SUMMARY:

ACOG has released new guidance on mammography that is based on evidence as well as an emphasis on shared decision making with patients, which entails counseling about uncertainty, risk/benefit and related patient values. Multiple other professional organizations have also released guidelines and these too are summarized below.

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

SUMMARY OF 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
  • Age 40: Patient may choose every 1 or 2 years (weigh harms/benefits)
• 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
  • Age 40 – 44: Patient may choose annual
• 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 2015

• Start Age
  • Encourage from age 50
  • Age 40 – 49: If requested by patient in otherwise good health (following discussion of harms/benefit)
• Screening Interval
  • Every 2 years
• Stop Age
  • Screening at age ≥ 75 is not recommended

AAFP 2016

• Start Age
  • Recommend at age 50
  • Age 40 – 49: Individualized decision making (for women who place higher value on potential benefit compared to harms)
• Screening Interval
  • Every 2 years
• Stop Age
  • ≥ age 75:  Insufficient evidence to recommend for/against

NCCN 2018

• Start Age
  • Recommend at age 40
• Screening Interval
  • Annual
• Stop Age
  • Upper age limit not yet established
  • If comorbidities would prohibit intervention, do not screen regardless of age

Canadian Task Force on Preventative Healthcare 2018

• Start Age
  • Recommend not to screen women age 40 to 49 (conditional recommendation; low-certainty evidence)
  • Age 50 – conditional recommendations (see below)
• 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

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, ACP & AAFP: Insufficient evidence to recommend for or against
  • ACS & 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 Cancer: Advice for High-Value Care from the American College of Physicians

AAFP: Summary of Recommendations for Clinical Preventative Services

NCCN Guidelines: Breast Cancer Screening and Diagnosis Version

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