Question Period Note: Canadian Task Force on Preventive Health Care's Breast Cancer Screening Guideline

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In 2018, the Canadian Task Force on Preventive Health Care (“Task Force”) published “Recommendations on screening for breast cancer in women 40-74 years of age who are not at increased risk for breast cancer” in the Canadian Medical Association Journal. This guideline was an update to the Task Force recommendations on breast cancer screening from 2011. Since 2018, advocacy groups and a small number of medical imaging researchers have contested various aspects of the guideline in the media, academic literature and in correspondence to the Public Health Agency of Canada (PHAC) and Health Canada.

On May 9, 2023, the U.S. Preventive Services Task Force issued a draft recommendation statement on breast cancer screening, which includes lowering the age of screening initiation from 50 to 40. Differences between this new guideline and current Canadian guidelines from the Canadian Task Force on Preventive Healthcare are anticipated to generate stakeholder and media interest.
Key Messages
• We recognize that breast cancer is a major health issue. It is the most commonly diagnosed cancer and the second leading cause of cancer death in Canadian women.
• The Canadian Task Force on Preventive Health Care develops their guidelines based on the best available scientific evidence and other considerations, such as patients’ values and preferences.
• The Task Force’s current guideline on breast cancer screening outlines both the benefits and harms of screening for Canadian women and stresses the importance of shared decision-making between women and their healthcare providers to support an informed decision.
• The Government of Canada has pledged up to $500,000 in additional funding to help the Task Force expedite updates to their guideline on breast cancer screening to ensure that they remain reflective of the best available evidence.
• In addition, the Public Health Agency of Canada intends to host a knowledge exchange event in September to bring together experts, partners, those with lived experiences, and other stakeholders, to discuss the current state of the science, including knowledge gaps, related to breast cancer screening.

If pressed on the withdrawal of support from the Canadian Cancer Society:
• We are aware that some stakeholder groups, including the Canadian Cancer Society, have been in contact with the Task Force regarding the update of their 2018 guideline.
• The Task Force responds to inquiries about their guidelines, and it is my understanding they have followed up with these stakeholders.

If pressed on the Government of Canada’s evaluation of the Canadian Task Force on Preventive Health Care
• The Public Health Agency of Canada has undertaken an evaluation of the Task Force’s expertise, methodology, governance, and funding mechanisms as well as the effectiveness of its knowledge translation activities. The results of the evaluation are publicly available.
• All Agency programs are routinely evaluated in this manner.

If pressed on the updated recommendations from the United States Preventive Services Task Force
• The Task Force is aware of the updated U.S. recommendations and will be examining them closely as they update their existing recommendations.

The Canadian Task Force on Preventive Health Care (Task Force) is an independent arms-length body of up to 15 clinicians and methodologists established and funded by the Public Health Agency of Canada (PHAC). The Task Force has developed evidence-based clinical practice guidelines on a range of topics that support primary care providers in the delivery of preventive healthcare.

PHAC’s role in the production of guidelines is to ensure rigorous and appropriate methods are used to analyze the scientific evidence that forms the basis for the independent recommendations made by the Task Force. PHAC scientific staff members are authors on Task Force guidelines but do not vote on nor endorse the recommendations.

Task Force Recommendations
Recommendations from the Task Force’s guideline apply to women aged 40 to 74 years not at increased risk of breast cancer, with the decision to undergo screening for each age group conditional on the relative value a woman places on possible benefits and harms from screening:
• For women aged 40 to 49 years – do not screen with mammography.
• For women aged 50 to 69 years – screen with mammography every two to three years.
• For women aged 70 to 74 years – screen with mammography every two to three years.

These recommendations are consistent with the Task Force’s previous recommendations and those in the United Kingdom and Australia.

On May 9, 2023, the United States Preventive Services Task Force published a draft update to their 2016 recommendations. Their previous 2016 guideline aligned with the Canadian Task Force’s guidance of 2018. The updated recommendation, which was subject to public comment until June 5, lowers the age of first screening from 50 to 40. The change from age 50 to age 40 was based on trends in rates of breast cancer in this age group over time in the U.S. It is also based on formal modelling commissioned for this guideline which indicated a small potential benefit for women in this age (1.3 additional breast cancer deaths averted per 1,000 women screened beginning at 40 compared to starting at 50). They also examined randomized controlled trials and observational studies but did not identify any that provided additional evidence for screening in this age group. They also concluded there is insufficient evidence to recommend for or against screening above the age of 74, or additional screening (e.g., ultrasound or MRI) for women with dense breasts.

Federal/Provincial/Territorial and Stakeholder Considerations
Presently, the majority of provincial and territorial screening programs operate in adherence to the Task Force’s guideline. However, Alberta, updated their screening guidelines in 2022, reducing the age for screening to 45 from 50. This was based on their local epidemiological data as well as modeling. Several provinces do permit screening earlier based on a care provider’s referral or self-referral.

Many stakeholders are supportive of the guideline, including the College of Family Physicians of Canada, and the Nurse Practitioners’ Association of Canada. In late 2022, the Canadian Partnership Against Cancer and the Canadian Cancer Society withdrew their support for the 2018 guideline and called on the Task Force to undertake a review of this guideline.

Since the release of the guideline, some advocacy groups have publicly expressed concerns about several aspects of the guideline, including the age to screen, that it does not include recommendations on supplemental screening for women with dense breast tissue, and that it recommends against breast self-exams.

In late 2021, this group undertook a campaign to allege misconduct in the Canadian National Breast Screening Study (CNBSS), which has been used to inform breast cancer screening guidance in Canada and internationally, in academic and other forms of media. The study considered flawed by these advocacy groups is one of eight key trials included in the Task Force guideline. A 2023 study examined the impact of removing this study from the evidence base and concluded that this would not have an impact on the overall results of the evidence review that informed the Task Force guideline.

In late 2022 these groups began a letter-writing campaign to MPs regarding the Task Force guidelines, indicating that they are flawed and ignore current evidence. The letter calls on MPs to immediately suspend the use of the current Task Force guidelines and create a new panel with breast cancer specialists to make guidelines. A number of these have been forwarded to the Minister of Health and a standard response has been prepared.

In response to stakeholder concerns regarding the lack of recent high-quality evidence to inform screening recommendations, PHAC collaborated with the Canadian Institutes of Health Research (CIHR) to host a Best Brains Exchange (BBE) on advancing the research agenda on breast cancer screening in 2021. This event provided an opportunity for approximately 50 researchers and implementation experts, policy makers, health research funders and other key stakeholders to discuss the current state of the evidence, including knowledge gaps related to breast cancer screening. A report summarizing the BBE (presentation, discussions, and research gaps identified) was shared with BBE attendees, including key stakeholders such as the Canadian Cancer Society and the Canadian Partnership Against Cancer, in October 2021. BBE attendees have been encouraged to review the research gaps identified during the BBE, and to assess whether their organization can play a role in addressing these gaps. In October 2021, Rethink Breast Cancer, the Canadian Breast Cancer Network and the Canadian Cancer Society announced they would be collaborating to gather the best available evidence to help build an understanding of the impact and effectiveness of the current breast cancer screening guidelines through a real-world evidence review. In 2022 this same group of organizations called upon the Task Force “to review and examine all new and available evidence on breast cancer screening to determine if any changes or updates to the current guidelines should be made.”

The Task Force made the decision to update their 2018 guideline in early 2023 prior to the release of the U.S. Preventive Services Task Force updated guideline. On June 7, 2023, the Task Force publicly announced that it will be conducting an expedited review and update of its 2018 breast screening guideline. They anticipate having a draft of the updated guidance in late fall 2023. On June 8, the Government of Canada announced up to $500,000 in additional funding for the Task Force to help with the expedited timeline for this project.

On June 8, 2023, PHAC announced that it intends to host a knowledge exchange event to bring together experts, partners, those with lived experiences, and stakeholders, to discuss the current state of the science, including knowledge gaps, related to breast cancer screening.
 

• In 2020, an estimated 27,400 women were diagnosed with breast cancer and 5,100 died from the disease. One in eight (12%) women in Canada is expected to be diagnosed with breast cancer in their lifetime.
• The current Task Force guideline on breast cancer screening has been critiqued by a small number of vocal stakeholders since its publication in 2018.
• External evaluations of the Task Force’s 2018 breast cancer guideline by the American College of Physicians in 2019, and independent researchers in 2022, rank the guideline amongst the highest quality in the world.
• The Task Force initiated an update of the 2018 guideline on an expedited basis.