Breast cancer screening saved my life, is one of the most powerful narratives in modern medicine, if not in Western culture more generally. So no wonder the new Canadian recommendations on screening mammography – suggesting only postmenopausal women undergo the test and do so less often – have sparked anger.

Everyone knows a breast cancer survivor with an inspiring tale, just as everyone knows the mantra, “early detection saves lives.” If only repetition swathed in pink ribbons was all that was required to make it so. All the committee members who produced the new guidelines had to work with was scientific evidence – and the evidence is a lot more equivocal than the anecdote and a lot more convincing than the dire warnings that “thousands will die” if the new recommendations are followed.

The Canadian guidelines would not apply to women who are at high risk (meaning they have a family history of breast cancer or have tested positive for the breast cancer genes BRCA1 or BRCA2). They are similar to those issued by the U.S. Preventive Services Task Force earlier this year. In both countries, annual mammography for all women over 40 was becoming the norm. So why do the experts say that is not a good idea? First and foremost because a growing body of evidence shows that screening is not the lifesaver it is made out to be.