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Task force: Evidence insufficient to recommend skin cancer screening
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Evidence is insufficient to determine whether the potential benefits of routine full-body skin cancer screenings for average-risk adults outweigh the potential harms, according to a recommendation statement from the U.S. Preventive Services Task Force.
Evidence that assesses the net benefit of skin cancer screening via clinician visual skin examination is limited, and the evidence to support the effectiveness of screening for reducing mortality and morbidity of melanoma — the deadliest form of skin cancer — “is limited to a single fair-quality ecologic study with important methodological limitations,” the task force concluded.
“[Meanwhile], 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 overdiagnosis and overtreatment,” the recommendation statement read.
The conclusion mirrors the one the task force reached in its last skin cancer screening recommendation, issued in 2009.
Evidence review
An estimated 76,380 new cases of melanoma will be diagnosed this year in the United States, and an estimated 10,100 Americans will die of the disease, according to NCI.
Melanoma accounts for the majority of skin cancer-related deaths. Nonmelanoma skin cancers, such as basal cell carcinoma and squamous cell carcinoma, rarely result in substantial morbidity and account for less than 0.1% of skin cancer deaths.
Karen J. Wernli
Karen J. Wernli, PhD, MS, assistant investigator with Group Health Research Institute at Kaiser Permanente Research Affiliates Evidence-based Practice Center in Seattle, and colleagues conducted a systematic review of clinical skin cancer screening among adults on behalf of the U.S. Preventive Services Task Force (USPSTF).
Researchers used the MEDLINE and PubMed databases, as well as the Cochrane Register of Controlled Trials, to identify relevant studies published from Jan. 1, 1995, through June 1, 2015.
Primary outcomes included melanoma incidence and mortality, stage distribution, diagnostic accuracy of cancer screening and harms from screening.
Wernli and colleagues identified 13 unique fair- or good-quality studies, none of which were randomized clinical trials. In these studies, they found limited evidence on the association between skin cancer screening and mortality.
An ecologic study performed in Germany (n = 360,288) determined population-based skin cancer screening reduced melanoma deaths among average-risk adults by 0.8 per 100,000 people screened after 10 years. In five comparison regions, melanoma mortality remained unchanged or increased slightly.
The number of excisions needed to detect one skin cancer varied by sex and age.
Twenty-two excisions were required to detect one melanoma among women aged 65 years and older, whereas 41 excisions were needed to detect one melanoma among women aged 20 to 34 years. Researchers reported similar patterns among men, as well as for detection of nonmelanoma skin cancers.
When primary care physicians performed visual skin examinations (n = 16,383), sensitivity to detect melanoma was 40.2% and specificity was 86.1%. When dermatologists performed visual skin examinations (n = 7,436), sensitivity was 49% and specificity was 97.6%.
“The screening accuracy of dermatology and primary care clinicians could not be directly compared because of differences in time to ascertainment of cancer outcomes that affect screening examination performance measures,” Wernli and colleagues wrote.
One case–control study of melanoma (n = 7,586) showed individuals diagnosed with lesions greater than 0.75 mm thick had an OR of 0.86 (95% CI, 0.75-0.98) for receipt of physician skin examination in the previous 3 years compared with controls.
A review of eight cohort studies (n = 236,485) revealed a statistically significant association between melanoma mortality and the degree of disease involvement at diagnosis. The association persisted regardless of lesion thickness or disease stage.
Researchers also determined tumor thickness greater than 4 mm was associated with increased risk for melanoma mortality, and late stage at diagnosis increased risk for all-cause mortality.
“A substantial body of evidence consistently suggests that later stage and increasing skin lesion thickness at melanoma detection is associated with increased melanoma and all-cause mortality risk,” Wernli and colleagues wrote. “However, the evidence for an association between skin cancer screening and melanoma mortality is limited.”
Recommendation statement
The results led the USPSTF to give an “I” recommendation for visual skin examination by clinicians, indicating the evidence to assess potential benefits vs. risks is insufficient.
Although the study conducted in Germany showed screening reduced risk for death by about one per 100,000 people screened after a decade, the effect size likely is smaller, task force members concluded.
In addition, indirect evidence — including studies that analyzed accuracy of screening, the association between visual skin examination and earlier detection of melanoma, and the association between earlier detection and mortality and morbidity — “is subject to several important biases of screening, including lead-time bias and length-biased sampling,” the recommendation statement read.
“Information on harms is similarly sparse,” the statement continued. “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.”
Subgroups most likely to develop fatal melanoma may derive the greatest benefits from skin cancer screening and further research is needed to evaluate the effectiveness of targeted screening in these individuals, Wernli and colleagues wrote.
“Several algorithms use melanoma risk factors to qualify risk for melanoma and could have utility for screening programs in identifying individuals who might benefit most from screening,” they wrote. “However, none have been externally validated, and they are generally based on risk in people of white race. No evidence was identified to suggest these algorithms have been adopted in U.S. clinical practice. If externally validated, risk assessment tools might lead to evaluating a targeted screening approach.”
The USPSTF acknowledged it received considerable input during a public comment period that called on the task force to consider the potential value of making a separate positive recommendation for individuals who are at increased risk for skin cancer, such as those with a family history of melanoma.
The task force, however, opted not to do that.
“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 recommendation statement read. “The USPSTF agrees that targeted research among populations with the highest burden of disease would be useful.”
The USPSTF also decided against including a statement about self-skin examinations in its current recommendation. The task force plans to address this topic in a subsequent update of its recommendation statement on counseling to prevent skin cancer.
Patient implications
Many other medical organizations — such as the American College of Physicians and American College of Preventive Medicine — have not issued recommendations regarding skin cancer screening.
The American Academy of Family Physicians has concluded evidence is insufficient to make such a recommendation.
The American Academy of Dermatology — which has conducted free skin cancer screenings since 1985 — recommends people perform skin self-exams to check for signs of skin cancer and also get skin exams from their physician. The academy recommends those with a history of melanoma perform regular self-exams and also receive a full-body exam by a board-certified dermatologist at least once a year.
The American Cancer Society, meanwhile, recommends adults aged 20 years or older who receive periodic health examinations have their skin examined.
Eleni Linos
The USPSTF recommendation likely will leave national organizations disappointed, and patients and physicians confused, Eleni Linos, MD, PhD, assistant professor in the department of dermatology at University of California, San Francisco, and colleagues wrote in an accompanying editorial.
“However, the USPSTF recommendations are based on a rigorous evidence review that balanced the benefits and risks of screening,” Linos and colleagues wrote. “The potential benefits are apparent, but the risks — such as unnecessary procedures and their downstream complications — may not be.
“Overtreatment of skin cancer may be especially problematic for patients with limited life expectancy due to old age or comorbidities,” they added. “These patients may not live long enough to benefit from more intensive treatments but may be at risk for short-term treatment-related complications."
The recommendations are not downplaying the importance of skin cancer, Linos and colleagues emphasized.
“We need high-quality, long-term randomized clinical trials of the effectiveness of screening on skin cancer prevention,” they wrote. “Meanwhile, we should also fully implement skin cancer primary prevention by eliminating indoor tanning exposure, especially among youths, and increasing the use of sun-protection strategies that work.”
Hensin Tsao
The explanation behind the task force’s recommendation must be understood clearly, Hensin Tsao, MD, PhD, clinical director of the Massachusetts General Hospital Melanoma and Pigmented Lesion Center, and Martin A. Weinstock, MD, PhD, professor of dermatology and community health at Brown University, wrote in a separate editorial.
Martin A. Weinstock
“‘Insufficient evidence of benefit is different from ‘evidence of no benefit,” Tsao and Weinstock wrote. “The public, physicians and the popular press should avoid this misinterpretation. For the scientific community, the ‘I’ designation should not be viewed as an indictment but rather an invitation to the public health, medical and scientific communities to galvanize and to work together in executing well-designed but feasible studies so future recommendations can be of greater public health benefit.” – by Chelsea Frajerman Pardes and Mark Leiser
Linos E, et al. JAMA Intern Med. 2016;doi:10.1001/jamainternmed.2016.5008.
NCI. SEER Stat Fact Sheets: Melanoma of the Skin. Available at: seer.cancer.gov/statfacts/html/melan.html. Accessed July 27, 2016.
USPSTF. JAMA. 2016;doi:10.1001/jama.2016.8465.
Tsao H and Weinstock MA. JAMA. 2016;doi:10.1001/jama.2016.9850.
Wernli KJ, et al. JAMA. 2016;doi:10.1001/jama.2016.5415.
Disclosure: The researchers and USPSTF members report no relevant financial disclosures. Tsao reports honorarium from Lubax. Linos and Weinstock report no relevant financial disclosures.
Perspective
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Ashfaq A. Marghoob
Michael A. Marchetti
Allan C. Halpern
The U.S. Preventive Services Task Force (USPSTF) investigation concluded there is insufficient evidence to assess the balance of benefits and harms of visual skin examination to screen for skin cancer in the general population. This statement received much media attention — including an article in the July 26 edition of The New York Times — and spawned a lively debate with at least four editorials written in response.
It is important to underscore that the USPSTF statement pertains to asymptomatic adults. Targeted screening of individuals at elevated risk for skin cancer was not considered. Although many physicians working in the trenches with patients who have skin cancer were disappointed with the USPSTF statement, we agree its stance is not unreasonable based on the available literature. Although it may seem intuitive that a visual examination for skin cancer is safe and effective, there is a paucity of evidence to support this conclusion. The USPSTF statement should be considered a call to action for researchers to design studies to investigate the benefits of — as well as the potential harms from — screening. In fact, some researchers already have begun to address some of the issues raised by the USPSTF.
Most researchers agree that targeting the populations at highest risk for skin cancer has the greatest potential for showing that the benefits do, in fact, outweigh the harms. Once proven, future studies can be rolled out to include the general population.
Factors requiring attention in future studies have been alluded to by the USPSTF, as well as in the editorials written in response to the USPSTF statement. Some of the factors that require our attention regarding skin cancer surveillance include:
- Determining the morbidity, mortality and quality-of-life issues associated with delays in diagnosis;
- Determining the morbidity due to unnecessary biopsies of benign lesions;
- Estimating the degree of melanoma overdiagnosis and misdiagnosis associated with skin cancer screening, and the morbidity associated with overtreatment;
- Addressing whether the screening test should consist of the ABCDE rule — the acronym for which stands for asymmetry, border irregularity, color variegation, diameter greater than 6mm, and evolution — or whether it should include other features, such as the ugly duckling rule;
- Addressing what actually constitutes a skin cancer screening examination, and how such an examination should best be performed;
- Identifying which clinicians and physician extenders are equipped to perform visual skin cancer screening examinations;
- Addressing the operator-dependent variability in the sensitivity and specificity of the visual examination;
- Determining the value of augmenting the naked eye examination with dermoscopy or other instruments to augment cognition; and
- Determining the optimal screening interval.
Pending the results from additional studies, those of us in the trenches should focus initially on screening the highest-risk subset of the population, and we should educate clinicians and the public in early recognition of melanoma. With a concerted effort on the part of physicians, research likely will show that the benefits of screening outweigh its harms, at least in high-risk cohorts. Off to the trenches we go.
References:
Linos E, et al. JAMA Intern Med. 2016;doi:10.1001/jamainternmed.2016.5008.
Nahar VK, et al. JAMA Oncol. 2016;doi:10.1001/jamaoncol.2016.2440.
Swetter SM, et al. JAMA Dermatol. 2016;doi:10.1001/jamadermatol.2016.2606.
Tsao H and Weinstock MA. JAMA. 2016;doi:10.1001/jama.2016.9850.
USPSTF. JAMA. 2016;doi:10.1001/jama.2016.8465.
Weinstock MA, et al. Cancer. 2016;doi:10.1002/cncr.30177.
Wernli KJ, et al. JAMA. 2016;doi:10.1001/jama.2016.5415.
Laura Korb Ferris
When considering the U.S. Preventive Services Task Force’s “I” recommendation, it is important to realize what it does not mean. It does not apply to screening by dermatologists, nor to patients who are at higher risk for skin cancer or have lesions of concern. It is not a recommendation against skin cancer screening, but rather a statement that more evidence is needed to balance the benefits and harms of screening.
While weighing benefits and harms of screening, it is important to consider the significance of each. Unlike screening procedures that require exposure of the patient to radiation, an invasive procedure or even venipuncture, the visual examination used to screen for skin cancer carries essentially no risk to the patient. Even skin biopsy is low risk and, in a study cited in the task force’s report, more than 90% of patients and physicians were pleased with the cosmetic outcome of the biopsy scar. The harm of diagnosing melanoma at a more advanced stage, with a greater risk for mortality, greatly overshadows the potential harm of a skin biopsy.
The task force also cited concern about the harm of overdiagnosis of thin melanomas that may have little biologic significance. However, the majority of ultimately fatal melanomas are less than 1 mm in Breslow thickness at diagnosis. Until the biologic behavior of these thin melanomas can be predicted at diagnosis, the best chance for reducing melanoma mortality is through the prompt diagnosis and treatment of thin lesions.
The diagnosis of later-stage melanoma also affects cost. The nearly 10-fold difference in the cost of undergoing wide local excision alone vs. with sentinel lymph node biopsy was not considered in the task force’s report. Reducing the number of more advanced procedures performed likely would offset the cost of the additional relatively inexpensive skin biopsies that may be associated with population-based screening.
In 2014, at University of Pittsburgh Medical Center (UPMC), we began a large-scale primary care–based skin cancer screening program. We published a study showing there was not a significant increase in the proportion of patients who underwent skin surgery or visited a dermatologist after initiation of this program. Although this study was not part of the USPSTF review, it shows screening can be performed on a large scale without the harm of overutilization of health care resources. In the first year of the UPMC program, melanomas detected in screened individuals were thinner than those ultimately diagnosed in the unscreened population. Data from this screening program will be valuable in evaluating the benefits and harms of a large-scale skin cancer screening program in the United States.
Disclosure: Ferris reports no relevant financial disclosures.
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