Analyses of Lymphoma Incidence Trends by Subtype Suggest Priorities for Future Research

NCI researchers found striking differences in incidence patterns and time trends by lymphoma subtype, age, sex, and race/ethnic group in a large U.S. population-based assessment published in the January 1 issue of Blood.

Although lymphoma is the fifth most common category of neoplasms in the United States, the causes of this group of diseases are largely unknown, noted scientists from NCI's Division of Cancer Epidemiology and Genetics (DCEG). The researchers analyzed almost 115,000 lymphoma cases diagnosed between 1992 and 2001 in 12 Surveillance, Epidemiology, and End Results (SEER) registries. The researchers used the 2001 World Health Organization lymphoma classification system in their analysis.

"Analyses of the incidence patterns and trends of the lymphoma subtypes in the general population can provide us with clues regarding etiology and suggest promising areas for future research," said Dr. Lindsay Morton, DCEG research fellow and lead author on the study.

For example, during the 10-year period, rates of diffuse large B-cell lymphoma and follicular lymphoma in the elderly increased 1.4 percent and 1.8 percent per year, respectively, whereas rates for chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL) declined 2.1 percent per year, suggesting that exposures to the still unknown causes of these lymphoma subtypes may have changed. The investigators also noted variation in the incidence of lymphoma subtypes by age. "These age differences suggest that the timing of key exposures may differ by subtype," Dr. Morton noted.

The study also included the first comprehensive analysis of lymphoma incidence patterns among Asian Americans, showing considerably lower rates for CLL/SLL and Hodgkin lymphoma. In contrast, whites had the highest burden for most subtypes, especially hairy cell leukemia and follicular lymphoma, whereas African Americans had the highest rates for plasma cell and T-cell lymphomas. Source: Latest NCI Newsletter