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  • J. Charles Lamb

The U.S. may lower the breast cancer screening age to 40. Should Canada follow?

A U.S. health task force is recommending women get screened for breast cancer 10 years earlier than the current mammogram recommendation, and experts in Canada believe the country should follow suit in order to save more lives.

The U.S. Preventive Service Task Force on Tuesday proposed that all women get screened every other year starting at age 40. That would be a change from current U.S. guidelines, advising screening to start at age 50.

The health panel said the move would save thousands of lives per year.

“We have been advocating for this in Canada for over 10 years,” said Dr. Jean Seely, head of breast imaging at the Ottawa Hospital. “The importance of women getting breast cancer screening in their 40s cannot be overstated.”

The number of women who are getting breast cancer in their 40s is increasing, which is one of the reasons the U.S. task force changes its guidelines, she said.

“New and more inclusive science about breast cancer in people younger than 50 has enabled us to expand our prior recommendation and encourage all women to get screened in their 40s,” the task force stated on its website.

In Canada, regular screening mammography is only recommended for patients between the ages of 50 and 74; but women in their 40s could be able to have a screening if they talk to their doctors.

The requirement of a doctor’s referral for women aged 40-49 to undergo a mammogram could pose a challenge to receiving assistance, Seely said. She explained that a physician may be reluctant to provide the referral, or an individual may not have access to a family doctor.

“What we’re advocating for is to have all women who are 40 or older be able to self-refer to a screening program to remove that barrier,” she said.

Screening protocols differ throughout Canada. Breast cancer screening for individuals aged 40 and above is conducted annually in Nova Scotia, P.E.I, and Yukon. Similarly, in British Columbia, screening starts at age 40, but not on an annual basis. Alberta’s routine screening program starts at age 45.

However, provinces such as Manitoba, Ontario and Quebec, still start routine screening at age 50.

A 2022 Canadian study found between 2010 and 2017, Canadian women aged 40–49 were diagnosed with more stage two and three breast cancers than women 50–59 years old.

In the same period, women 40–49 years old in provinces that screened that age bracket, were diagnosed with significantly fewer stages two, three and four breast cancers than those living in the comparator provinces.

Why doesn't Canada recommend screening at age 40?

The Canadian Task Force on Preventive Health Care, which issues national guidance, conditionally recommends against mammography screening for women aged 40 to 49 who are not at increased risk.

“If women in this age group wish to be screened, they should have a discussion with their health-care provider to decide if screening is best for them,” read the guidelines that were last updated in 2018.

However, the guidelines webpage indicates that the “tools are currently under review and will be updated in early 2023.”

Jennie Dale, co-founder and executive director of Dense Breast Cancer, has been petitioning the federal government to lower its routine mammogram testing recommendation to 40.

Women aged 40–49 are more likely to have dense breasts, which can increase the risk of breast cancer, she said. And mammography in women with extremely dense breasts may be more effective if it is performed yearly.

Because of these reasons, she said the study the government based its decision on is “outdated and flawed.”The two Canadian trials Dale cited found that screening for breast cancer for women in their 40s did not reduce death rates from breast cancer.

However, many experts, including Dale and Seely, said the studies have flawed methodology and biases.Other studies, Dale said, have found the opposite, that mammograms for women in their 40s do reduce mortality rates.

For example, a 2014 study published in the Journal of the National Cancer Institute, including 2.8 million Canadian women, found that those who have mammograms starting at age 40 were 40 per cent less likely to die of breast cancer than women who don’t have mammograms.

According to the Canadian Task on Preventative Health Care, screening in women aged 40–49 reduces the relative risk of dying of breast cancer by 15 per cent.

Another reason, Canada does not recommend routine mammograms for women in their 40s, is due to concerns about overdiagnosis; when patients are screened at a younger age it can lead to unnecessary treatment of cancer that may have not caused an illness.

Seely disagrees with this concern.

“The harms of overdiagnosis are actually almost zero in women in their forties,” she argued. “If you get breast cancer and you’re in your forties, that is most likely going to actually lead to death rather than a woman in her seventies or eighties, because an older woman has other competing causes of death.”

Cost to the health-care system may be a reason Canada’s guidelines haven’t changed, Seely said. But she argued that preventative measures, like early screening, could actually save the health-care system millions of dollars.

“Screening is actually a low cost to the system,” she said. “And treatment costs have increased, in particular in women who have more advanced stage breast cancer,” she said, adding this is because of new costly therapies.

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