Monday, February 8, 2021

Are primary care physicians overdiagnosing cutaneous melanoma?

 - Kenny Lin, MD, MPH

In an editorial in the February 1 issue of AFP, Dr. Jenny Doust and colleagues wrote about the problem of widening disease definitions, a common phenomenon in which the definition of a disease is "broadened over time to include milder and earlier cases," leading to harm "by exposing more patients to the adverse effects of treatments, triggering investigation and prescribing cascades, increasing anxiety, and placing a financial burden on patients and the wider society." Expanding the number of patients diagnosed with disease increases the burden on primary care physicians called on to manage these additional cases, even when it is uncertain if earlier interventions prevent morbidity or mortality. Illustrative examples of wider disease definitions include hypertension, polycystic ovary syndrome, breast cancer, and autism. What can family physicians do about it? The authors responded:

Recognizing the problem is the first step in tackling it. In particular, family physicians should not blindly accept new definitions and testing guidelines without an adequate understanding of the harms and benefits of the changes and the implications for our patients and wider practice.

Along similar lines, a recent analysis in the New England Journal of Medicine by Dr. H. Gilbert Welch and colleagues examined the drivers of the dramatically increased incidence of cutaneous melanoma in the U.S., which today is 6 times as high as in 1975 despite essentially no change in melanoma mortality. They pointed out that exposure to ultraviolent (UV) radiation (including tanning bed use) cannot account for more than a small portion of this increase. Instead, they argued that increased diagnostic scrutiny - "the combined effect of more screening skin examinations, falling clinical thresholds to biopsy pigmented lesions, and falling pathological thresholds to label the morphologic changes as cancer" - is most likely to be responsible for the epidemic of new diagnoses. Not only has the annual percentage of fee-for-service Medicare beneficiaries undergoing skin biopsies nearly doubled since 2004, but pathologists frequently upgraded skin biopsy specimens obtained in the late 1980s from benign to malignant when evaluating the same specimen two decades later. Primary care physicians contribute to widening the definition of cutaneous melanoma by performing or referring for biopsy small (<6 mm), incidentally detected skin lesions and screening patients with dermoscopy, which identifies more melanomas than visual inspection alone but is not well studied in primary care settings.

The U.S. Preventive Services Task Force (USPSTF) has concluded that current evidence is insufficient to assess the balance of benefits and harms of skin cancer screening in asymptomatic adults. Nonetheless, more than half of family physicians and general internists in a 2011 survey reported performing full-body skin examinations for skin cancer screening. In a 2020 AFP editorial, Drs. Michael Pignone and Adewole Adamson (Dr. Adamson also co-authored the NEJM analysis) observed that "compared with usual care, potential effects of screening on morbidity and mortality from keratinocyte carcinoma are at most small, and screening cannot be justified based on the impact on keratinocyte carcinoma alone." Dr. Welch and colleagues went one step further, arguing that the established harms of skin cancer screening already outweigh any potential benefits:

The 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. ... It [screening] has been effectively promoted under the guise of public health, with the combination of frightening messages about skin cancer and the premise that screening can only help. However, medical care should be driven by patient needs, not system needs. Now is not the time to add more anxiety and expense to an already anxious and expensive world.

Not surprisingly, dermatologists have a more positive view of skin cancer screening, as reported in a news story about the analysis by Dr. Welch and colleagues that quoted the president of the American Academy of Dermatology as stating that "an aggressive approach to prevention and treatment is entirely appropriate for a disease that kills 20 Americans each day." Of course, no one is urging clinicians to stop counseling patients on minimizing their exposure to UV radiation; indeed, the USPSTF recommends behavioral counseling to prevent skin cancer, particularly for children, their parents, and young adults. But screening for skin cancer, which has effectively widened the definition of cutaneous melanoma and driven widespread overdiagnosis - is a different story. To give Dr. Doust and colleagues the last word: "We [primary care physicians] are not here to passively enact specialist recommendations. Instead, we need to more assertively act as advocates for our patients and our communities."