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Mammography Guidelines for Average-Risk Women


Professional organizations continue to release evidence based guidance on mammography, with ACP the latest to provide updated recommendations. While required frequency and starting age may differ, they all emphasize shared decision making with patients, which entails counseling about uncertainty, risk/benefit and related patient values.


  • Appears to decrease breast cancer mortality by 15 to 20%
    • Studies demonstrate varying magnitude
    • ACS (RCT data): Relative risk 0.80 to 0.82
    • Recent data from the Canadian National Breast Screening Study did not show decrease when comparing mammography to controls, perhaps due to more recent improvements in treatments but does not take into account advances in imaging
  • May increase life expectancy (ACS systematic review) but could not quantitate


False Positives (additional images and benign biopsies)

  • USPSTF review
    • Collaborative modeling data: Screening biennially from ages 40 to 74 years would result in 1376 false-positive results per 1000 women screened over a lifetime of screening
  • ACS review of the same data
    • Increased risk of false positive with dense breasts among women 40 to 49
    • Callbacks minimized if prior films available

Anxiety and Distress

  • May persist even if follow-up is normal
  • Financial concerns as patient may be responsible for paying for additional tests


  • USPSTF review identified mammography as being a painful procedure
  • Follow-up procedures may also result in pain

Overdiagnosis and Overtreatment

  • Overdiagnosis is defined as detecting a cancer that would have remained indolent and not become apparent without screening
  • Overtreatment is defined as treatment for an overdiagnosed cancer
  • Difficult to discern actual number of overdiagnosed cancers
    ◦ Collaborative modeling data (USPSTF): Screening biennially from ages 40 to 74 years would lead to 14 overdiagnosed cases of breast cancer per 1000 persons screened over the lifetime of screening with a very wide range of estimates (4 to 37 cases) across model
  • Other organizations such as ACS make the point that certain assumptions may not be verifiable in addition to bias in methodology and design

Diversity, Equity Inclusion Considerations 

  • USPSTF cites that Black women are 40% more likely to die from breast cancer than Caucasian women with more aggressive cancers at younger ages 
  • Urgently calling for more research to see if different screening methods are needed for Black women 
  • ACR updated guidelines to include transgender patients stating “Annual screening at age 40 is recommended for transfeminine (male-to-female) patients who have used hormones for ≥5 years, as well as for transmasculine (female-to-male) patients who have not had mastectomy”



  • Start Age
    • Recommend at age 50
    • Offer from age 40 (shared decision making)
  • Screening Interval
    • Every 1 or 2 years (shared decision making)
  • Stop Age
    • Age 75
    • > 75 shared decision making including overall health and longevity


  • Start Age
    • Recommend at 40 years
  • Screening Interval: Every 2 years until 74 years
  • Stop Age
    • ≥ 75 years:  Insufficient evidence to recommend for/against


  • Start Age
    • Recommend at age 45 years | Consider 40 years if patient desires
  • Screening Interval
    • 45 to 50 years: annual
    • ≥55 years: Every 2 years or can choose annual
  • Stop Age
    • Continue if good health and life expectancy >10 years


  • Start Age
    • Recommend at 40 years
  • Screening Interval: Annual
  • Stop Age
    • “Screening should continue past age 74 without an upper age limit, unless severe comorbidities limit life expectancy or ability to accept treatment.”


  • Start Age
    • Recommended at 50 years
    • 40 to 49 years: Discuss risks vs benefits and patient preference (“potential harms outweigh the benefits for most women” in this age bracket )
  • Screening Interval: Every 2 years
  • Stop Age
    • Screening not recommended for women ≥75
    • Life expectancy ≤10 years


  • Start Age
    • Recommend at 40 years
  • Screening Interval: Annual
  • Stop Age
    • Upper age limit not yet established
  • Consider comorbidities that may impact life expectancy (≤10 years)

Canadian Task Force on Preventative Healthcare

  • Start Age
    • Recommend not to screen women 40 to 49 years (conditional recommendation; low-certainty evidence)
  • Screening Interval
  • Every 2 to 3 years
  • 50 to 69 years: “Conditional on the relative value that a woman places on possible benefits and harms from screening (conditional recommendation; very low-certainty evidence)”
  • 50 to 59 years: 1333 women is the number needed to screen (NNS) to prevent one death from breast cancer (95% CI, 909 to 2857)
  • 60-69 years: NNS is 1087 (95% CI, 741 to 2325)
  • 70-74 years: NNS is 645 (95% CI, 441 to 1389)

Note: The Canadian Task Force did not make any significant change from the previous guideline, however certainty of evidence – now ‘very low- to low-certainty’ was downgraded based on serious concerns of previous study bias

American Society of Breast Surgeons

  • Start Age
    • Non-dense breasts (A and B density): 3D preferred modality | Age 40 | No need for supplemental imaging
    • Dense breasts (C and D density): 3D preferred modality | Age 40 | Consider supplemental imaging
  • Screening Interval
    • Annual
  • Stop Age
    • When life expectancy is <10 years


  • Clinical Breast Examination (CBE)
    • ACOG & NCCN: Offer every 1 to 3 years for women 25 to 39 years and annually for ≥ 40 years
    • USPSTF & AAFP: Insufficient evidence to recommend for or against
    • ACS, ACP & Canadian Task Force on Preventative Healthcare: Not recommended
    • WHO: CBE may be of benefit for women age 50 to 69 years with poor access to healthcare resources 
  • Most professional organizations find insufficient evidence to recommend adjunctive screening using breast ultrasonography, MRI, Digital Breast Tomosynthesis, or other method in the setting of a normal mammogram and no other risk factors

Learn More – Primary Sources:

ACOG Practice Bulletin 179: Breast Cancer Risk Assessment and Screening in Average-Risk Women

Screening for breast cancer: U.S. Preventive Services Task Force recommendation statement

Twenty five year follow-up for breast cancer incidence and mortality of the Canadian National Breast Screening Study: randomised screening trial

Canadian Task Force: Recommendations on screening for breast cancer in women aged 40–74 years who are not at increased risk for breast cancer

Breast Cancer Screening Recommendations Inclusive of All Women at Average Risk: Update from the ACR and Society of Breast Imaging

Breast Cancer Screening for Women at Average Risk: 2015 Guideline Update From the American Cancer Society

Screening for Breast Cancer in Average-Risk Women: A Guidance Statement From the American College of Physicians

AAFP: Summary of Recommendations for Clinical Preventative Services

NCCN Guidelines: Breast Cancer Screening and Diagnosis

ASBrS: Position Statement on Screening Mammography

Radiation-Induced Breast Cancer Incidence and Mortality from Digital Mammography Screening: A Modeling Study 

WHO position paper on mammography screening 

American Cancer Society Recommendations for the Early Detection of Breast Cancer

BI-RADS: Standardizing Breast Imaging and Reporting


BI-RADS: Breast Imaging Reporting and Data System, was developed by the American College of Radiology (ACR) to standardize mammogram reporting, as well as breast ultrasound and MRI reporting.

The standard mammogram report includes the following

  • Indication and type of mammogram (screening/diagnostic)
  • Statement regarding breast density
  • Description of pertinent findings including size and location, oriented by quadrant and clock position
  • Summary of important findings and BI-RADS category


BI-RADS Classification Standardizes Findings and Recommendations for Further Management

BI-RADS 0 : Incomplete

  • Recall for additional imaging/comparison with prior examinations, or both

BI-RADS 1: Negative  (Essentially 0% chance of malignancy)

  • Routine screening

BI-RADS 2: Benign (Essentially 0% likelihood of malignancy)

  • Routine screening

BI-RADS 3: Probably benign (> 0% but ≤ 2% likelihood of malignancy)

  • 6 month follow-up or continued surveillance

BI-RADS 4: Suspicious (> 2% but < 95% likelihood of malignancy)

  • 4A: Low suspicion for malignancy (> 2% to ≤ 10% likelihood)
  • 4B: Moderate suspicion for malignancy (> 10% to ≤ 50% likelihood)
  • 4C: High suspicion for malignancy (> 50% to < 95% likelihood)
  • Tissue diagnosis needed for all BI-RADS 4  categories

BI-RADS 5: Highly suggestive of malignancy (95% likelihood of malignancy)

  • Tissue diagnosis needed

BI-RADS 6: Known, biopsy proven malignancy

  • Surgical excision when appropriate

Density Categories

  • Category a: Breasts are almost entirely fatty
    • Prevalence: 10% of the population
    • Mammography considered highly sensitive in this setting (88%)
  • Category b: There are scattered areas of fibroglandular density
    • Prevalence: 43% of the population
    • Still sensitive but decreased from category a (82%)
  • Category c: Breasts are heterogeneously dense
  • Category d: Breasts are extremely dense
    • Significantly lowers sensitivity of mammography (62%)
    • Note: Breast cancer risk is 2.1 relative risk compared to average breast density

Learn More – Primary Sources:

ACOG Practice Bulletin No 164. Diagnosis and Management of Benign Breast Disorders 

ACR BI-RADS® Atlas, Breast Imaging Reporting and Data System

ACOG Committee Opinion 625: Management of with Dense Breasts Diagnosed with Mammography