Mammograms for women in 40s: Now Canada recommends against them

Should women age 40-49 who are at regular risk of breast cancer get routine mammograms? A Canadian task force recommends no, just as the United States Preventive Services Task Force did in 2009 (for which it caught plenty of heat).

The Canadian recommendations are the first update since 2001 for women of average risk of breast cancer. “Average risk” means women who’ve not had breast cancer in the past, don’t have risk-increasing mutations in their BRCA genes and have no family history of breast cancer in a mother, sister or daughter.

Just as the U.S. task force did, our neighbors to the north recommended against routine screens in the 40-49 age group because in their assessment of the evidence -- on a population level -- the risks of harm from screening mammograms in this age class outweigh the benefits. The new recommendations were just published in the Canadian Medical Assn. Journal.

Here’s what they say, and their reasoning.

Women of average risk age 40-49: no routine mammogram screening.

The task force notes that breast cancer is a lot rarer in this age group -- and that in order to save one death from breast cancer, you’d have to screen more than 2,000 women once every 2-3 years for 11 years.

Among that group, 690 women will receive a false positive on a mammogram, 75 women will have an unnecessary biopsy. Among all women 40 and older (not just 40-49, because they didn’t have good numbers on that group), they note about 5 in 1,000 screened will have unnecessary lumpectomies or mastectomies.


The task force also mentions distress as a factor in their conclusion that “this ratio of potential benefit to harm does not justify routine screening in women aged 40-49 years.”

But the task force also notes that some lives are saved, and that doctors and patients talk clearly through the benefits and harm that screening poses.

Women age 50-74: Instead of a mammogram every two years (currently the recommendation in Canada), screening should be done every 2-3 years.

Other recommendations: The task force also recommends against MRIs for women of average risk and also against routine breast self-exams and clinical breast exams in women with no symptoms. (There’s no evidence that these things help to reduce death and other medical harms, they say.)

The breast self-exam may be deemed empowering and important by some groups but in fact a lot of breast cancer experts have long been on the fence about it. (Read what the National Cancer Institute says.) The U.S. Preventive Services Task Force also recommended against teaching breast self-exams in 2009.

Here is a link to the new Canadian guidelines in more detail.

And here’s a commentary about them.

Finally, here’s the U.S. Preventive Services Task Force report of 2009 that stoked a whole mess of controversy in this country.