Canadian Task Force Updates Breast Cancer Screening Guidelines

MedicalResearch.com Interview with:

Dr. Ainsley Moore MD, CFPC, MSc(HB), MSc(CLinEpi) Cand
Associate Professor,McMaster University
Associate Editor,Canadian Medical Education Journal
Vice-Chairof the Canadian Task Force on Preventive Health Care
Dr. Moore

Dr. Ainsley Moore MD, CFPC, MSc(HB), MSc(CLinEpi) Cand
Associate Professor,McMaster University
Associate Editor,Canadian Medical Education Journal
Vice-Chair,  Canadian Task Force on Preventive Health Care

MedicalResearch.com:  What is the background for this study?

Response: The Canadian Task Force for Preventive Health Care has updated its Breast Cancer Screening Guideline. It places an emphasis on shared decision-making between women and their health care provider so that women can make an informed decision based on how they prioritize the benefits and harms of screening with mammography.  

Screening may identify breast cancer earlier and lead to a reduction in breast cancer mortality; however, i talso has known harms such as false positive results, further testing including biopsy, and over diagnosis leading to unnecessary treatment with associated complications.

MedicalResearch.com: What are the main findings?

Response: An updated review of the evidence continues to show a close balance between potential benefits and harms of breast cancer screening; this balance appears to be less favourable for younger women than for women aged 50 to 74 years.

A separate review conducted for this guideline on women’s values and preferences about mammography screening suggests that many women aged 40 to 49 years would choose not to be screened if they were aware of the outcomes for their age group. On the other hand, women aged 50 to 74 years are more likely to choose screening given their more favourable balance of benefits and harms

The recommendations:

  • The TaskForce provides conditional recommendations against screening women age 40 to49 years who are not at increased risk of breast cancer, low certainty evidence shows a small potential reduction in breast cancer death along with higher risk of harms including false positive results, further testing including possible breast biopsy and overdiagnosis leading to unnecessary treatment with associated complications. Recommendations are conditional upon how an individual woman from this age group weighs the benefits and harms of screening
  • The TaskForce provides conditional recommendations in favour of screening women aged 50 to 74 years who are not at increased risk of breast cancer, very low-certainty evidence suggests a modest reduction in risk of breast cancer death and, while the risk of harms of screening are lower than for younger women, it remains a concern.  Recommendations are conditional upon who an individual woman of this age group weighs the benefits and harms of screening

MedicalResearch.com: What should readers take away from your report?

Response: The Task Force provides information on the benefits and harms of breast cancer screening and has developed tools on their website to help guide the discussion between women and their health care provider so that they can make the decision that is best for themFor more details on the Task Force’s findings and recommendations and patient tools, please visit: canadiantaskforce.ca

MedicalResearch.com: What recommendations do you have for future research as a result of this work?

Response: More and better-quality evidence is needed on the impact of breast cancer screening for women of all ages.  Additional studies on Canadian women’s values and preferences for screening that are based on accurate estimates of both benefits and harms conducted in a transparent and easily comparable manner would assist in guiding future recommendations.

MedicalResearch.com: Is there anything else you would like to add?

Response: The Public Health Agency of Canada established theCanadian Task Force for Preventive Health Care to make recommendations forCanadian primary care providers on a broad array of preventive health issues.The members of the Task Force were selected for their expertise in Preventive health care delivered in primary care settings. Task Force members adhere to the highest ethical standards including the avoidance of professional conflicts of interest in order to ensure the scientific credibility of its recommendations.

Citation:

Recommendations on screening for breast cancer in women aged 40–74 years who are not at increased risk for breast cancer

Scott Klarenbach, Nicki Sims-Jones, Gabriela Lewin, Harminder Singh, Guylène Thériault, Marcello Tonelli, Marion Doull, Susan Courage, Alejandra Jaramillo Garcia and Brett D. Thombs; for the Canadian Task Force on Preventive Health Care

CMAJ December 10,2018 190 (49) E1441-E1451; DOI:https://doi.org/10.1503/cmaj.180463

[last-modified]

The information onMedicalResearch.com is provided for educational purposes only, and is in no way intended to diagnose, cure, or treat any medical or other condition. Always seek the advice of your physician or other qualified health and ask your doctor any questions you may have regarding a medical condition. In addition to all other limitations and disclaimers in this agreement, service provider and its third party providers disclaim any liability or loss in connection with the content provided on this website.

1 thought on “Canadian Task Force Updates Breast Cancer Screening Guidelines

  1. Canadian women should be outraged. Today, the Canadian Task Force on Preventive Health (CTF) released its latest guidelines for screening for breast cancer for women at average risk. They advise against mammography for women aged 40-49, against women doing breast self-examination (BSE), and against doctors doing breast exams. They recommend women age 50-74 have mammograms every 2-3 years.

    A 2014 study of screening in Canada showed 40% fewer deaths among women who had screening mammograms than women who didn’t, but the CTF deliberately chose to ignore observational studies done with modern mammography equipment, in favour of Randomized Control Trials (RCTs) from the 1960’s to 1990’s, which show only a 15-20% mortality reduction.

    The only measurable outcome of a RCT is how many women die of breast cancer, so the CTF ignores three other significant benefits of early detection of cancer: the ability to avoid mastectomy, lymphedema and chemotherapy.

    How can the CTF not recommend annual mammography starting at age 40, if it saves the most lives, and allows more women to have less aggressive treatment? The answer is they focus on “harms”: the number of women who are recalled for additional tests after screening, and “overdiagnosis.”

    About 10% of women need additional tests after screening. The CTF uses the pejorative term, “false positive.” That term implies that a cancer was diagnosed, when none was present. This is not the case: women are recalled when there is a potential cancer. This causes anxiety for many women, but it’s transient, and studies show that it doesn’t harm women long-term.

    The CTF gives undue weight to overdiagnosis in the harms-to-benefit discussion. Overdiagnosis is the theoretical possibility that a woman will be diagnosed with breast cancer and treated for it, but die of something else (like a heart attack) before she would have died of cancer. The rate of overdiagnosis can only be estimated. Experts estimate it at 10% or less.
    The CTF says that most women age 40-49 would choose not to be screened. From my thousands of conversations with women during my career, when told that mammograms can prevent breast cancer death, and allow them to have a lumpectomy and avoid chemotherapy if cancer is detected early, most women choose to be screened.

    The CTF calls breast density an emerging issue. We’ve known about it for 40 years! Having dense breasts is a higher risk than having a mother or sister with breast cancer. Mammography is 96% sensitive in fatty breasts but only about 50% sensitive in the densest breasts. And when cancers go undetected by mammography, they grow larger and can spread by the time they are found. The CTF has not acknowledged the harm of not offering supplementary screening for women with dense breasts.

    The CTF says there’s insufficient evidence to recommend supplementary screening for women with dense breasts because of their insistence on RCTs. An RCT of screening ultrasound is underway in Japan but it will take at least 7-10 years before it can prove mortality reduction. We have observational data from multiple studies showing that ultrasound finds an additional 3-4 cancers per thousand women. Finding these cancers earlier will allow less aggressive treatment AND reduce mortality. With convincing observational data available, women shouldn’t have to keep dying prematurely until the Japanese RCT is complete.

    The CTF exaggerates the “harms” of screening, but they don’t mention the harms of not screening. In Canada approximately 4,000 more woman can be expected to die of breast cancer in the next decade, if the CTF guidelines are followed, rather than starting screening at age 40.

    The CTF refuses to consider evidence other than RCTs. The Canadian taxpayer is funding this misadventure that will lead to loss of life, and unnecessary suffering for women who develop breast cancer and are denied early diagnoses when cancers are small, confined to the breast, and most successfully treated.

    Annual mammographic screening starting at age 40 saves the most lives, albeit with inconvenience and stress of recalls and the theoretical possibility of overdiagnosis. Supplementary screening for women with dense breasts can detect early cancers missed on mammography, saving more lives. All women and their family doctors deserve to have all the facts, and the option of shared decision-making, to decide whether the harms outweigh the real benefits. Instead of protecting women from screening, it’s time to start saving women’s lives.

Leave a Reply

Your email address will not be published.

This site uses Akismet to reduce spam. Learn how your comment data is processed.