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Alan Cassels: Too many misled on breast-cancer screening

I was about to call it a day when an email arrived with the following in the subject line: “The Best Health Advice You’ll Get Today.” That caught my attention. I was curious. And I’m a sucker for free health advice.

I was about to call it a day when an email arrived with the following in the subject line: “The Best Health Advice You’ll Get Today.” That caught my attention.

I was curious. And I’m a sucker for free health advice. I’ve got more than just a passing interest in health advice, seeing as I spend many of my working hours examining the quality of evidence that underlies what people say about drugs, screening and other kinds of health treatments. So when someone wants to offer me the “best,” I sit up and pay attention.

I quickly learned this email was sent to me from the Canadian Breast Cancer Foundation as part of their monthly update. The email was essentially reminding me about how important breast-cancer screening is and how often women should subject themselves to it.

“Mammograms save lives,” read the headline. My heart sank. Not only is this headline unlikely to be true, it’s possibly dangerous. The headline followed with the statistic that “regular mammograms for women age 40 and over equal a 25 per cent reduction in the number of breast cancer-related deaths.”

Many scientists who have looked closely at the evidence have soundly questioned routine mammograms for healthy women (those with no extra risk factors for the disease), and particularly for younger women (those between ages 40 and 59) because of the very real problems of overdiagnosis and overtreatment.

So why is an organization dedicated to this serious condition sending out such misinformation — and why now, I wondered? Because, as the email says: “There appears to be much information of late in popular media about who should go [for screening] and how often.”

In other words, perhaps they felt it was time to counter what the scientists were saying. It was three years ago in the Canadian Medical Association Journal when Danish screening expert Dr. Peter Gotzsche asked a provocative question: Which country was going to be the first one to stop mammography? He was also the lead author of a review of mammography that included seven trials involving 600,000 women between 39 and 74 years, randomly assigned to receive screening mammograms or not and found that the screening did not reduce breast-cancer deaths.

Then in February, a 25-year study by Cornelia Baines and Anthony Miller at the Dalla Lana School of Public Health in Toronto added weight to that assessment, finding that annual breast-cancer screening of women age 40 and 59 does not reduce breast-cancer death rates compared to regular physical examination or usual care.

This message got a fair bit of media play because it was, after all, a Canadian study and one of the biggest and highest-quality studies ever done on breast-cancer screening.

This research is adding up to what I would call a wholesale re-questioning of the need for mammography, based on the fact that the overall benefits seem to be vanishingly small and the harms — including unnecessary cancer scares, biopsies and surgeries — considerable.

A recent article in the New England Journal of Medicine suggests that Switzerland might be the first nation in the world to dismantle its breast-cancer screening program for women of average risk. In a report prepared by the Swiss Medical Board, the authors wrote that mammography screening of women between 50 and 69 might prevent one breast-cancer death out of 1,000 screened women, but that there was no proof that screening programs affect overall deaths. In other words, echoing the work of scientists like Baines, Miller and Gotzsche, the mantra that “mammography saves lives” is simply not true for most women.

The authors of the New England article concluded: “It is easy to promote mammography screening if the majority of women believe that it prevents or reduces the risk of getting breast cancer and saves many lives through early detection of aggressive tumours. We would be in favour of mammography screening if these beliefs were valid. Unfortunately, they are not, and we believe that women need to be told so.”

But what do Canadians get instead?

The Canadian Breast Cancer Foundation saying we should ignore the science, as they dish out the “Best Health Advice” via an email on a Friday afternoon.


Alan Cassels is a University of Victoria drug-policy researcher and the author of Seeking Sickness: Medical Screening and the Misguided Hunt for Disease.