Does Screening for Skin Cancer Result in Melanoma Overdiagnosis?

Veronica Hackethal, MD

January 14, 2021

When the COVID-19 pandemic first hit, cancer screening in the US came to an abrupt halt. That experience, coupled with the financial fallout of the pandemic, has led some doctors to reassess business as usual.

In particular, a trio has taken aim at skin cancer screening — arguing that it should stop — in a 'sounding board' commentary published online January 7 in the New England Journal of Medicine.

"The COVID-19 pandemic has functionally stopped skin cancer screening; what is important is not to restart it," say the authors, led by H. Gilbert Welch, MD, MPH, Brigham and Women's Hospital, Boston, Massachusetts. Welch has often raised questions about cancer screening and highlighted the issue of overdiagnosis.

In this latest essay, Welch has teamed up with pathologist Benjamin Mazer, MD, Yale University, New Haven, Connecticut, who writes commentaries for Medscape, and dermatologist Adewole S. Adamson, MD, University of Texas, Austin, to argue that screening for skin cancer has led to an overdiagnosis of melanoma.   

However, two melanoma experts approached by Medscape Medical News point out flaws in some of their arguments, and say the issue is more nuanced that they present.

Arguing That Melanoma Is Overdiagnosed

The incidence of melanoma is six times as high as it was 40 years ago, making it the third most common cancer in the US, they point out. However, while case rates have skyrocketed, death rates from melanoma have remained about the same, which points to overdiagnosis, they argue.

They describe a cycle of increased diagnostic scrutiny that is driving overdiagnosis of melanoma. This includes heightened awareness (perhaps overly) among patients, widespread skin screenings, lower clinical thresholds for biopsy, and lower thresholds among pathologists for diagnosis of melanoma. Fear of missing cancer, legal concerns, and financial incentives may all contribute.  

"We view the rise in the incidence of melanoma as a sentinel event, a warning that an epidemic of inspection, surveillance, and biopsy of pigmented skin lesions is permeating through the general population," they write.

Furthermore, overdiagnosis could contribute to unnecessary intervention.

Between 2004 and 2017, rates of biopsy among fee-for-service Medicare recipients almost doubled (from 5% to 8%), according coding trends data cited in the article. Overdiagnosis and unnecessary intervention could cause psychological, financial, and physical harm to the patient, and the authors argue for interrupting the cycle.

"The most important step to break the cycle of melanoma overdiagnosis is to stop population-wide screening for skin cancer," they write.

The US Preventive Services Task Force currently states that there is insufficient evidence to weigh the balances vs harms of skin cancer screening, leaving it open to interpretation.

 "[T]he increase in melanoma diagnoses by a factor of 6, with at least an order of magnitude more persons undergoing a biopsy and no apparent effect on mortality, is more than enough to recommend against population-wide screening," Welch and colleagues conclude.

But the issue may be more nuanced, argues a melanoma expert.

"Everyone agrees that screening high-risk groups has the greatest chance of reducing cancer mortality. In melanoma, the strongest risk factor is the number of moles and presence of clinically atypical moles," David Polsky, MD, PhD, commented in an email. Polsky is a professor of dermatologic oncology at the Perlmutter Cancer Center at NYU Langone Health in New York City.

However, population-based studies have shown that at least half of melanoma patients are not considered high risk based on the appearance of the mole, he explained.

"Studies to identify genetic risk factors for melanoma have not yet progressed to the point where these can be tested in the clinic. We clearly have a knowledge gap that needs to be addressed," he said.

Moreover, it's not easy to predict which early melanomas will metastasize, said dermatologist Jennifer Stein, MD, PhD, who specializes in treating patients at high risk for melanoma at NYU Langone.

"This paper suggests that it may not be important to detect and treat melanoma in situ, and that the increase in diagnosis of melanoma in situ has led to more harms than good," she said. "There is evidence that most melanomas do originate as in situ lesions. Unfortunately, we cannot predict which ones will become more aggressive. For this reason, we treat melanoma in situ."

Taking Issue With Some of the Arguments

Both experts approached for comment take issue with several of the arguments put forward by Welch and colleagues in their essay.

For instance, Welch and colleagues cite research suggesting that UV light is a weak risk factor for melanoma, but Polsky disagrees. "There are many lines of evidence ranging from epidemiological, clinical, and biological studies that prove the causative association between ultraviolet light and melanoma, while acknowledging that other factors, such as genetic predisposition, play an important role," he said.

"Since ultraviolet light in the form of outdoor sunburns or indoor tanning exposure are modifiable risk factors, it is important that we continue with our current public messaging on their causal role in the development of melanoma."

Furthermore, the 2012 study that the authors cite to support their argument that pathologists today are more likely to diagnose melanoma than in years past is flawed, according to Stein. The study was very small and included just nine contemporary pathologists. Unlike in real life, pathologists in the study could not diagnose lesions as "atypical," and may have erred on the side of caution by calling them malignant, she cautioned.

"There were multiple limitations to this study that were acknowledged by its authors, who stated that it was a hypothesis-generating study and may not be generalizable," Stein said.

In addition, Polsky takes issue with the suggestion that awareness about melanoma among the general public is overly heightened.

"Reducing melanoma awareness would not be wise," he said. "Studies have shown that that awareness of melanoma is associated with the diagnosis of earlier-stage lesions that can be cured by simple skin surgery, without the need for more costly interventions utilized for more advanced melanomas."

Mazer reports travel compensation from Hillcrest Healthcare Systems, and is a commentator for Medscape. Welch has written three books on the subjects of overdiagnosis and testing for cancer. Adamson has disclosed no relevant financial relationships.

N Engl J Med. Published online January 7, 2021. Commentary

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