New research published online by the BMJ today (Thursday 4 August 2005)suggests that melanoma is being overdiagnosed in the United States.
The incidence of melanoma of the skin is rising faster than anyother major cancer in the United States. In 2002 -- the most recent yearof data -- the incidence was about six times that in 1950, but somedermatologists suspect that this rise may reflect more skin biopsies,not more disease.
Researchers examined skin biopsy rates between 1986 and 2001among people aged 65 and older in nine geographical areas of the US.They also measured incidence rates for melanoma for the samepopulation.
Between 1986 and 2001, the average biopsy rate across the nineareas increased 2.5-fold, from 2847 to 7222 per 100,000 population.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 ofdisease, 1000 additional biopsies were associated with 6.9 extramelanoma cases diagnosed. The extra cases were confined to early stagecancer, yet mortality remained stable.
Because these extra cases were virtually all early stagecancers and because the overall melanoma death rate remained stable,these findings suggest that the increased incidence of melanoma islargely the result of increased diagnostic scrutiny - that is, skinlesions are being biopsied that would not have been in the past, saythe authors. They also suggest that the true occurrence of melanoma hasnot changed.
As with all observational research, this study has several limitations, but this pattern suggests overdiagnosis, they conclude.
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