In a large population-based study conducted on non-Hodgkin's lymphoma, researchers at the University of California, San Francisco found that exposure to certain environmental factors that affect the immune system could decrease a person's risk of developing the disease.
The two-part study included a total of 4100 participants, and results for 3376 of the population are published in the August 15 issue of the American Journal of Epidemiology.
"These findings are important because although there has been a steady increase in the incidence of non-Hodgkin's lymphoma, there are very few established risk factors," says Elizabeth Holly, PhD, MPH, UCSF professor in the department of Epidemiology and Biostatistics and lead author of the study. "They also are important because much of the data generated in this study is consistent with the role of activated macrophages in the pathogenesis of lymphoma."
Despite the lack of known risk factors for non-Hodgkin's lymphoma, its annual increase of nearly four percent among men and three percent among women has exceeded that of all other cancers except melanoma of the skin. The American Cancer Society estimates that 25,700 people will die of non-Hodgkin's lymphoma and 56,800 new cases will be diagnosed this year.
Lymphomas are an overexpression of B cells that are stimulated by activated T cells and activated macrophages, both components of the immune system. Macrophages stimulate the production and replication of B cells by driving T cell activation. Therefore, anything that affects this activation process might influence the rate of overproduction.
The researchers reported that factors associated with an increased risk of
non-Hodgkin's lymphoma include a history of splenectomy (5-fold increase),
gonorrhea among men (2-fold increase), polio among men (2.5-fold increase),
endocrine gland disorders among women (3.3-fold increase), and cimetidine and
histamine H2-receptor antagonists, which are medications for
Contact: Abby Sinnott
University of California - San Francisco