Preservation of lower incidence of chronic lymphocytic leukemia in Chinese residents in British Columbia: a 26-year survey from 1983 to 2008.

The incidence of chronic lymphocytic leukemia (CLL) in the Asian population is up to 10 times lower than that in Caucasians. Studies on CLL in Asian residents in North America may help to determine the relative genetic and environmental causes of such a difference. Computerized records of CLL incidence from the combined British Columbia (BC) databases (n = 2736) and the Hong Kong Cancer Registry (HKCR, n = 572) were traced. Ethnic Chinese cases of CLL in BC were identified (n = 35). The world age standardized rates (WASRs) of CLL (per 100 000) were calculated in BC (1.71), HK (0.28) and BC Chinese (0.4), respectively. Using standard incidence ratios (SIRs), the observed BC Chinese case number was comparable to the figure projected from HK rates (SIR 1.3, p = 0.1) but significantly lower than the figure following BC rates (SIR 0.22, p < 0.0001). The difference was maintained over both genders, in all age groups and through the years. Our data over three decades suggest that genetic factors outplay environmental factors to give lower CLL rates in Chinese.