Epidemiology of Hairy Cell Leukemia in Los Angeles County

Abstract

The descriptive epidemiological characteristics of hairy cell leukemia (HCL), a rare chronic lymphoproliferative disorder, were examined by using incidence data collected from 1972 to 1987 by the Cancer Surveillance Program, the population-based cancer registry for Los Angeles County. During the study period, 208 incident cases of histologically confirmed HCL were diagnosed. HCL comprised 2% of all leukemias diagnosed in Los Angeles County during the study period. HCL risk was concentrated in white males; there were few black and Asian patients for analysis. Overall, the age-adjusted incidence rate of HCL for men (2.9/million population) was 4.8 times greater than that for women (0.6/million population). Using data from all cancer patients diagnosed during the study period, Jewish men had significantly greater risk of HCL than Protestant men (odds ratio (OR) = 3.0, P < 0.0001); there was no significant variation in risk of HCL by religion for women. For men, the OR was significantly elevated for professional and technical workers (OR = 2.1, P = 0.001); within this category of occupations, risk was significantly elevated for engineers (OR = 4.0, P = 0.0008). HCL patients were more than twice as likely to have multiple primary cancer diagnoses as other cancer patients. Since the majority of the other primary cancer diagnoses occurred prior to (>1 year) or concurrent with (≤1 year) the HCL diagnosis, this greater frequency of multiple primaries in HCL patients may be due to impaired immune function.