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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 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 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 to 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 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

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% to 22.7% based on RCT data
    • 1/8 cancers will be overdiagnosed
  • 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 to 59 yrs due to mammography screening
  • Other models in women 40 to 74 yrs suggest 125 cases of breast cancer and 25 cancer deaths due to radiation exposure, but 986 cancer deaths prevented

PROFESSIONAL GUIDELINES:

ACOG

  • 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

  • Start Age
    • Recommend at 50 years | Consider 40 years if patient desires
  • 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 to 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 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

AAFP

  • Start Age
  • Recommend at 50 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)

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

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

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