What are the current guidelines for when to start breast cancer screening with mammography (mammogram)?

Current Canadian Guidelines for Breast Cancer Screening

The Canadian guidelines recommend that women at average risk should begin regular mammography screening at age 45 years, with annual screening between ages 45-54, and biennial screening at age 55 and older as long as overall health is good and life expectancy is 10 years or more.

Screening Recommendations by Age Group

Women Ages 40-44

• Women should have the opportunity to begin annual screening between ages 40-44 based on personal preferences after discussing benefits and risks with their healthcare provider (qualified recommendation) 1
• This age group has a lower incidence of breast cancer (122.5 per 100,000 for ages 40-44 compared to 224.0 per 100,000 for ages 50-54) 2
• The benefit-to-harm ratio is less favorable in this age group, but screening can still detect early-stage disease 1

Women Ages 45-54

• Women should undergo annual mammography screening starting at age 45 (strong recommendation) 2
• Annual screening in this age group provides greater mortality reduction than biennial screening 1
• This recommendation is based on the higher incidence of breast cancer in this age group and more favorable benefit-to-harm ratio 1

Women Ages 55 and Older

• Women should transition to biennial screening or have the opportunity to continue annual screening based on personal preference 2
• Screening should continue as long as the woman is in good health with a life expectancy of at least 10 years 2
• There is no specific upper age limit for screening; decisions should be based on overall health status and life expectancy 1

Benefits of Mammography Screening

• Regular mammography screening is associated with a 15-20% reduction in breast cancer mortality 1
• Early detection allows for:
  • Less aggressive treatment options 1
  • Diagnosis at earlier stage 3
  • Better surgical options 3
  • More effective chemotherapy 3
• Annual screening results in more screening-detected tumors, tumors of smaller sizes, and fewer interval cancers than longer screening intervals 3

Potential Harms and Limitations

• False-positive results may lead to additional imaging, unnecessary biopsies, and temporary psychological distress 1
• Recall rates are approximately 10% of screening mammograms, with less than 2% resulting in recommendation for biopsy 4
• Overdiagnosis (detection of cancers that would not have become clinically evident during a woman's lifetime) is a potential harm 1
• Radiation exposure, though minimal with modern equipment 1

Clinical Breast Examination and Breast Self-Examination

• Clinical breast examination is not recommended for breast cancer screening among average-risk women at any age 2, 1
• Women should be aware of their breasts and promptly report any changes to their healthcare provider 1
• Formal instruction in breast self-examination has not been shown to reduce breast cancer mortality 1

Special Considerations for High-Risk Women

• Women with genetic mutations (BRCA1/BRCA2) or calculated lifetime risk ≥20% should receive annual MRI beginning at age 30, along with annual mammography 5
• Women with dense breast tissue should consider supplemental screening with MRI, as dense tissue increases cancer risk and decreases mammography sensitivity 5
• Women with personal histories of breast cancer diagnosed before age 50 should undergo annual MRI surveillance in addition to mammography 5
• Screening should begin 10 years younger than the youngest case in the family for those with family history 1

Mortality Reduction by Age Group

• Mortality reduction varies by age: 15% reduction for women aged 39-49 years, 14% for women aged 50-59 years, and 32% for women aged 60-69 years 1
• The number needed to screen to prevent one breast cancer death decreases with age: from 1770 for women 40-49 years to 835 for women 60-69 years (with 20% mortality reduction) 1

Practical Implementation

• Risk assessment should be performed for all women by age 25 to identify those at higher-than-average risk who may benefit from earlier screening 6
• Decisions about when to stop screening should be based on overall health and life expectancy rather than chronological age alone 2, 1
• For women at average risk, mammography remains the gold standard screening modality 7