PROVIDENCE, R.I. -- Occurrence rates for cutaneous T-cell lymphoma more than tripled from 1973 to 2002, with the rise varying by race, sex, and geographic area, researchers found.
PROVIDENCE, R.I., July 17 -- Occurrence rates for cutaneous T-cell lymphoma more than tripled from 1973 to 2002, with the rise varying by race, sex, and geographic area, researchers found.
The cause of the "alarming" climb for this rare cancer, which includes mycosis fungoides and Szary syndrome, is unknown, Vincent D. Criscione, A.B., and Martin A. Weinstock, M.D., Ph.D., of Brown University and the VA Medical Center here, wrote in the July issue of the Archives of Dermatology.
A total of 4,783 new cases were diagnosed from 1973 through 2002, with an increase in each decade, they found in data from 13 population-based cancer registries of the Surveillance, Epidemiology, and End Results (SEER) program of the National Cancer Institute, representing 14% of the U.S. population.
The overall annual age-adjusted incidence of cutaneous T-cell lymphoma was 6.4 per million, with an increase in the annual incidence of 2.9 per million per decade over 30 years.
The rate amounted to 0.14% of all cancers and 3.9% of non-Hodgkin's lymphomas, they reported.
The incidence was higher among blacks (9.0 per million) than among whites (6.1 per million), and was higher among men (8.7 per million) than among women (4.6 per million).
The racial differences in incidence decreased with age, while the sex differences increased with age and decreased over time. These differences, the researchers said, may be of etiologic importance.
The incidence correlated with high physician density, high family income, high percentage of population with a bachelor's degree or higher, and high home values. These personal and geographic differences in incidence may be related, to some degree, to differences in access to medical care, the researchers noted.
The San Francisco registry had the highest rates, with 9.7 per million persons among whites and 10.8 per million among blacks. The Iowa registry had the lowest rates, with 3.7 per million among white individuals and 5.8 million among blacks. The incidence was also highest among the 13 SEER registries for the period 1992 through 2002 (14.9 per million).
Several studies have suggested that infectious agents (viruses such as Epstein Barr and human herpesvirus 6) and bacteria (staphylococcal superantigen) or environmental exposure may play a role in causing the disease.
Although the unusual geographic differences seen in these data could be explained by an environmental or viral exposure, the data neither directly support nor contradict such hypotheses, the researchers said.
Changes in the International Classification of Diseases for Oncology (ICD-O) morphologic definitions have redistributed these cases among specific subclassifications, making it difficult to evaluate incidence trends for categories such as mycosis fungoides, the researchers said.
In addition, they said, these changes created ambiguous histologic codes, which may have caused coding errors. These errors along with the lack of independent verification are limitations of this study. An epidemiological investigation using population-based data is important to better understand this disorder, they added.
This population-based study provides updated trends in
the U.S. incidence of the cancer and describes patterns that have not been reported previously. "These data may be useful in planning public health strategies, identifying risk factors, and understanding the etiology of this cancer so that it may some day be prevented," the investigators concluded.
In an accompanying editorial, Stuart R. Lessin, M.D., of the Fox Chase Cancer Center in Philadelphia, and a director of the foundation that funded the study, wrote that the increase in the incidence of cutaneous T-cell lymphoma in the U.S. parallels an increase in patient involvement in study advocacy.
In 1996, an online support group for patients with this malignancy was established. From this support group emerged the Cutaneous Lymphoma Foundation, a patient-advocacy group.
This study also demonstrates the clear need to codify lymphoma classification in tumor registries, including SEER, to improve the accuracy of classification, Dr. Lessin added.
Dr. Lessin is chairman of the Medical Advisory Board and a member of the Board of Directors of the Cutaneous Lymphoma Foundation.