In December 2018, the Canadian Task Force on Preventive Health Care updated its recommendations for breast screening of average-risk women.
While still recommending that women 50-74 have mammography screening every 2-3 years, it is now conditional on women’s informed decision-making based on their assessment of harms and benefits.
It is not a strong recommendation.
They state there is very low certainty evidence of a modest breast cancer mortality reduction. Many other major studies have found that mammography screening does not reduce the death rate among screened women overall.
This is very important as it is widely promoted that mammography screening saves lives — it does not.
This is difficult for women (and others) to hear.
It is also true that it does not result in fewer advanced breast cancers being diagnosed or in less aggressive treatment.
It is important that harms of mammography screening are considered including over diagnosis (‘cancers’ that would not have been found if not for screening nor caused harm in a woman’s lifetime), false positives leading to biopsies, radiation, and the associated anxiety.
The task force considered the preferences of women regarding mammography screening but noted the studies they reviewed “tended to provide high benefit-to-harm ratios.”
They call for more studies of women’s preferences using “accurate estimates of both benefits and harms” — in other words that are not biased.
It is not easy for women to make an informed decision regarding mammography screening — nor for primary care providers to help them to do so.
The evidence is vast and complex.
The task force recommendations are a major step forward for women’s health but I hope their next recommendations will unequivocally recommend against mammography screening for average-risk women of any age and will consider cost effectiveness.
In the meantime, women should examine their breasts and primary care providers should examine women’s breasts — there just isn’t sufficient evidence to not do so.
Professor, Faculty of Nursing