Understanding the benefits and harms is key to breast cancer screening

Understanding the benefits and harms is key to breast cancer screening

May 30, 2024

Understanding the benefits and harms is key to breast cancer screening

The Canadian Task Force on Preventive Health Care urges women to ask for the information they need to make the decision about screening that’s right for them.

OTTAWA – Today, the Canadian Task Force on Preventive Health (Task Force) issued updated draft recommendations for breast cancer screening that conclude the harms and benefits should be carefully weighed before deciding on screening.

The Task Force conducted a comprehensive evidence review of more than 165 studies, including recent observational studies, randomized controlled trials, mathematical modelling, data from Statistics Canada and other sources to ensure it had the most recent evidence to inform the draft recommendations. This allowed the group to better understand the benefits of screening. It also underlined that across age groups, additional imaging, unnecessary biopsies, and overdiagnoses carry enough potential risk that they should be carefully considered before undergoing breast cancer screening.

The updated draft recommendations also state that if someone aged 40 to 74 chooses to be screened after understanding the benefits and harms, mammography should be accessible every two to three years. They apply to women (people assigned female at birth) 40 years of age and over at average or moderately increased risk**.

The recommendations do not apply to those with a personal or extensive family history of breast cancer or genetic mutations that would increase breast cancer risk. They also do not apply to individuals who have symptoms, such as a lump, those who feel they may be at high risk and those who are transgender women.

These individuals should consult a healthcare provider about appropriate options.

“We all want to find ways to reduce the burden of this disease and improve outcomes,” said Dr. Guylène Thériault, a family physician, teacher of evidence-based medicine and chair of the Task Force and breast cancer working group. “People may find that information about breast cancer screening is surprising – there are potential benefits to screening, but there are also harms. We want women to have all the information they need to make the decision that’s right for them.”

The guideline working group included 4 breast cancer content experts – a medical oncologist, radiation oncologist, surgical oncologist and radiologist – three patient partners, as well as family physicians, a nurse practitioner, evidence review teams and other experts.

“As clinicians who see patients with breast cancer, we understand the value that patients and their families place on screening,” says Dr. Henry Siu, a family physician and Task Force member. “At the same time, we could not ignore the story that the current evidence shows about the effect of screening on reducing breast cancer death. As a family physician, my job is to help patients understand their individual balance of benefits and harms of breast cancer screening when deciding whether screening is right for them.”

As part of the evidence review, the Task Force conducted a systematic review of patient values and preferences for breast cancer screening which showed that a majority of patients aged 40-49 might not think the benefits outweigh the harms.

“Our comprehensive evidence review showed a smaller benefit in women 40 to 49 compared to older ages, and there are also harms,” said Nathalie Slavtcheva, a nurse practitioner and working group co-chair. “There was also variability in what women would choose to do if they were given information about benefits and harms of screening.”

“It is important to underscore that if someone has a symptom like a lump, they should talk to a health care provider. That is not screening but rather diagnosis,” says Dr. Thériault.

The recommendations differ from those in the United States, in part, because of differences in populations and healthcare systems. The Task Force is not making specific recommendations around Black and racialized populations, and recommends against supplementary screening for dense breasts, as there is insufficient evidence.

“We join the United States Preventive Services Task Force in calling for more research on the impact of screening in Black and other racialized populations, and more research on supplemental screening for those with dense breasts,” said Dr. Eddy Lang, an emergency physician at the University of Calgary and a Task Force member.

“The key takeaway is for people to get the facts and make the choice that’s right for them,” said Dr. Kate Miller, a family physician and Task Force member. “Talk to your health care provider about what’s right for you or use the tools on our website to get informed about both the benefits and harms. Breast cancer is a risk for anyone assigned female at birth including women, trans men who have not had a double mastectomy and non-binary individuals. Everyone should have access to both the information they need and access to mammography screening if they decide it is right for them.”

The draft recommendations and patient and clinician decision-making tools are available at  https://canadiantaskforce.ca/public/. They will be open for 6 weeks of public comment beginning May 30.

Download media kit HERE.

Media contact for interviews:
Kim Barnhardt, Communications, media@canadiantaskforce.ca

**Moderately increased risk: People with dense breast category C or D or moderate family history (no more than one first degree or two second degree relatives diagnosed after 50). Learn more.