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LETTER: Task force recommendations on breast cancer screening are flawed

A radiologist uses a magnifying glass to check mammograms for breast cancer in Los Angeles. The latest report from a long-term Canadian study suggests that breast cancer screening isn't reducing the number of breast cancer deaths. Damian Dovarganes / CP
A radiologist uses a magnifying glass to check mammograms for breast cancer.

If a Canadian wide-body jet crashed due to maintenance problems, killing all 400 people onboard, it would viewed as a national disaster and would occupy the news for weeks. If this happened each year it would be seen as an epidemic.

But 400 is approximately the number of avoidable breast cancer deaths expected to occur in Canadian women each year if the recent recommendations on breast cancer screening by The Canadian Task Force on Preventive Health Care (CTF) are adopted.

The CTF is composed of methodological experts with no specific knowledge of breast cancer screening or treatment, ostensibly to avoid bias. It operates at arm’s length from government, i.e., its operations are unsupervised. One would expect that the mission of the CTF would be to recommend how to prevent deaths and suffering from breast cancer. Instead it seems that its goal is simply to reduce access to screening.

A wealth of information demonstrating the benefits of earlier cancer detection through screening is available, but the CTF has chosen to restrict its view only to randomized controlled trials (RCTs). RCTs are the gold standard for cancer trials and this would be a good idea if such trials testing current breast cancer practices existed, but they don’t.

Such trials won’t ever be done now because: 1) they are extremely costly; 2) the answers don’t come for 15 years or more; 3) technology will change during that time; and 4) most importantly, because scientists who consider all the data are already convinced that screening women from age 40 to 70+ years reduces breast cancer deaths.

That evidence comes from the scientific publications from both the RCTs done 25-50 years ago and from monitoring outcomes from mammography screening programs around the world that use up-to-date approaches for screening and treatment.

The CTF has also ignored the findings that screen-detected breast cancers require less harsh therapies like mastectomy, armpit node surgery (resulting in swelling of the arms) and toxic chemotherapy.

While demanding RCT data as evidence of benefit, the CTF used a lower threshold for publications for evidence of harm, and didn’t put that harm into perspective. Also, it didn’t examine the original data itself, but used a third party group who also lacked expertise in breast cancer screening to review and summarize the severely restricted evidence. And, because the CTF ignored attempts of several experts to provide them with factual data, it even got some of the numbers wrong and grossly overstated the harms associated with screening (false positives, extra needle biopsies and overtreatment of “sleepy” nonkiller cancers).

The CTF will spend a lot of our tax money on communication tools to try to convince doctors and the public that less screening is a good idea.  It will suggest that few cancers occur each year and few lives in those women will be saved each year. These numbers will look very small. But scale them up to the Canadian population and the story looks very different – about 400 lives per year saved. And for the women in their 40s, each death prevented represents about 20 extra years for a woman to live her life.

One of the biggest harms of current screening is that mammography is less accurate for women with dense breasts, something glossed over by the CTF.

If women are informed that they have dense breasts, they can be referred to another screening method such as ultrasound that will be more reliable for them — a move toward personalized medicine explicitly rejected by the CTF.

These CTF recommendations suggest “shared decision making” by a woman and her healthcare provider. I agree fully, but this requires accurate information, something that the CTF has not provided. The recommendations are misleading, dangerous and a waste of tax dollars.

Like a poorly-maintained airplane, they should be grounded. Because if the recommendations are adopted, every Canadian woman could be on that plane.

Martin Yaffe

Tory Family Chair in Cancer Research,

Sunnybrook Research Institute, Toronto

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