The updated 2018 Canadian Task Force on Preventive Health Care breast cancer screening guidelines for average risk women is a welcome change from the more paternalistic guidelines that we as family doctors receive on a regular basis.
The updated guidelines follow a trend of engaging patients in shared decision making. What we call “patient-centred care.” Patient-centred care encourages patients to feel that they are being treated as a whole person by ensuring that the health care they receive reflects their own values and preferences.
When breast cancer screening task forces in Canada and around the world review years of rigorous studies, they continue to see a small benefit of saving women aged 40 to 74 years from dying of breast cancer. This benefit is smaller in women under the age of 50 compared to women over 50 years.
To give you a sense of the difference between age groups, it is estimated that if you take 1,000 women in each age group and look at death from breast cancer, screening mammograms will save two lives in women aged 70 to 74, one life in women aged 50 to 69 and less than one life in women 40 to 49 years of age.
Unintended risks are also seen in these studies. This includes physical and psychological consequences from false positive results as well as overdiagnosis resulting in unnecessary treatment of cancer that would not have caused harm in a woman’s lifetime.
Women less than 50 years of age have a higher risk of these harms than older women. As an example, it is estimated that if you take 1,000 women in each age group, screening mammograms will cause unnecessary biopsies in 30 women aged 70 to 74, in 35 women aged 60 to 69, in 37 women aged 50 to 59 and 43 in women aged 40 to 49.
Based on this information, the current 2018 recommendations for average risk women have not changed much compared to the 2011 guidelines.
For women aged 40 to 49 years, screening with mammography is not recommended. For women aged 50 to 74 years, screening with mammography every two to three years is recommended.
While the recommendations seem reasonable for large populations of women, they don’t factor in that individual women may want to make their own decisions on whether or not they are willing to accept certain risks (including the anxiety associated with false positive results, potentially unnecessary biopsies and the potential for overdiagnosis) over a gain of a small potential benefit of not dying from breast cancer.For the 2018 updated guidelines, the task force also looked at the results from 29 studies that explored how women 40 years of age and older rated the importance of their own personal expected benefits and harms of breast cancer screening.
This review of patient values and preferences suggested that many women aged 40 to 49 years would not choose to undergo breast cancer screening using mammography if they were aware of the risks commonly seen among women in their age group.
In contrast, many women aged 50 years and older chose screening given their more favourable balance of benefits and harms. This led the task force to add to the 2018 updated recommendations, “the decision to undergo screening is conditional on the relative value a woman places on possible benefits and harms from screening.”
For women who are at high risk, obviously it is a different discussion. Similarly, if women of any age have any signs or symptoms of breast cancer, such as nipple discharge, lumps, puckering, dimpling, or skin changes of the breast they should see their family doctor to discuss a diagnostic mammogram.
As advances in breast cancer screening, diagnosis and management emerge, we hope to see significantly less of the risks associated with mammograms in women who do not have breast cancer as well as less overdiagnosis and treatment of breast cancers that would have never caused a problem.
Until then we need to get away from the one-size-fits-all recommendations and move toward a more personalized shared decision-making approach to help women decide if a screening mammogram is right for them. In practice, I still recommend screening mammograms for most women over age 50 and even for some women under 50.