At what age should mammograms be initiated for women of average risk in Canada?

Breast Cancer Screening Age Recommendations in Canada for Average-Risk Women

Based on the most recent and highest quality evidence, mammography screening for average-risk women in Canada should begin at age 40, not age 45 or 52, to maximize mortality reduction benefits. 1

Current Recommendations by Age Group

Women Age 40-49

• The American College of Radiology (ACR) recommends annual mammographic screening beginning at age 40 for women of average risk 1
• Beginning screening at age 40 rather than 45 or 50 provides greater mortality reduction and allows for earlier diagnosis 1, 2
• Women who begin screening at age 40 are more likely to have early-stage disease, negative lymph nodes, and smaller tumors than unscreened women 2
• Delaying screening until age 45 or 50 results in unnecessary loss of life to breast cancer 2

Women Age 50-74

• Biennial screening mammography is recommended for women aged 50 to 74 years according to some guidelines 1
• However, annual screening results in more screening-detected tumors, smaller tumor sizes, and fewer interval cancers than longer screening intervals 1, 2
• The mortality reduction is greatest for women aged 60-69 years (RR 0.67,95% CI 0.54-0.83), with an estimated 21 deaths prevented per 10,000 women over 10 years 3

Women Age 75 and Older

• Screening should continue past age 74 years without an upper age limit unless severe comorbidities limit life expectancy 2
• Women should continue screening mammography as long as their overall health is good and they have a life expectancy of 10 years or more 1

Benefits of Earlier Screening

• Early detection decreases breast cancer mortality across multiple study designs 1
• Annual screening starting at age 40 provides the greatest mortality reduction, with potential for up to 40% reduction with regular screening 2
• Earlier screening leads to diagnosis at earlier stages, better surgical options, and more effective chemotherapy 2
• Treatment advances cannot overcome the disadvantage of being diagnosed with an advanced-stage tumor 2

Risks and Limitations of Screening

• Risks include increased recall rates, benign biopsies, and psychological effects of false-positive results 4
• Estimates of cumulative lifetime risk of false-positive results are greater if screening begins at younger ages due to greater number of mammograms and higher recall rates in younger women 5
• The quality of evidence for overdiagnosis is not sufficient to estimate lifetime risk with confidence 5

Special Considerations for High-Risk Women

• Women with genetic mutations (BRCA1/2), family history with calculated lifetime risk ≥20%, or history of chest radiation at young age require earlier and more intensive screening 1, 6
• Black women and those of Ashkenazi Jewish descent should be evaluated for breast cancer risk no later than age 30 1, 6
• Women with personal histories of breast cancer, especially those diagnosed by age 50 or with dense tissue, should consider additional surveillance with MRI 1, 6

Screening Technology Considerations

• Digital breast tomosynthesis (DBT) increases cancer detection rates and decreases recall rates compared to standard digital mammography 1
• For high-risk women who cannot undergo MRI, ultrasound should be considered as supplemental screening 6

Canadian Context

• While the Canadian Task Force on Preventive Health Care previously recommended beginning screening at age 50 1, more recent and comprehensive evidence supports earlier initiation of screening at age 40 1, 2
• The historical Canadian position (as of 2001) was that evidence did not conclusively support inclusion or exclusion of mammography for women aged 40-49 4
• However, newer evidence demonstrates that the benefits of starting screening at age 40 outweigh the risks, particularly in terms of mortality reduction 1, 2

Common Pitfalls to Avoid

• Waiting until age 50 to begin screening results in missed opportunities for early detection and treatment 2
• Biennial screening may be less effective than annual screening, particularly for premenopausal women 5
• Stopping screening based solely on age rather than overall health status and life expectancy 1, 2
• Failing to identify and provide enhanced screening for high-risk women 1, 6