New research published online by the British Medical Journal (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 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.
Researchers 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.
Between 1986 and 2001, the average biopsy rate across the nine areas 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 of disease, 1000 additional biopsies were associated with 6.9 extra melanoma cases diagnosed. The extra cases were confined to early stage cancer, yet mortality remained stable.
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.
As with all observational research, this study has several limitations, but this pattern suggests overdiagnosis, they conclude.