Incidence of Melanoma May Be Result of Overdiagnosis

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Melanoma

Is melanoma being overdiagnosed? New research by a team from the Center for the Evaluative Clinical Sciences at Dartmouth Medical School (DMS) and the VA Outcomes Group at the Veterans Affairs Medical Center, suggests that an apparent rise in melanoma cases may in fact be a result of overscreening and overdiagnosis.

The study, led by H. Gilbert Welch, MD, MPH, a professor of medicine at DMS and the VA Outcomes Group, appears in the current issue of the British Medical Journal. Welch and colleagues Lisa M. Schwartz and Steven Woloshin examined skin biopsy rates between 1986 and 2001 among people aged 65 and older in nine geographical areas of the US. They also measured incidence rates for melanoma for the same population.

The incidence of melanoma of the skin is rising faster than any other major cancer in the United States. In 2002, the most recent year of data, the incidence was about six times that in 1950, but some dermatologists suspect that this rise may reflect more skin biopsies, not more disease. Welch and colleagues noted that death rates from melanoma have remained stable since 1986; what has increased during that time, they report, is the rate of skin biopsies.

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Between 1986 and 2001, the average biopsy rate across the nine areas increased 2.5-fold, from 2847 to 7222 per 100,000 population, the study found. Over this time, the average incidence of melanoma increased 2.4-fold, from 45 to 108 per 100,000 population.

Even after assuming an increase in the true occurrence of disease, 1000 additional biopsies were associated with 6.9 extra melanoma cases diagnosed.

Because these extra cases were virtually all early stage cancers and because the overall melanoma death rate remained stable, these findings suggest that the increased incidence of melanoma is largely the result of increased diagnostic scrutiny - that is, skin lesions are being biopsied that would not have been in the past, say the authors. They also suggest that the true occurrence of melanoma has not changed.

Welch is the author of "Should I Be Tested for Cancer? Maybe Not and Here's Why," published in 2004 by the University Of California Press.

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