BI-RADS: Standardizing Breast Imaging and Reporting 

WHAT IS IT?

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

KEY POINTS:

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
  • Prevalence: 39%
  • Small masses may be obscured
  • Sensitivity drops to 69%
  • Note: Breast cancer risk is 1.2 relative risk compared to average breast density
• Category d: Breasts are extremely dense
  • 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

Mammography Guidelines for Average-Risk Women

SUMMARY:

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.

BENEFITS OF MAMMOGRAPHY

• Appears to decrease breast cancer mortality by 15 to 20%
  • Studies demonstrate varying magnitude
  • ACS (RCT data): Relative risk 0.80-0.82
  • 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 in to account advances in imaging
• May increase life expectancy (ACS systematic review) but could not quantitate

HARMS OF MAMMOGRAPHY

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
  • Increased risk of false positive with dense breasts among women 40-49
  • 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

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 models
• Other organizations such as ACS make the point that certain assumptions may not be verifiable in addition to bias in methodology and design

PROFESSIONAL GUIDELINES:

ACOG

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

USPSTF

• Start Age
  • Recommend at 40 years

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

ACS

• Start Age
  • Recommend at age 45 years | Consider 40 years if patient desires

• Screening Interval
  • 45 – 50 years: annual
  • ≥55 years: Every 2 years or can choose annual
• Stop Age
  • Continue if good health and life expectancy >10 years

ACR

• 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.“

Note: 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” 

ACP

• Start Age
  • Recommended at 50 years
  • 40-49 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

NCCN

• 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)

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

ADDITIONAL KEY POINTS: 

• 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

ACOG Practice Update: Age to Initiate Routine Breast Cancer Screening

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

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

ACS: Recommendations for the Early Detection of Breast Cancer Screening for Women at Average Risk

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

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