rate dropped by nearly 10 percent among Canadian women aged 50 to 69—the largest age group of HRT users in Canada.
This coincided with a more than 50 percent drop in the number of women in the same age group taking HRT between 2002 and 2004, with HRT use dropping from almost 13 per cent to five percent.
During the same period, the rate of mammography use stayed the same, suggesting 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,” said Dr. Prithwish De, the study’s lead investigator and an epidemiologist at the Canadian Cancer Society.
The society suggests women avoid taking HRT for any reason other than to relieve severe menopausal symptoms that have not responded to other treatment.
Heather Chappell, director of Cancer Control Policy with the Canadian Cancer Society 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,” she says. “If a woman decides to take HRT, she should take the lowest effective dose for the shortest time possible.”
While the risk of breast cancer increases the longer a woman takes HRT, that risk drops rapidly after the hormone therapy is stopped. Mammography is less effective in women who use HRT because of increased breast density, according to the society.
Additional findings show that there was little change in breast cancer rates in women under 50 and among older women aged 70 and over, and that the decline in breast cancer rates among women aged 50 to 69 continued until 2005, after which time rates began to increase slightly.
“This study fills a gap in our knowledge about the link between HRT use and breast cancer risk for Canadian women,” said De. “We anticipate that more research in this area will continue to shed light on this crucial health issue for Canadian women.”
Worldwide, breast cancer remains the most common type of non-skin cancer among women, according to the International Agency for Research on Cancer. In Canada, 80 percent of breast cancer cases occur among women aged 50 and older, and 52 per cent among those aged 50 to 69.
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