In a newly published paper in the Canadian Medical Association Journal (CMAJ), the Canadian Task Force on Preventive Health Care also discourages doctors from routinely physically examining women for breast cancer. In addition, physicians should advise at average-risk women to not routinely examine themselves for the disease.
“We’ve found that the balance between benefits and harms is not in favour of screening women aged 40-49,” says Michel Joffres, an SFU health scientist and taskforce member. “The final decision though should be left to women after discussion with their physician about these tradeoffs.
“This fits with B.C.’s current policy, which covers screening of women from age 40 but does not systematically target them.
“The taskforce has found regular screening of this group leads to over diagnosis of breast cancer, resulting in unnecessarily heightened patient fear and anxiety. It also leads to unnecessary biopsies, lumpectomies, mastectomies and other interventions.”
However, the authors find the potential benefit-to-harm ratio reverses increasingly in breast cancer-screened women aged 50 and over. They recommend that women aged 50 to 74 at average risk have access to screening every two to three years, rather than every two years as is currently the practice.
The taskforce, re-established by the Public Health Agency of Canada, develops clinical practice guidelines that support primary care providers in delivering preventive health care.
The taskforce’s revamping of federally sanctioned breast cancer screening guidelines appears in the CMAJ-published paper (Nov. 2011) Recommendations on screening for breast cancer in average-risk women aged 40-74 years.
The recommendations are based on an extensive review of thousands of breast cancer screening-related studies, done by a McMaster University-based research group supporting the task force.
The paper’s authors hope governments and policymakers will revise their guidelines accordingly.
Women at average risk are described as those who have no history of breast cancer amongst themselves or in a mother, sister or daughter and no history of chest radiation. They must also not be carriers of the BRCA1 or BRCA2 gene mutations, which greatly increase women’s risk of breast cancer.
British Columbia’s provincial government developed the first organized breast cancer screening program in 1988. It encourages all women aged 40 and older to check their breasts for potentially cancerous tumours, undergo clinical exams and get regular mammograms after age 50 but accepts women from age 40.
The federal government launched the first phase of a nationwide breast-screening program, encouraging the same actions but targeting women 50 and older, in 1992.
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Backgrounder: New breast screening guidelines
Key taskforce recommendations on breast cancer screening:
• The task force recommendations cover the use of mammography, magnetic resonance imaging (MRI), breast self-examination and clinical breast examination to screen for breast cancer.
• The recommendations apply only to women at average-risk of breast cancer aged 40-74. They don’t apply to women at higher risk because of personal history of breast cancer, history of breast cancer in first-degree relatives, known mutations of the BRCA1/BRCA2 genes or previous exposure of the chest wall to radiation.
• No recommendations are made for women aged 75 years and older, given the lack of data available for this group.
• For women aged 40-49, the authors recommend not routinely screening with mammography. For women aged 50-74, the authors recommend routine screening with mammography every two to three years.
• The authors recommend not routinely screening with MRI scans and clinical breast exams alone or in conjunction with mammography.
• For women at average risk who choose to have screening mammography, an interval of every two to three years appears appropriate.
• There is no evidence that screening women at average risk of breast cancer using MRI, clinical breast exams or breast self-exams reduces the risk of mortality or other clinically relevant adverse outcomes.
• One in nine women is expected to develop breast cancer in her lifetime, and one in 29 is expected to die from the disease.
• One study estimates two per 1,000 women carry the BCRA1 mutation, and two per 1,000 carry the BCRA2 mutation.
• From 1982 to 2011 the breast cancer incidence in Canada rose about 20 per cent, adjusting for age. Mortality dropped by about a third.
• The five-year survival rate of breast cancer survivors has risen by about six per cent in the last 16-19 years from 82 to 88 per cent.
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Note: Michel Joffres is in Vancouver Nov. 21/22 but in Victoria after that.