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Skin Cancer, Screening, 2016

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Recommendations: Screening for Skin Cancer

Discussion:

Scope of Review

The USPSTF commissioned a systematic evidence review,34 to update its 2009 recommendation on screening for skin cancer. The review addressed several questions about screening for skin cancer with the clinical visual skin examination, including its effectiveness in reducing skin cancer morbidity and mortality and death from any cause; its potential harms, including any harms resulting from associated diagnostic follow-up; its test characteristics when performed by a primary care clinician versus a dermatologist; and whether its use leads to earlier detection of skin cancer compared with usual care.3 Unlike in the previous review, the evidence concerning patient self-examination for skin cancer was not included in this statement. The visual skin self-examination will be addressed in a separate recommendation statement on counseling to prevent skin cancer.

Accuracy of Screening Tests

A systematic review of 11 studies on the diagnostic accuracy of screening by primary care clinicians and dermatologists identified during the previous evidence review found that screening by primary care clinicians had a sensitivity of 42% to 100% and a specificity of 98% for the diagnosis of melanoma.12 Since then, 2 additional studies on the test characteristics of the clinical visual skin examination have been published: 1 evaluating screening performed by primary care clinicians and 1 evaluating screening performed by dermatologists or plastic surgeons. These studies found that sensitivity ranged from 40% to 70%, which sharply decreased as the length of follow-up increased (from 12 to 24 or 36 months). Specificity ranged from 86% to 98%.31314 None of the studies could draw reliable conclusions as to whether screening performed by any of the clinical specialties differed in diagnostic accuracy.312-14

Effectiveness of Early Detection and Treatment

No RCT has directly evaluated the effectiveness of the clinical visual skin examination for reducing skin cancer morbidity or mortality (a pilot study by Aitken et al in Queensland, Australia, began in 2002, but a full trial was never completed).3 A single fair-quality ecologic study (SCREEN) compared trends in melanoma mortality rates in 1 region of Germany using a population-based skin cancer awareness campaign, clinician education and training, and clinical visual skin examination provided through a cancer screening program with several surrounding regions that did not have similar interventions available. After a 2-year public skin cancer awareness campaign, 360,288 adults 20 years and older (about 19% of the eligible population) received a single clinical visual skin examination. After 10 years, the study found a 48% relative reduction in the risk of dying from melanoma in the region that instituted the interventions compared with the control regions, which translates into an absolute reduction of 1 fewer death from melanoma per 100,000 persons screened.15The SCREEN study has several important limitations. First, it does not provide individual patient-level data on the effect of the clinical visual skin examination, and as an ecologic observational study, it is subject to the potential effects of known and unknown biases and confounders. Second, the separate effects of the public education component cannot be disentangled from those of the clinical visual skin examination component; therefore, it is likely that the effect of screening alone is smaller than estimated. In addition, the melanoma mortality rate in the region receiving the interventions was already declining prior to the introduction of the cancer screening program. This also suggests that the 48% relative reduction overestimates the true effect size of screening. Several other data points raise questions about the plausibility of the observed effect: 1) only 19% of the total eligible population was actually screened, and 37% of these individuals were lost to follow-up, yet the relative magnitude of the mortality reduction in the population is larger than in almost any other cancer screening intervention currently available; and 2) three-fourths of the population screened were women, yet equal reductions in melanoma mortality were observed among both men and women.15 Furthermore, an independent study evaluating an additional 5 years of follow-up in the SCREEN study population found that the observed reduction in melanoma mortality rates did not persist over time but essentially returned to the baseline rates observed before the screening program was initiated (Figure).6When direct, overarching evidence concerning the benefit of a screening intervention on health outcomes is inconclusive, the USPSTF looks to a chain of indirect evidence to assess the effectiveness of the preventive service. In the case of the clinical visual skin examination, this includes linking together information about the ability of screening to detect melanoma earlier than in usual care and the link between earlier detection of skin cancer and resultant morbidity and mortality. The USPSTF identified only 1 fair-quality case-control study pertaining to the question of whether screening for skin cancer with a clinical visual skin examination leads to the earlier detection of melanoma compared with usual care.3 It found a modest association between the clinical visual skin examination and early detection (odds ratio, 0.84 [95% CI, 0.75 to 0.98]).16 However, because the study used patient self-report to identify exposure to clinician skin examination, recall bias is a potential concern.

Harms of Early Detection and Treatment

Evidence on the harms of the clinical visual skin examination is limited.3 In the SCREEN study, approximately 4.4% of screened individuals (1 of 23 participants) underwent a skin excision for a suspicious lesion. The majority of these biopsies did not result in a cancer diagnosis. Overall, for both men and women, 1 case of melanoma was detected per 28 excisions performed. However, this varied greatly by patient age. For example, among men aged 20 to 34 years versus 65 years and older, 1 case of melanoma was detected per 52 versus 20 skin excisions, respectively.7Cosmetic or, more rarely, functional adverse effects may also result from an excisional biopsy prompted by clinical visual skin examination, although there are few data available on the frequency or specific details of these events. One fair-quality study of a single physician’s performance of skin cancer screening and razor-blade shave biopsy among patients who were not ultimately diagnosed with skin cancer found that 7% of these patients expressed poor satisfaction with the cosmetic results (whereas the physician felt the results were poor in 16% of cases).317Overdiagnosis and overtreatment—the identification and treatment of cancer that would never have harmed the patient in the absence of screening—is also a potential outcome of concern. It is not possible to directly determine for any individual patient whether a diagnosed cancer will progress or not; as such, measuring overdiagnosis is not a straightforward process and must be indirectly quantified. In the case of skin cancer, there is limited research to estimate the potential magnitude of the burden of overdiagnosis associated with screening. An ecologic study linking melanoma incidence and mortality data from the National Cancer Institute’s Surveillance, Epidemiology, and End Results Program with Medicare claims for skin biopsy among patients 65 years and older found that from 1986 to 2001, the average incidence of melanoma increased 2.4 times (from 45 to 108 cases per 100,000 persons), while the average biopsy rate increased 2.5 times (from 2847 to 7222 biopsies performed per 100,000 persons). However, the increased cancer incidence was entirely due to extra cases of in situ and local disease, without the expected complementary decrease in the incidence of advanced melanoma or death from melanoma. The authors concluded that this pattern strongly suggested that screening efforts in the United States were generating overdiagnosis, rather than depicting a true increase in the occurrence of melanoma.8

Estimate of Magnitude of Net Benefit

Evidence to assess the net benefit of screening for skin cancer with the clinical visual skin examination is limited. Direct evidence on the effectiveness of screening in reducing melanoma morbidity and mortality is limited to a single fair-quality ecologic study with important methodological limitations. This study suggests that, at best, a program of public education and disease awareness coupled with 1-time visual skin examination by a clinician may reduce the risk of dying from melanoma among average-risk adults by about 1 death per 100,000 persons screened after 10 years; however, there are reasons to believe that the effect size is likely smaller. The indirect pathway of evidence (ie, examining the accuracy of screening; link between visual skin examination and earlier detection of melanoma, such as lesion thickness; and the link between earlier detection of melanoma and skin cancer–related morbidity and mortality) and the studies included as part of this pathway are subject to several important biases of screening, including lead-time bias and length-biased sampling. These biases preclude the USPSTF’s ability to draw reliable conclusions about the efficacy of the clinical visual skin examination with reasonable certainty. Therefore, there is insufficient evidence to reliably conclude whether screening for skin cancer with a clinical visual skin examination reduces melanoma morbidity or mortality.Information on harms is similarly sparse. The potential for harm clearly exists, including a high rate of unnecessary biopsies, possibly resulting in cosmetic or—more rarely—functional adverse effects, and the risk of overdiagnosis and overtreatment. It is difficult for the USPSTF to accurately bound the magnitude of these potential harms without better information about the frequency with which skin cancer is likely overdiagnosed and overtreated. Further, it is challenging for the USPSTF to correctly bound the magnitude of the net benefit without more accurate and precise information about the size of the potential mortality benefit, if one exists. As such, the USPSTF concludes that the evidence is insufficient to assess the balance of benefit and harms of screening for skin cancer in adults with a clinical visual skin examination.

Response to Public Comment

A draft version of this recommendation statement was posted for public comment on the USPSTF website from December 1 through December 28, 2015. In response to the comments received, the USPSTF added a reference to a study that examined longer-term melanoma mortality rates in the SCREEN study population.6 The USPSTF also clarified that the recommendation does encompass all forms of skin cancer (ie, squamous and basal cell carcinoma and melanoma). A clinical visual skin examination will detect all skin cancer types; however, in assessing the potential benefit of screening, the USPSTF focused on melanoma because the associated morbidity and mortality rates for this type of skin cancer are substantially greater than for the others. In addition, although the systematic evidence review searched for studies of all skin cancer types, the evidence that met the prespecified inclusion criteria for the review only described efficacy outcomes for melanoma.Several comments stressed that the USPSTF should place greater emphasis on the benefits of detecting and treating nonmelanoma skin cancer, noting the risk for such cancer to become locally destructive and lead to disfigurement if left untreated. Although the USPSTF agrees that reduced morbidity from nonmelanoma skin cancer or its requisite treatment would be an important benefit of screening, there is currently no evidence available to address this outcome for the clinical visual skin examination. It is therefore unknown whether there is an incremental benefit to detecting nonmelanoma skin cancer through a program of regular visual clinical examination versus patient self-identification as part of general body awareness followed by reasonably prompt evaluation by a clinician.Several comments suggested that the USPSTF should consider making a separate positive recommendation for persons who are at increased risk for skin cancer (eg, those with a family history of melanoma), as they may potentially benefit more from a screening intervention. At present, there is insufficient evidence for any population that regular visual skin examination by a clinician can reduce skin cancer–related morbidity and mortality; the USPSTF agrees that targeted research among populations with the highest burden of disease would be useful.

Other Sections:

Research Needs and Gaps

The USPSTF recognizes the challenge of conducting a definitive randomized clinical trial (RCT) on primary screening, with cause-specific mortality as an end point, to provide clear evidence on the efficacy of the clinical visual skin examination in screening for skin cancer, given the comparatively low rate of death from melanoma in the population (even among persons at higher risk). If adequately powered RCTs are not possible, a high-quality case-control study could provide sufficient power without requiring a large sample size. However, this study design has limitations in the ability to create an appropriate comparison group, the ability to accurately measure the exposure of interest (because of recall bias and other sources of misclassification), healthy volunteer bias (persons receiving skin examinations likely have other good health habits), and other unmeasured sources of confounding. Studies would have to be carefully designed to avoid these threats to validity. Despite these challenges, the USPSTF concludes that further evidence is necessary to advance the field on this essential question. An optimized version of the SCREEN study (ie, a time-series study), in which the clinical visual skin examination alone, without the potential confounding of a second intervention, is evaluated, would also be useful. Additional research on the possible harms of screening for skin cancer—particularly the potential for overdiagnosis and overtreatment—is also needed to help fully understand the ultimate net benefit of the clinical visual skin examination.

Update of Previous USPSTF Recommendations

This recommendation updates the 2009 USPSTF recommendation.18 The USPSTF has again concluded that the current evidence is insufficient to assess the balance of benefit and harms of screening for skin cancer in adults with a clinical visual skin examination. However, the USPSTF decided to no longer include a statement about patient skin self-examination in the current recommendation. This intervention will be addressed in the USPSTF’s update of its recommendation statement on counseling to prevent skin cancer.

Recommendations of Others

Most professional organizations in the United States have no specific recommendations about screening for skin cancer with the clinical visual skin examination. The American College of Physicians has no current guidance on skin cancer screening performed by a clinician, nor does the American College of Preventive Medicine (the latter has an archived statement from 199819). The American Academy of Family Physicians concludes that the current evidence is insufficient to assess the balance of benefit and harms of visual skin cancer screening in adults.20 The American Academy of Dermatology does not have formal guidelines on skin cancer screening, although it does encourage and provide resources for its physician members to hold free skin cancer screening events for the public.21 The American Cancer Society recommends that adults 20 years and older who receive periodic health examinations should have their skin examined as part of a general cancer-related checkup.22

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