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 decreases 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
  • Reduces advanced cancer (although no evidence regarding advanced cancer treatment)
    • USPSTF evidence review in women > 50 years of age: Relative risk 0.62 (95% CI, 0.46 – 0.83)
  • May increase life expectancy (ACS systematic review) but could not quantitate

HARMS OF MAMMOGRAPHY

False Positives (additional images and benign biopsies)

  • USPSTF review 10 yr cumulative false positive rate
    • Annual: 61% false positive / 7% require biopsy
    • Every 2 years: 42% false positive / 5% require biopsy
  • ACS review of the same data
    • 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

Discomfort

  • 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
    • USPSTF review suggests 10.7% – 22.7% based on RCT data
    • 1/8 cancers will be overdiagnosed and 2 to 3 women will be treated unnecessarily
  • Inclusion of Ductal Carcinoma in Situ may impact data
  • Other organizations such as ACS make the point that certain assumptions may not be verifiable in addition to bias in methodology and design

Radiation

  • USPSTF using modelling but not direct studies of radiation exposure estimates 2 per 100,000 deaths among women 50-59 yrs due to mammography screening
  • Other models in women 40-74 yrs suggest 125 cases of breast cancer and 25 cancer deaths due to radiation exposure, but 986 cancer deaths prevented

PROFESSIONAL GUIDELINES:

ACOG 2017

  • 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

USPSTF 2016

  • Start Age
    • Recommend at age 50
  • Screening Interval
    • > age 50: every 2 years until age 74
  • Stop Age
    • ≥ age 75:  Insufficient evidence to recommend for/against

ACS 2015

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

ACR 2010

  • Start Age
    • Recommend at age 40
  • Screening Interval
    • Annual
  • Stop Age
    • Stop when life expectancy is less than 5 to 7 years because of age/comorbid conditions

ACP 2019

  • Start Age
      • Offer at age 50
    • Age 40 – 49: 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

AAFP 2016

  • Start Age
    • Recommend at age 50
  • Screening Interval
    • Every 2 years
  • Stop Age
    • ≥ age 75:  Insufficient evidence to recommend for/against

NCCN 2019

  • Start Age
    • Recommend at age 40
  • 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 2018

  • Start Age
    • Recommend not to screen women age 40 to 49 (conditional recommendation; low-certainty evidence)
  • Screening Interval
    • Every 2 to 3 years
    • 50-69 years: “Conditional on the relative value that a woman places on possible benefits and harms from screening (conditional recommendation; very low-certainty evidence)
    • Age 50-59: 1333 women is the number needed to screen (NSS) to prevent one death from breast cancer (95% CI, 909 to 2857)
    • Age 60-69: NSS is 1087 (95% CI, 741 to 2325)
    • Age 70-74: NSS is 645 (95% CI, 441 to 1389)
  • Stop Age
    • No evidence found regarding harms vs benefits of screening ≥75 years

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 2019

  • 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 ages 25-39 and annually for ≥ age 40
    • USPSTF & AAFP: Insufficient evidence to recommend for or against
    • ACS, ACP & Canadian Task Force on Preventative Healthcare: Not recommended
  • 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 with imaging: recommendations from the Society of Breast Imaging and the ACR on the use of mammography, breast MRI, breast ultrasound, and other technologies for the detection of clinically occult breast cancer

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