WAIKOLOA, HAWAII The incidence of cutaneous T-cell lymphoma has risen dramatically since the early 1970s for reasons that are not known, Dr. Joan Guitart said at the annual Hawaii dermatology seminar sponsored by Skin Disease Education Foundation.
Moreover, the best available numbers probably underestimate the true incidence because of reporting delay. Diagnosis of early mycosis fungoides, which is the most common type of cutaneous T-cell lymphoma (CTCL), can be quite difficult as the disease often mimics psoriasis, eczema, and other benign dermatoses, he said.
"Clearly, in the future we will be seeing a lot more CTCL," predicted Dr. Guitart, professor of dermatology at Northwestern University, Chicago.
He cited a population-based study that was conducted by dermatoepidemiologists at Brown University, Providence, R.I. Utilizing registry data from the National Cancer Institute's Surveillance, Epidemiology, and End Results program, the investigators showed that the annual incidence of CTCL in the United States increased more than threefold from 1973 to 2002.
The researchers found marked racial differences in CTCL.
The annual incidence in blacks was 9.0 cases per 1 million, compared with 6.1 per million in whites. The disease was also substantially more common in men, with an annual incidence of 8.7 per million, compared with 4.6 per million in women.
The racial disparity diminished with age. In contrast, the difference between genders became more pronounced with advancing age but decreased over the course of the study period (Arch. Dermatol. 2007;143:8549).
The investigators identified substantial geographic differences in CTCL incidence that were consistent with theories holding that environmental or viral exposures may play an etiologic role in the disease.
They also found that higher CTCL rates were associated with indicators of greater socioeconomic status, including median family income, median home value, and percentage of the population with a bachelor's degree or higher, Dr. Guitart noted.
There was no association between the incidence of CTCL and population density, but rates were strongly correlated with physician density, said Dr. Guitart.
The researchers concluded that improved diagnostic tools for CTCL and changes in International Classification of Diseases for Oncology schemes over the years may have contributed to the rising patient numbers but are not sufficient to account for the bulk of the marked increase.
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The annual incidence of CTCLin the U.S. increased more than threefold from 1973 to 2002. DR. GUITART