Breast Cancer Screening (PDQ®): Screening - Health Professional Information [NCI]

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Note: Separate PDQ summaries on Breast Cancer Prevention; Breast Cancer Treatment; Male Breast Cancer Treatment; and Breast Cancer Treatment and Pregnancy are also available.

Screening by Mammography

Statement of benefit

Based on fair evidence, screening mammography in women aged 40 to 70 years decreases breast cancer mortality. The benefit is higher for older women, in part because their breast cancer risk is higher.

Description of the Evidence

  • Study Design: Meta-analysis of individual data from four randomized controlled trials (RCTs) [1] and three additional RCTs.[2,3,4]
  • Internal Validity: Validity of RCTs varies from poor to good. Internal validity of meta-analysis is good.
  • Consistency: Fair.
  • Magnitude of Effects on Health Outcomes: Relative breast cancer–specific mortality is decreased by 15% for follow-up analysis and 20% for evaluation analysis.[1] Absolute mortality benefit for women screened annually starting at age 40 years is 4 per 10,000 at 10.7 years.[5] The comparable number for women screened annually starting at age 50 years is approximately 5 per 1,000. Absolute benefit is approximately 1% overall but depends on inherent breast cancer risk, which rises with age.
  • External Validity: Good.

Statement of harms

Based on solid evidence, screening mammography may lead to the following harms:

Table 1. Harms of Screening Mammography

HarmStudy DesignInternal ValidityConsistencyMagnitude of EffectsExternal Validity
Treatment of insignificant cancers (overdiagnosis, true positives) can result in breast deformity, lymphedema, thromboembolic events, new cancers, or chemotherapy-induced toxicities.Descriptive population-based, autopsy series and series of mammary reduction specimens GoodGoodApproximately 33% of breast cancers detected by screening mammograms represent overdiagnosis.[6]Good
Additional testing (false-positives)Descriptive population-basedGoodGoodEstimated to occur in 50% of women screened annually for 10 years, 25% of whom will have biopsies.[7]Good
False sense of security, delay in cancer diagnosis (false-negatives) Descriptive population-based GoodGood6% to 46% of women with invasive cancer will have negative mammograms, especially if young, with dense breasts,[8,9] or with mucinous, lobular, or fast-growing cancers.[10]Good
Radiation-induced mutations can cause breast cancer, especially if exposed before age 30 years. Latency is more than 10 years, and the increased risk persists lifelong. Descriptive population-based GoodGoodBetween 9.9 and 32 breast cancers per 10,000 women exposed to a cumulative dose of 1 Sv. Risk is higher for younger women.[11,12]Good

Screening by Clinical Breast Examination

Statement of benefits

Based on fair evidence, screening by clinical breast examination reduces breast cancer mortality.

Description of the Evidence

  • Study Design: RCT, with inference.
  • Internal Validity: Good.
  • Consistency: Poor.
  • Magnitude of Effects on Health Outcomes: Breast cancer mortality was the same for women aged 50 to 59 years undergoing screening clinical breast examinations with or without mammograms.[4]
  • External Validity: Poor.

Statement of harms

Based on solid evidence, screening by clinical breast examination may lead to the following harms:

Table 2. Harms of Screening Clinical Breast Examination

HarmsStudy DesignInternal ValidityConsistencyMagnitude of EffectsExternal Validity
Additional testing (false-positives)Descriptive population-basedGoodGoodSpecificity in women aged 50 to 59 years ranged between 88% and 99%.[13,14]Good
False reassurance, delay in cancer diagnosis (false-negatives) Descriptive population-based GoodFairOf women with cancer, 17% to 43% had a negative clinical breast examination.[14]Poor

Screening by Breast Self-Examination

Statement of benefit

Based on fair evidence, teaching breast self-examination does not reduce breast cancer mortality.

Description of the Evidence

  • Study Design: One RCT, case-control trials, and cohort evidence.
  • Internal Validity: Good.
  • Consistency: Fair.
  • Magnitude of Effects on Health Outcomes: No difference in breast cancer mortality was seen after 10 years in Shanghai factory workers randomly assigned to receive breast self-examination instruction and reinforcement, compared with the control group. Forty percent of the women enrolled, however, were younger than 40 years.[15]
  • External Validity: Poor.

Statement of harms

Based on solid evidence, formal instruction and encouragement to perform breast self-examination leads to more breast biopsies and to the diagnosis of more benign breast lesions.

Description of the Evidence

  • Study Design: One RCT.
  • Internal Validity: Good.
  • Consistency: Fair.
  • Magnitude of Effects on Health Outcomes: Biopsy rate is 1.8% among the study population compared with 1.0% among the control group.[15]
  • External Validity: Poor.

References:

  1. Nyström L, Andersson I, Bjurstam N, et al.: Long-term effects of mammography screening: updated overview of the Swedish randomised trials. Lancet 359 (9310): 909-19, 2002.
  2. Shapiro S: Periodic screening for breast cancer: the Health Insurance Plan project and its sequelae, 1963-1986. Baltimore, Md: Johns Hopkins University Press, 1988.
  3. Miller AB, To T, Baines CJ, et al.: The Canadian National Breast Screening Study-1: breast cancer mortality after 11 to 16 years of follow-up. A randomized screening trial of mammography in women age 40 to 49 years. Ann Intern Med 137 (5 Part 1): 305-12, 2002.
  4. Miller AB, Baines CJ, To T, et al.: Canadian National Breast Screening Study: 2. Breast cancer detection and death rates among women aged 50 to 59 years. CMAJ 147 (10): 1477-88, 1992.
  5. Moss SM, Cuckle H, Evans A, et al.: Effect of mammographic screening from age 40 years on breast cancer mortality at 10 years' follow-up: a randomised controlled trial. Lancet 368 (9552): 2053-60, 2006.
  6. Zahl PH, Strand BH, Maehlen J: Incidence of breast cancer in Norway and Sweden during introduction of nationwide screening: prospective cohort study. BMJ 328 (7445): 921-4, 2004.
  7. Elmore JG, Barton MB, Moceri VM, et al.: Ten-year risk of false positive screening mammograms and clinical breast examinations. N Engl J Med 338 (16): 1089-96, 1998.
  8. Rosenberg RD, Hunt WC, Williamson MR, et al.: Effects of age, breast density, ethnicity, and estrogen replacement therapy on screening mammographic sensitivity and cancer stage at diagnosis: review of 183,134 screening mammograms in Albuquerque, New Mexico. Radiology 209 (2): 511-8, 1998.
  9. Kerlikowske K, Grady D, Barclay J, et al.: Likelihood ratios for modern screening mammography. Risk of breast cancer based on age and mammographic interpretation. JAMA 276 (1): 39-43, 1996.
  10. Porter PL, El-Bastawissi AY, Mandelson MT, et al.: Breast tumor characteristics as predictors of mammographic detection: comparison of interval- and screen-detected cancers. J Natl Cancer Inst 91 (23): 2020-8, 1999.
  11. Ronckers CM, Erdmann CA, Land CE: Radiation and breast cancer: a review of current evidence. Breast Cancer Res 7 (1): 21-32, 2005.
  12. Goss PE, Sierra S: Current perspectives on radiation-induced breast cancer. J Clin Oncol 16 (1): 338-47, 1998.
  13. Fenton JJ, Rolnick SJ, Harris EL, et al.: Specificity of clinical breast examination in community practice. J Gen Intern Med 22 (3): 332-7, 2007.
  14. Baines CJ, Miller AB, Bassett AA: Physical examination. Its role as a single screening modality in the Canadian National Breast Screening Study. Cancer 63 (9): 1816-22, 1989.
  15. Thomas DB, Gao DL, Ray RM, et al.: Randomized trial of breast self-examination in Shanghai: final results. J Natl Cancer Inst 94 (19): 1445-57, 2002.

Purpose of This Summary

This PDQ cancer information summary for health professionals provides comprehensive, peer-reviewed, evidence-based information about breast cancer screening. It is intended as a resource to inform and assist clinicians who care for cancer patients. It does not provide formal guidelines or recommendations for making health care decisions.

Reviewers and Updates

This summary is reviewed regularly and updated as necessary by the PDQ Screening and Prevention Editorial Board. Board members review recently published articles each month to determine whether an article should:

  • be discussed at a meeting,
  • be cited with text, or
  • replace or update an existing article that is already cited.

Changes to the summaries are made through a consensus process in which Board members evaluate the strength of the evidence in the published articles and determine how the article should be included in the summary.

Any comments or questions about the summary content should be submitted to Cancer.gov through the Web site's Contact Form. Do not contact the individual Board Members with questions or comments about the summaries. Board members will not respond to individual inquiries.

Levels of Evidence

Some of the reference citations in this summary are accompanied by a level-of-evidence designation. These designations are intended to help readers assess the strength of the evidence supporting the use of specific interventions or approaches. The PDQ Screening and Prevention Editorial Board uses a formal evidence ranking system in developing its level-of-evidence designations.

Permission to Use This Summary

PDQ is a registered trademark. Although the content of PDQ documents can be used freely as text, it cannot be identified as an NCI PDQ cancer information summary unless it is presented in its entirety and is regularly updated. However, an author would be permitted to write a sentence such as "NCI's PDQ cancer information summary about breast cancer prevention states the risks succinctly: [include excerpt from the summary]."

The preferred citation for this PDQ summary is:

National Cancer Institute: PDQ® Breast Cancer Screening. Bethesda, MD: National Cancer Institute. Date last modified <MM/DD/YYYY>. Available at: http://www.cancer.gov/cancertopics/pdq/screening/breast/healthprofessional. Accessed <MM/DD/YYYY>.

Images in this summary are used with permission of the author(s), artist, and/or publisher for use within the PDQ summaries only. Permission to use images outside the context of PDQ information must be obtained from the owner(s) and cannot be granted by the National Cancer Institute. Information about using the illustrations in this summary, along with many other cancer-related images, is available in Visuals Online, a collection of over 2,000 scientific images.

Disclaimer

The information in these summaries should not be used as a basis for insurance reimbursement determinations. More information on insurance coverage is available on Cancer.gov on the Coping with Cancer: Financial, Insurance, and Legal Information page page.

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More information about contacting us or receiving help with the Cancer.gov Web site can be found on our Contact Us for Help page. Questions can also be submitted to Cancer.gov through the Web site's Contact Form.

Last Revised: 2011-01-28

© 1995-2011 Healthwise, Incorporated. Healthwise, Healthwise for every health decision, and the Healthwise logo are trademarks of Healthwise, Incorporated. This information does not replace the advice of a doctor. Healthwise, Incorporated disclaims any warranty or liability for your use of this information. Your use of this information means that you agree to the Terms of Use. How this information was developed to help you make better health decisions.

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