Mammography screening: Weighing the pros and cons for women’s health

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Publication Date: 
Tue, 2012-07-17

But in Canada’s most populous province, Ontario, there are clear incentives to enroll women in screening. Family doctors are eligible for a $2,000 bonus if they enroll 80 per cent of their female patients aged 50 to 69 in a biannual mammography screening program.

One of the architects of Ontario’s performance target bonus system, which was introduced in 2001, is Dr. Ruth Wilson, former president of the College of Family Physicians of Canada.

She says the bonus incentive was based on evidence available at the time—strong evidence to support the benefits of mammography. Since then, there’s been accumulating evidence of harm from mammography.

“I think the performance target will have to change,” she says, adding however that it is difficult to “count or measure” if physicians have discussed pros and cons of a procedure with patients.

Still, new evidence must be taken into account. “Medicine is like that, says Wilson. “Many, many things have changed over the course of my lifetime. Things we fervently thought were right, turned out to be wrong, or things we thought were wrong turned out to be right.”  

In addition to the potential harms outlined earlier, new evidence is emerging that some small cancers, detected only through imaging, regress or disappear on their own.  

For this and other reasons, Dr. Steven Narod, a leading breast cancer researcher, notes that the benefit of screening is “greater for women with [lymph] node positive, than node negative breast cancer.” Node positive indicates that the breast cancer has spread to lymph nodes.  

A pamphlet from the Public Health Agency of Canada notes: “Even though your screening mammogram found breast cancer, your quality of life or the number of years you live may not change. Some breast cancers found by screening would otherwise cause no problems because women would die of something else first. These breast cancers could be slow growing cancers. So, if women with these cancers had not had screening, they might never have known they had cancer and would not have had treatment.”

Still, breast cancer screening programs are well entrenched—in 2008, 72 per cent of women 50 to 69 in Canada reported that they had had a mammogram in the previous two years, according to Statistics Canada.

"I think the public need to recognize that for noble and not-so-noble reasons, the health-care industry is always going to promote more, and the well-meaning will provide more since they are more afraid of missing a case than over finding too many cases,” says Steven Lewis, a health policy consultant and adjunct professor of health policy at Simon Fraser University.

Ann Silversides is an independent journalist and author who specializes in health policy.

Public discussion-debate “Is too much cancer screening hazardous to your health? The example of breast cancer”. A speech by Peter Gøtzsche, researcher and director of the Nordic Cochrane Centre. Published by Prescrire.

Book review of Mammography Screening: Truth, Lies and Controversy (Radcliffe Publishing, London/New York: 2012) by physician and researcher, Peter C. Gøtzsche. Available from the Centers for Medical Consumers website.

The Canadian Task Force on Preventive Health Care intends to create decision aids to help women decide whether or not to have a screening mammogram. In the meantime, two pamphlets to help with this decision making are available: the Public Health Agency of Canada pamphlet and the Cochrane Collaboration pamphlet.

Dr. Susan Love’s Breast Book (2010 edition) has an entire chapter outlining issues concerning breast cancer screening.

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