Biennial Mammography: Definition and Recommendations
Biennial mammography refers to breast cancer screening with mammography performed every two years, which provides the best overall balance of benefits and harms for most women aged 50-74 years. 1
Definition and Purpose
- Biennial mammography is a breast cancer screening approach where mammography is performed every 2 years rather than annually or at longer intervals 1
- It is primarily recommended for average-risk women aged 50-74 years as the standard screening interval 1
- Digital mammography has essentially replaced film mammography as the primary method for breast cancer screening in the United States 1
Benefits of Biennial Screening
- For women at average risk for breast cancer, most of the benefit of mammography results from biennial screening during ages 50 to 74 years 1
- Women aged 60-69 years are most likely to avoid breast cancer death through mammography screening 1
- Biennial screening provides a mortality reduction benefit while minimizing potential harms 2
- Studies indicate relative risk reduction for breast cancer mortality of 0.86 for women aged 50-59 years and 0.67 for those aged 60-69 years with screening 2
Balance of Benefits and Harms
- Biennial screening reduces the cumulative false-positive rates compared to annual screening (42% vs 61% over 10 years) 3
- Biennial screening reduces unnecessary biopsy recommendations (5% vs 7% over 10 years) compared to annual screening 3
- Overdiagnosis rates are lower with less frequent screening, with rates from randomized trials estimated at 11% to 22% 3
- The U.S. Preventive Services Task Force determined that biennial screening provides the best overall balance of benefits and harms for most women 1
Age-Specific Recommendations
- For women aged 50-74 years: Biennial screening mammography is strongly recommended (Grade B recommendation) 1
- For women aged 40-49 years: The decision to start biennial screening should be individualized based on the woman's values regarding potential benefits and harms 1
- For women aged ≥75 years: Evidence is insufficient to assess the balance of benefits and harms 1
Special Considerations
- Hispanic women aged 50-74 years may have an increased risk of late-stage disease and larger tumors with biennial versus annual screening 4
- Asian women aged 40-49 years may have an elevated risk of positive lymph nodes with biennial versus annual screening 4
- Women with a parent, sibling, or child with breast cancer are at higher risk and may benefit more from beginning screening in their 40s 1
- These recommendations apply to asymptomatic women who do not have preexisting breast cancer, high-risk breast lesions, or genetic mutations like BRCA1/BRCA2 1
International Perspectives
- The World Health Organization suggests a screening interval of two years for women aged 50-69 years in well-resourced settings 1
- The American College of Physicians recommends screening with mammography every 2 to 3 years for women aged 50 to 74 years 1
- European guidelines also generally support biennial screening for women aged 50-69 years 5, 6
Common Pitfalls
- Assuming that more frequent screening always provides better outcomes - studies show biennial screening maintains most benefits while reducing harms 6
- Applying the same screening interval to all women regardless of age and risk factors - recommendations should be adjusted based on individual risk profiles 1
- Overlooking the cumulative risk of false positives with more frequent screening, which can lead to unnecessary anxiety, additional testing, and biopsies 3