Lower incidence of plasma cell neoplasm is maintained in migrant Chinese to British Columbia: findings from a 30-year survey.

The etiology of plasma cell myeloma (PCM) is largely unknown. Its incidence varies widely in different ethnic groups. Migrant study may help determine the relative contributions of genetic versus environmental factors to PCM pathogenesis. We performed a retrospective review of the computerized records of all patients diagnosed with PCM between 1975 and 2004 in British Columbia (BC), and identified patients of Chinese ethnicity. This was compared with PCM incidence in Hong Kong (HK) Chinese. Age distributions of HK, BC and BC Chinese populations were obtained from the census departments to calculate world age-standardized rates (WASRs). The WASR of PCM over the 30-year period in BC Chinese was 1.64/100 000 person-years (95% confidence interval [CI] 1.37-1.93). This was similar to the WASR observed in HK (1.78, 95% CI 1.73-1.83), with a standardized incidence ratio (SIR) of 0.91 (95% CI 0.74-1.10). The rate was much lower than that in the BC non-Chinese background population (WASR 3.59, 95% CI 3.50-3.68; SIR 0.46, 95% CI 0.38-0.56). The lower rates in BC Chinese were maintained across all years, both genders and in all age groups above 45 years. Our observations suggest a strong genetic component as the cause of differences in the ethnic predisposition to PCM.