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New breast cancer screening guidelines for women at average risk

Nov. 21, 2011

By Maria Serraino

New recommendations on screening for breast cancer in average-risk women aged 40 to 74 have been published in the CMAJ. The guidelines, updated by the Canadian Task Force on Preventive Health Care issues, recommend no routine mammography screening for women aged 40 to 49 and extend the screening interval from every two years  – which is current practice – to every two to three years for women aged 50 to 74. The guidelines also recommend against routine clinical breast exams and breast self-exams.

According to background information in the study, 80 per cent of newly diagnosed cases of breast cancer in Canada occurred in women over the age of 50, and 28 per cent occurred in women aged 70 and older. Regular screening for breast cancer with mammography, breast self-exams and clinical breast exams are widely recommended to reduce mortality, however controversy remains over which screening services should be provided and to whom.

The clinicians of the task force explain that outcomes of breast cancer screening such as tumour detection and mortality must be put into context of the harms and costs associated with false-positive tests, overdiagnosis and overtreatment. Any positive test result can have a significant emotional impact and financial cost to the patient.

This is the first update to the guidelines since 2001. The updates reflect the latest scientific evidence in screening for breast cancer, and are aimed at informing physicians and policy-makers. The new recommendations are based on randomized and quasi-randomized controlled trials, and target average-risk women in three age groups (40 to 49, 50 to 69 and 70 to 74). Average risk is defined as having no previous breast cancer; no history of breast cancer in a mother, sister or daughter; no known gene mutations and/or no previous exposure of the chest wall to radiation.

Key recommendations:

  • Mammography:
    • for women aged 40 to 49 no routine mammography is recommended, because cancer risk is low, and the risk of false-positive results, overdiagnosis and overtreatment is high
    • for women aged 50 to 59 routine mammography is recommended every two to three years because the absolute benefits remain small and false-positive results and unnecessary invasive investigation is high
    • for women aged 70 to 74 routine mammography every two to three years is recommended because mammography does not significantly reduce the relative risk of death from breast cancer in this age group
  • MRI
    • No screening of average-risk women using MRI is recommended. However there are no data evaluating whether screening women using MRI scans reduces mortality compared with mammography or no screening.
  • Clinical breast exam and breast self-exam
    • No routine clinical breast exams or breast self-exams are recommended. Available evidence does not support the use of clinical breast exams or self-exams to screen for breast cancer among women at average risk.  

The guidelines are intended to inform physicians and clinicians. Women are encouraged to discuss the risks and benefits of screening with their doctor to determine the best approach for them.

The Canadian Task Force on Preventive Health Care explains that more research needs to be done on the harms and benefits of screening using mammography for women younger than 40 years and older than 74.

The findings suggest that although screening may permit surgery for breast cancer at an earlier stage and reduce mortality from breast cancer among women aged 40 to 74, the absolute benefit is small and partially offset by harms caused by unnecessary intervention. It is recommended that doctors and patients discuss the balance of benefits and harms of any screening prior to making a decision.

The study appears in the Nov. 21 issue of CMAJ


Read more on breast cancer:

Women's College Spirit of Discovery: Breast Cancer

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  • A publication of:
  • Women's College Hospital