Epidemiology and ethnic aspects of B cell chronic lymphocytic leukemia in Israel

Chronic lymphocytic leukemia (CLL) represents 30% of all leukemias in Caucasians. In East Europe and USA the disease incidence is high while in Asia and Africa CLL is rare. The present study deals with 302 cases of B cell CLL and related disorders; 207 patients originating from Europe and America (Ashkenazi Jews) and 95 descendants from Asia, The Mediterranean or Africa (Sephardic Jews). The patients were recruited during 1975-1996 in a single center covering the Hashfela region - a Southern area of Israel with a current population of 430 000 inhabitants. Incidence of the disease, clinical pattern, biological parameters, prognosis and outcome were investigated and compared in both ethnic groups. The results of this study show a high incidence of CLL in Israel. The mean annual age-adjusted incidence 4.3 per 100 000 person-year is among the highest reported values. Our study confirms previous data on the prevalence of CLL in Ashkenazi compared to Sephardic Jews. The rise in CLL rate in the reviewed period occurred in both populations, mainly in the Sephardic group. The relative risk for Ashkenazies compared to Sephardics decreased from 6.0 in the 1975-1979 period to 2.4 in 1990-1996. A high rate of CLL was found in new immigrants from the former USSR with 26 cases de novo diagnosed and 11 prevalent cases not included in this series among approximately 60 000 new immigrants in the ara over the last 8 years. No differences were found in clinical, laboratory and immunological parameters at the time of diagnosis in the two ethnic groups. The follow-up showed a similar pattern in the disease evolution. A preliminary study of immunoglobulin heavy chain rearrangement performed in 14 patients showed no significant differences in JH hybridization in the early stages of the disease, but more aberrations in advanced CLL in the Ashkenazi group. Our findings suggest that ethnic origin of the patients itself does not affect the biological and clinical behavior of this disease.