Putting Prevention into Practice: An Evidence-Based Approach
Screening for Skin Cancer
Am Fam Physician. 2002 Apr 1;65(7):1401-1402.
A 65-year-old white man is in your office for a routine evaluation of his blood pressure. He complains of decreased urinary stream and nocturia. You notice that he has not had a rectal examination in the past two years, and you prepare to do this examination. When he has disrobed, you notice an irregularly shaped, dark skin lesion on the upper right posterior leg. He is unaware of the lesion.
1. Which one of the following statements regarding risk factors for melanoma is true?
A. The individual can modify most known risk factors for melanoma.
B. Melanoma predominantly strikes those between the ages of 20 and 50 years.
C. The presence of atypical moles is a strong risk factor.
D. Women are disproportionately affected by melanoma.
E. None of the above statements is true.
2. Which of the following statements is/are true about periodic Total Body Skin Examination as a screening test for skin cancer? (Mark all that apply.)
A. Melanomas detected by screening are thinner, on average, than melanomas discovered in the course of routine care.
B. Periodic screening has been shown to reduce melanoma mortality.
C. Most cancers detected by screening are basal cell and squamous cell cancers that are much less likely to be fatal.
D. Primary care physicians are much less likely than dermatologists to recognize skin lesions with features suggestive of melanoma.
1. The answer is C: the most well-established risk groups for malignant melanoma include advancing age, fair skin, atypical moles, and more than 50 moles (>2 mm). None of these risk factors is modifiable by the patient. Other risk factors for melanoma are red or light hair, very heavy sun exposure, and family history of melanoma. It is important for clinicians to be aware of these high-risk categorizations; one study found that most high-risk patients were not aware of their status.1 The benefits of screening with total body examination, even in high-risk groups, have not been established. The use of questionnaires or inter views to assess risk factors and prompt selective referral for total-body skin examination is likely the most promising strategy for melanoma screening, but the USPSTF finds insufficient evidence to recommend for or against this at present.
The majority of cases of melanoma occur in middle age and later, especially among men. Men over age 50 comprise 50 percent of all deaths from malignant melanoma. Men over age 65 comprise 5.2 percent of the U.S. population and 22 percent of new cases of malignant melanoma, while women aged 65 and older comprise 7.4 percent of the population and 14 percent of the new cases. Since most elderly individuals consult a clinician at least annually, case-finding by clinicians focusing on the elderly may be the most effective strategy to address the excessive burden of disease in older adults. Clinicians should remain alert for skin lesions with malignant features noted in the context of physical examinations performed for other reasons.
2. The answers are A and C: the USPSTF has concluded that the evidence is insufficient to recommend for or against total-body skin examination because no randomized or case-controlled trials have been conducted to ascertain whether screening reduces mortality or increases quality of life. The majority of skin cancers are basal cell and squamous cell cancers. These generally have low mortality, although squamous cell cancer accounts for the majority of skin cancer deaths in very elderly men and blacks. However, no studies have demonstrated that screening improves the outcome of melanoma or non-melanoma skin cancers. Although melanoma is a deadly cancer, there is evidence that the thinner it is when detected, the more amenable it is to resection and cure. Periodic total-body skin examination can increase the detection of thinner (earlier stage) melanoma; however, controlled studies are needed to determine whether early detection would actually have an important effect on mortality.
Primary care physicians identify substantially more benign lesions as suspicious compared with dermatologists, and are only slightly less likely to recognize the characteristics of a melanoma. In the absence of recommendations for population-based screening, it is anticipated that the majority of cases could be detected by a primary care physician.
Melanoma is the sixth leading cause of cancer death in the United States and its incidence is increasing rapidly in the United States. It is true that the yield for screening is low, but other established screening programs (e.g., screening for phenylketonuria in newborns) also detect rare conditions. Studies of population-based screening find that zero to nine per 100 people are found to have “suspected” melanoma. Confirmed diagnosis of melanoma and melanoma in situ occur in one to four per 1,000 people screened with one to five per 100 cases of nonmelanoma skin cancer. One review estimated that about 21,000 people would have to be screened to prevent one skin cancer death.2 To better determine the utility of population-based screening for melanoma, a large randomized trial of 600,000 subjects is being undertaken in Australia, but results will not be available in this decade.
1. Jackson A, Wilkinson C, Ranger M, Pill R, August P. Can primary prevention or selective screening for melanoma be more precisely targeted through general practice? A prospective study to validate a self-administered risk score. BMJ. 1998;316:34–8, discussion :38–9.
2. Elwood JM. Screening for melanoma and options for its evaluation. J Med Screen. 1994;1:22–38.
The case study and answers to the following questions on screening for skin 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 2001 and is an update of the 1995 recommendation on skin cancer screening. 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.ahrq.gov/clinic/uspstfix.htm); through the National Guideline Clearinghouse™ (www.guideline.gov); and in print through the AHRQ Publications Clearinghouse (800-358-9295) and the April 2001 Supplement to the American Journal of Preventive Medicine. Specific journal references cited in the answers are provided in the discussion.Answers appear on the following page.This case study is part of AFP's CME. See “Clinical Quiz” on page 1269.
Copyright © 2002 by the American Academy of Family Physicians.
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