Putting Prevention into Practice: An Evidence-Based Approach

Screening for Breast Cancer



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Am Fam Physician. 2002 Dec 15;66(12):2283-2284.

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Case Study

GK is a 46-year-old woman who presents to your office for a well-woman examination. She informs you that her 51-year-old friend was diagnosed with breast cancer one month ago and that she is worried about getting breast cancer. On further inquiry, you learn that she delivered her only child when she was 32 years of age and has no family history for breast cancer. She does not perform breast self-examinations and has never had a mammogram. GK asks for your advice on breast cancer screening.

Case Study Questions

1. According to recommendations from the U.S. Preventive Services Task Force (USPSTF), which one of the following options is best for this patient?

  • A. Discuss the harms and benefits of screening, and offer screening because she is older than age 40.

  • B. Do not offer screening because she is younger than age 50.

  • C. Offer screening to obtain a baseline examination, and begin routine screening at age 50.

  • D. Discuss the harms and benefits of screening, and offer screening because she is older than age 40; continue screening every one to two years until age 70. E. Screening is not indicated because she is at low risk for developing breast cancer.

2. According to recommendations from the USPSTF, which one of the following strategies is best to screen for breast cancer?

  • A. Monthly breast self-examinations combined with an annual clinical breast examination.

  • B. Monthly breast self-examinations and mammography every one to two years.

  • C. Clinical breast examination every one to two years.

  • D. Mammography with or without clinical breast examination every one to two years.

  • E. Routine breast self-examinations and mammography with or without clinical breast examinations every one to two years.

3. Which of the following statements regarding the benefits and harms of screening for breast cancer is/are correct?

  • A. The majority (80 to 90 percent) of patients with abnormal screening mammograms are diagnosed with breast cancer.

  • B. In general, the benefits of screening for breast cancer increase as a woman becomes older.

  • C. In general, the harms of screening for breast cancer increase as a woman becomes older.

  • D. The balance of benefits and harms and the decision about when to initiate screening vary from patient to patient.

Answers

1. The correct answer is A. The USPSTF concluded that mammography screening every one to two years significantly reduces mortality from breast cancer and recommends screening for breast cancer in women age 40 and older. However, the precise age at which the potential benefits of mammography justify the possible harms is a subjective choice. Women at higher risk for breast cancer (e.g., those with a family history of breast cancer in a mother or sister, first childbirth after age 30, or previous biopsy revealing atypical hyperplasia1) are more likely to benefit from screening. Most, but not all, studies indicate a mortality benefit for women undergoing mammography at 40 to 49 years of age2, but determining the incremental benefit of beginning screening at age 40 rather than at age 50 is difficult. Evidence that breast cancer screening significantly reduces mortality from breast cancer is strongest for women 50 to 69 years of age, and the USPSTF concluded that the evidence is generalizable to women age 70 and older if their life expectancy is not compromised by comorbid conditions.

2. The correct answer is D. The USPSTF recommends screening for breast cancer with mammography, with or without clinical breast examination, every one to two years for women age 40 and older. Based on the available data, the USPSTF could not determine the benefits of screening with clinical breast examination alone or the incremental benefit of adding the examination to mammography. The USPSTF found insufficient evidence to recommend for or against the teaching or performing of routine breast self-examination.

3. The correct answers are B and D. Because the prevalence of breast cancer increases as women age, the absolute probability of a benefit from regular mammography also increases.3 Similarly, the likelihood of harms (resulting from false-positive findings) decreases as women age. Similar to other cancer screening tests, the vast majority (80 to 90 percent) of abnormal screening mammograms or clinical breast examinations are false-positives.4 These may necessitate follow-up testing or invasive procedures such as breast biopsy and can result in anxiety, inconvenience, and discomfort. Radiation-induced breast cancer is a potential concern, but there are limited data to assess this risk. The balance of benefits and potential harms grows more favorable along a continuum with age, yet varies individually based on risk factors and personal beliefs.

REFERENCES

1. Miller BA, Kolonel LN, Bernstein L, Young JL Jr, Swanson GM, West D, et al, eds. Racial/ethnic patterns of cancer in the United States 1988–1992. Accessed November, 2002, at: www.cancer.gov/cancerinformation/doc.aspx?viewid=A738FB 64-96F6-483E-AD40-6D61D06ED2E9.

2. Humphrey LL, Helfand M, Chan BK. Breast cancer screening: a summary of the evidence for the U.S. Preventive Services Task Force. Ann Intern Med. 2002;137:347–60.

3. American Cancer Society. Breast cancer facts and figures, 2001–2002. Accessed November, 2002, at www.cancer.org/docroot/STT/content/STT_1x_Breast_Cancer_Facts_and_Figures_2001-2002.asp.

4. Humphrey LL, Chan BK, Detlefsen S, Helfand M. Screening for breast cancer. Systematic evidence review no. 15 (Prepared by the Oregon Health & Science University Evidence-based Practice Center under contract no. 290-97-0018). Accessed November, 2002, at: www.ahrq.gov/clinic/serfiles.htm.

The case study and answers to the following questions on screening for breast cancer are based on the recommendations of the current U.S. Preventive Services Task Force (USPSTF), part of the Put Prevention Into Practice program of the Agency for Healthcare Research and Quality (AHRQ). This recommendation was released in 2002 and is an update of the 1996 recommendation on screening for breast cancer. More detailed information on this subject is available in the Systematic Evidence Review, Summary of the Evidence, and USPSTF Recommendations and Rationale on the AHRQ Web site (www.uspreventiveservicestaskforce.org) and through the National Guideline Clearinghouse ( www.guideline.gov)

This case study is part of AFP's CME. See “Clinical Quiz” on page 2203



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