viernes, 27 de diciembre de 2019

Breast Cancer Screening (PDQ®)–Health Professional Version - National Cancer Institute

Breast Cancer Screening (PDQ®)–Health Professional Version - National Cancer Institute

National Cancer Institute

Breast Cancer Screening (PDQ®)–Health Professional Version

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Overview

Note: Separate PDQ summaries on Breast Cancer Prevention, Breast Cancer Treatment (Adult), Male Breast Cancer Treatment, and Breast Cancer Treatment During Pregnancy are also available.
Mammography is the most widely used screening modality for the detection of breast cancer. There is evidence that it decreases breast cancer mortality in women aged 50 to 69 years and that it is associated with harms, including the detection of clinically insignificant cancers that pose no threat to life (overdiagnosis). The benefit of mammography for women aged 40 to 49 years is uncertain.[1,2] There are randomized trials in India, Iran, and Egypt that have studied the use of clinical breast examination (CBE) as a screening test. Some of these studies have suggested a shift in late-stage disease; however, there is still insufficient evidence to conclude a mortality benefit.[3-8] Breast self-exam has been shown to have no mortality benefit. No results have been published on the outcomes of incidence or mortality for CBE.
Technologies such as ultrasound, magnetic resonance imaging, and molecular breast imaging are being evaluated, usually as adjuncts to mammography, and are not primary screening tools in the average population.
Informed medical decision making is increasingly recommended for individuals who are considering cancer screening. Many different types and formats of decision aids have been studied. (Refer to the PDQ summary on Cancer Screening Overview for more information.)

Screening With Mammography

Benefits

Randomized controlled trials (RCTs) initiated 50 years ago provide evidence that screening mammography reduces breast cancer–specific mortality for women aged 60 to 69 years (solid evidence) and women aged 50 to 59 years (fair evidence). Population-based studies done more recently raise questions as to the benefits to screened populations who participate in screening for longer time periods.
Magnitude of Effect: Based on a meta-analysis of RCTs, the number of women needed to invite for screening to prevent one breast cancer death depends on the woman’s age: for women aged 39 to 49 years, 1,904 women needed (95% confidence interval [CI], 929–6,378); for women aged 50 to 59 years, 1,339 women needed (95% CI, 322–7,455); and for women aged 60 to 69 years, 377 women needed (95% CI, 230–1,050).[9]
  • Study Design: RCTs, population-based evidence.
  • Internal Validity: Variable, but meta-analysis of RCTs is good.
  • Consistency: Poor.
  • External Validity: Uncertain.
The validity of meta-analyses of RCT demonstrating a mortality benefit is limited by improvements in medical imaging and treatment in the decades since their completion. The 25-year follow-up from the Canadian National Breast Screening Study (CNBSS),[10] completed in 2014, showed no mortality benefit associated with screening mammograms.

Harms

Based on solid evidence, screening mammography may lead to the following harms:
  • Overdiagnosis and Resulting Treatment of Insignificant Cancers: Some screen-detected cancers are life threatening and others are not, with no definitive way of discriminating between them. Therefore, standard cancer therapies, including surgery, radiation, endocrine therapy, chemotherapy, and therapies targeting the HER2 receptor, are recommended for all cases, even for patients who will gain no benefit.
    • Magnitude of Effect: Between 20% and 50% of screen-detected cancers represent overdiagnosis based on patient age, life expectancy, and tumor type (ductal carcinoma in situ and/or invasive).[11,12] These estimates are based on two imperfect analytic methods:[11,13]
      1. Long-term follow-up of RCTs of screening.
      2. The calculation of excess incidence in large screening programs.[11,12]
    • Study Design: RCTs, descriptive, population-based comparisons, autopsy series, and series of mammary reduction specimens.
  • False Positives with Additional Testing and Anxiety.
    • Magnitude of Effect: In the United States, approximately 10% of women are recalled for further testing after a screening examination, however, only 0.5% of tested women have cancer; thus, approximately 9.5% of tested women will have a false-positive exam.[14,15] Approximately 50% of women screened annually for 10 years in the United States will experience a false positive; of these, 7% to 17% will undergo biopsies.[16,17] Additional testing is less likely when prior mammograms are available for comparison.
    • Study Design: Descriptive, population based.
  • False Negatives with False Sense of Security and Potential Delay in Cancer Diagnosis.
    • Magnitude of Effect: Invasive breast cancer will be present but undetected by mammography (false negative) in 6% to 46% of exams. False-negative exams are more likely for mucinous and lobular types of cancer, for rapidly growing interval tumors which become detectable between regular mammograms and in dense breasts, which are common in younger women.[18-20]
    • Study design: Descriptive, population-based.
  • Radiation-Induced Breast Cancer: Radiation-induced mutations occur with radiation doses higher than those used in a single mammography examination, so the exposure associated with a typical two-view mammogram is extremely unlikely to cause cancer.[21,22]
    • Magnitude of Effect: Theoretically, annual mammograms in women aged 40 to 80 years may cause up to one breast cancer per 1,000 women.[21,22]
    • Study design: Descriptive, population-based.
For all of these conclusions regarding potential harms from screening mammography, internal validity, consistency, and external validity are good.

Clinical Breast Examination (CBE)

Benefits

The CNBSS trial did not study the efficacy of CBE versus no screening. Ongoing randomized trials, two in India and one in Egypt, are designed to assess the efficacy of screening CBE but have not reported mortality data.[3-8] Thus, the efficacy of screening CBE cannot be assessed yet.
  • Magnitude of Effect: The current evidence is insufficient to assess the additional benefits and harms of CBE. The single RCT comparing high-quality CBE with screening mammography showed equivalent benefit. CBE accuracy in the community setting might be lower than in the RCT.[3-6]
  • Study Design: Single RCT, population cohort studies.
  • Internal Validity: Good.
  • Consistency and External Validity: Poor.

Harms

Screening by CBE may lead to the following harms:
  • False Positives with Additional Testing and Anxiety.
    • Magnitude of effect: Specificity in women aged 50 to 59 years was 88% to 99%, yielding a false-positive rate of 1% to 12% for all women screened.[23]
    • Study Design: Descriptive, population based.
    • Internal Validity, Consistency, and External Validity: Good.
  • False Negatives with Potential False Reassurance and Delay in Cancer Diagnosis.
    • Magnitude of Effect: Of women with cancer, 17% to 43% have a negative CBE. Sensitivity is higher with longer duration and higher quality of the examination by trained personnel.
    • Study Design: Descriptive, population based.
    • Internal and External Validity: Good.
    • Consistency: Fair.

Breast Self-Examination (BSE)

Benefits

BSE has been compared with no screening and has been shown to have no benefit in reducing breast cancer mortality.
  • Magnitude of Effect: No effect.[24,25]
  • Study Design: Two RCTs.
  • Internal Validity and Consistency: Fair.
  • External Validity: Poor.

Harms

There is solid evidence that formal instruction and encouragement to perform BSE leads to more breast biopsies and more diagnoses of benign breast lesions.
  • Magnitude of Effects on Health Outcomes: Biopsy rate was 1.8% among the study population compared with 1.0% among the control group.[24]
  • Study Design: Two RCTs, cohort studies.
  • Internal Validity: Good.
  • Consistency: Fair.
  • External Validity: Poor.
References
  1. 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. [PUBMED Abstract]
  2. Moss SM, Wale C, Smith R, et al.: Effect of mammographic screening from age 40 years on breast cancer mortality in the UK Age trial at 17 years' follow-up: a randomised controlled trial. Lancet Oncol 16 (9): 1123-32, 2015. [PUBMED Abstract]
  3. Hassan LM, Mahmoud N, Miller AB, et al.: Evaluation of effect of self-examination and physical examination on breast cancer. Breast 24 (4): 487-90, 2015. [PUBMED Abstract]
  4. Anderson BO, Bevers TB, Carlson RW: Clinical Breast Examination and Breast Cancer Screening Guideline. JAMA 315 (13): 1403-4, 2016. [PUBMED Abstract]
  5. Yen AM, Tsau HS, Fann JC, et al.: Population-Based Breast Cancer Screening With Risk-Based and Universal Mammography Screening Compared With Clinical Breast Examination: A Propensity Score Analysis of 1 429 890 Taiwanese Women. JAMA Oncol 2 (7): 915-21, 2016. [PUBMED Abstract]
  6. Myers ER, Moorman P, Gierisch JM, et al.: Benefits and Harms of Breast Cancer Screening: A Systematic Review. JAMA 314 (15): 1615-34, 2015. [PUBMED Abstract]
  7. Mittra I, Mishra GA, Singh S, et al.: A cluster randomized, controlled trial of breast and cervix cancer screening in Mumbai, India: methodology and interim results after three rounds of screening. Int J Cancer 126 (4): 976-84, 2010. [PUBMED Abstract]
  8. Sankaranarayanan R, Ramadas K, Thara S, et al.: Clinical breast examination: preliminary results from a cluster randomized controlled trial in India. J Natl Cancer Inst 103 (19): 1476-80, 2011. [PUBMED Abstract]
  9. Nelson HD, Tyne K, Naik A, et al.: Screening for breast cancer: an update for the U.S. Preventive Services Task Force. Ann Intern Med 151 (10): 727-37, W237-42, 2009. [PUBMED Abstract]
  10. Miller AB, Wall C, Baines CJ, et al.: Twenty five year follow-up for breast cancer incidence and mortality of the Canadian National Breast Screening Study: randomised screening trial. BMJ 348: g366, 2014. [PUBMED Abstract]
  11. Welch HG, Black WC: Overdiagnosis in cancer. J Natl Cancer Inst 102 (9): 605-13, 2010. [PUBMED Abstract]
  12. Bleyer A, Welch HG: Effect of three decades of screening mammography on breast-cancer incidence. N Engl J Med 367 (21): 1998-2005, 2012. [PUBMED Abstract]
  13. Yen MF, Tabár L, Vitak B, et al.: Quantifying the potential problem of overdiagnosis of ductal carcinoma in situ in breast cancer screening. Eur J Cancer 39 (12): 1746-54, 2003. [PUBMED Abstract]
  14. Jørgensen KJ, Gøtzsche PC: Overdiagnosis in publicly organised mammography screening programmes: systematic review of incidence trends. BMJ 339: b2587, 2009. [PUBMED Abstract]
  15. Rosenberg RD, Yankaskas BC, Abraham LA, et al.: Performance benchmarks for screening mammography. Radiology 241 (1): 55-66, 2006. [PUBMED Abstract]
  16. 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. [PUBMED Abstract]
  17. Hubbard RA, Kerlikowske K, Flowers CI, et al.: Cumulative probability of false-positive recall or biopsy recommendation after 10 years of screening mammography: a cohort study. Ann Intern Med 155 (8): 481-92, 2011. [PUBMED Abstract]
  18. 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. [PUBMED Abstract]
  19. 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. [PUBMED Abstract]
  20. 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. [PUBMED Abstract]
  21. Ronckers CM, Erdmann CA, Land CE: Radiation and breast cancer: a review of current evidence. Breast Cancer Res 7 (1): 21-32, 2005. [PUBMED Abstract]
  22. Goss PE, Sierra S: Current perspectives on radiation-induced breast cancer. J Clin Oncol 16 (1): 338-47, 1998. [PUBMED Abstract]
  23. 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. [PUBMED Abstract]
  24. 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. [PUBMED Abstract]
  25. Semiglazov VF, Manikhas AG, Moiseenko VM, et al.: [Results of a prospective randomized investigation [Russia (St.Petersburg)/WHO] to evaluate the significance of self-examination for the early detection of breast cancer]. Vopr Onkol 49 (4): 434-41, 2003. [PUBMED Abstract]
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