Breast cancer screening: New emphasis on shared decision-making between women and their doctors

An updated guideline on screening for breast cancer emphasizes shared decision-making between women and their doctors, supporting women to make an informed decision based on personal preferences when the balance between benefits and harms is uncertain. The guideline, released by the Canadian Task Force on Preventive Health Care, is published in CMAJ (Canadian Medical Association Journal).

Based on the latest evidence, including 29 studies assessing the value women place on anticipated benefits and harms from breast cancer screening, the guideline contains recommendations for women aged 40 to 74 years who are not at increased risk of breast cancer.

"Women have different values and preferences when it comes to balancing the benefits and harms of breast cancer screening," says Dr. Ainsley Moore vice-chair of the task force. "Those who may be concerned about the harms of screening, including overdiagnosis and invasive procedures, may choose not to be screened."

Breast cancer screening with mammography may reduce death from breast cancer, although it can also result in false positives, additional testing and possibly invasive procedures, as well as overdiagnosis, overtreatment and potential complications. Current evidence indicates a close balance between benefits and harms, leading to conditional recommendations based on patient preferences.

Recommendations:

• The task force recommends against screening women aged 40 to 49 years. This recommendation is conditional on the relative value a woman places on possible benefits and harms from screening. If women of this age prefer to be screened, they are encouraged to discuss options with their health care provider. Women in this age group face a higher risk of potential harms from false positives, overdiagnosis and overtreatment compared with other age groups, and the absolute benefit is smaller.
• The task force recommends in favour of screening women aged 50 to 74 years with mammography every 2-3 years. This recommendation is also conditional as some women may choose not to be screened if they are concerned about overdiagnosis and the associated harms. The benefits of screening are from very low-certainty evidence indicating a modest reduction in the risk of death from breast cancer.
• The task force recommends against screening with magnetic resonance imaging, tomosynthesis and ultrasonography in women not at high risk based on a lack of evidence.

These recommendations are similar to those from the recent US Preventive Services Task Force guideline as well as the Canadian task force's 2011 guideline.

"These recommendations reflect the growing importance of shared decision-making between patients and physicians in preventive health screening, especially in situations like this where the balance between potential benefits and harms is uncertain," says Dr. Donna Reynolds, member of the task force. "While screening is recommended for women aged 50-74, some may choose not to be screened after weighing the benefits and harms with their physicians, and, conversely, some women under age 50 may choose screening."

The task force is an independent group of primary care and prevention specialists from across Canada. It notes that more high-quality evidence is needed on the benefits of breast cancer screening of women in all age groups.

"We hope this updated guideline will help women in Canada who are not at high risk of breast cancer make the right decision to be screened or not to screen," says Dr. Moore.

In a related commentary, Dr. Deborah Korenstein, Memorial Sloan Kettering Cancer Center and Weill Cornell Medical College, New York, writes, "The new recommendations on breast cancer screening from the Canadian Task Force on Preventive Health Care serve as a model for the important role of guidelines in promoting value in health care."

Dr. Korenstein says that, compared with other international guidelines, the task force's guideline "is alone among similar guidelines in noting in the main recommendation for all age groups that 'the decision to undergo screening is conditional on the relative value that a woman places on possible benefits and harms.' This overt across-the-board acknowledgement of the primacy of the patient world view encourages Canadian physicians to prioritize patient-centred care and value."

For the full guideline and additional patient and physician decision-making tools, visit http://www.canadiantaskforce.ca.

"Recommendations on screening for breast cancer in women aged 40-74 years who are not at increased risk for breast cancer" is published December 10, 2018.