054 Canadian task force on preventive health care’s breast cancer screening guideline: collision of evidence, advocacy and politics

In May 2023, the Canadian Task Force on Preventive Health Care (Task Force) was requested to undertake an expedited update of its 2018 guideline on breast cancer screening. The request was triggered by the release of the United States Preventive Services Task Force recommendations that supported screening in individuals 40–49 years. The expedited review was further pressured as a result of advocacy campaigns and political interference, which persisted during development and after release of the draft guideline update in May 2024. Attempts to thwart the independence of the Task Force’s work were evident as specific patient advocacy groups, long-standing professional advocates and newly formed radiologist-led associations sought to influence the review, and even to disband the Task Force. Political interference was manifested by: 1) an inflammatory and inaccurate media briefing by the Minister of Health on the day of the draft guideline’s release; 2) the convening of parliamentary committees on breast cancer screening where invited speakers were almost exclusively pro-screening; 3) the initiation of an external review from which the Task Force was almost entirely excluded, and; 4) attempts at on-going interference by the Minister of Health on the progress of the guideline. Throughout this offensive, it was clear to the Task Force that most detractors were uneducated on the methods used for the extensive, publicly available evidence reviews and the rationales behind the recommendations. Alternatively, some simply did not believe the evidence. Common themes encountered were: 1) more screening is better, 2) earlier screening is better, 3) increasing breast cancer incidence justifies more and earlier screening, 4) harms from screening are overstated, 5) more screening is justified even/especially in the absence of research. The extent of overdiagnosis was minimized, and denigrated. Overdiagnosis did not resonate with the public or parliamentarians, quite possibly because they did not want to believe. We encountered fixed, false beliefs among advocates that were exploited for political and other purposes. In developing guideline recommendations, particularly on cancer screening, these types of experiences are not unique to the Canadian Task Force. The United States Preventive Services Task Force encountered similar tactics in years past, particularly on breast cancer screening. Comprehensive, high quality methods for guidelines help but may be unable to overcome populist ideas and personal narratives. We will discuss lessons-learned to help better support work on evidence-based screening and preventive health care guidelines in the future. In particular, we will consider how evidence-based messages that do not increase overdiagnosis is heard and followed. We will share insights from our experience. Objectives Describe the intersection of evidence, advocacy, and politics encountered during the development of the Canadian Task Force on Preventive Health Care’s updated 2025 breast cancer screening guidelines. Discuss how comprehensive, high-quality, evidence-based methods are helpful but may be insufficient to be overcome advocates’ narratives; benefits tend to be inflated while harms from false positives and overdiagnosis are minimized. Describe common themes/beliefs held by breast cancer screening proponents such as: more screening is better, earlier screening is better, increasing incidence is sufficient for more screening, harms from screening are overstated, more screening is justified in the absence of research. Discuss possible opportunities and barriers encountered when evidence is at odds with belief and political expediency. Seminar: In May 2023, the Canadian Task Force on Preventive Health Care (Task Force) was requested to undertake an expedited update of its 2018 guideline on breast cancer screening. In this seminar, we will review the collision of evidence, advocacy and politics that we encountered, and engage with the audience in a discussion to explore some possible paths forward. Please also see abstract & objectives. Results The Canadian Task Force on Preventive Health Care encountered a hostile intersection of evidence, advocacy, and politics during the development of its updated 2025 breast cancer screening guidelines. It was clear to the Task Force that most detractors were uneducated on the methods used for the extensive, publicly available evidence reviews and the rationales behind the recommendations. Political interference was manifested in several ways, posing a threat to the independence of the Task Force. High-quality, evidence-based methods were helpful but may be insufficient to overcome advocates’ narratives, or evidence may simply not be believed. Some common themes/beliefs were identified among breast cancer screening proponents such as: more screening is better, earlier screening is better, increasing incidence is sufficient for more screening, harms from screening are overstated, more screening is justified in the absence of research. The experience and progress to date will be discussed. Also see abstract & objectives. Conclusions In developing guideline recommendations, particularly on cancer screening, the collision of evidence, advocacy and politics may be increasingly common. Comprehensive, high quality methods for guidelines help but may be unable to overcome populist ideas. We will discuss lessons-learned to support the work on evidence-based screening and preventive health care guidelines in the future. In particular, what can be done to ensure that an evidence-based message that does not increase overdiagnosis is heard and followed?

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