Chronic lymphocytic leukaemia and small lymphocytic lymphoma: overview of the descriptive epidemiology.

The 2001 World Health Organization classification scheme considers B-cell chronic lymphocytic leukaemia (CLL) and small lymphocytic lymphoma (SLL) in an aggregate category (CLL/SLL) because of shared clinicopathological features. We have estimated age-adjusted incidence rates (IRs) of CLL and SLL in the population-based Surveillance, Epidemiology and End Results Program in the United States to analyse patterns of CLL and SLL separately and jointly. Age-standardized to the 2000 US population, overall IRs were 3·83 per 100 000 person-years for CLL ( n = 15 676) and 1·31 for SLL ( n = 5382) during 1993–2004. Incidence of the combined entity, CLL/SLL, was 90% higher among males compared to females, and the male:female IR ratio was significantly higher for CLL (1·98) than for SLL (1·67). CLL/SLL IRs were 25% and 77% lower among Blacks and Asian/Pacific Islanders, respectively, compared to Whites. A significant reporting delay was evident for CLL but not for SLL, so that CLL/SLL temporal trends must be interpreted cautiously. CLL and SLL IRs increased exponentially with age among all gender/race groups, with CLL IRs increasing more steeply with advancing age than SLL. Avenues of future research include assessment of delayed- and under-reporting to cancer registries and exploration of race, gender, and age effects in epidemiological studies. [ABSTRACT FROM AUTHOR]