Departments of 1 Medical Oncology, 2 Pathology and 3 Cancer Control Strategy, British Columbia Cancer Agency and the University of British Columbia, Vancouver, BC, Canada; Departments of 4 Medicine and 5 Pathology, University of Hong Kong, Queen Mary Hospital; 6 Hong Kong Cancer Registry, Queen Elizabeth Hospital, Hong Kong, Peoples Republic of China
Received 30 August 2003; revised 30 October 2003; accepted 22 December 2003
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ABSTRACT |
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Compared with the West, Hodgkins lymphoma in Oriental countries is characterized by a lower incidence rate and a higher proportion of mixed cellularity histology. Both environmental and genetic factors may be involved.
Patients and methods:
The incidence and pattern of pathology of Hodgkins lymphoma in the migrant Chinese population (0.4 million) in British Columbia (population 3.2 million) were studied. From a computerized database, all Hodgkins lymphoma cases diagnosed in British Columbia from 1970 to 1997 were identified. Chinese descent was determined using patient surname by standard methodology and verified from the treatment record or by patient interview. The corresponding figures from the Chinese population in Hong Kong were used for comparison. For incidence rates, the age-specific incidence of Hodgkins lymphoma in Hong Kong was obtained from the government cancer registry. For comparison of histology subtypes, 200 Hodgkins lymphoma records from a Hong Kong regional referral center for the same time period were reviewed. Crude and age-standardized incidence rates were calculated by 5-year intervals in terms of age and calendar year, and relative rates were compared between the three populations.
Results:
From 1970 to 1997, Hodgkins lymphoma was diagnosed in 34 Chinese patients in BC, with 24 cases diagnosed from 1970 to1994. Thus, the crude and age-adjusted incidence rates from 1970 to 1994 were 0.91 and 1.14 per 100 000 per year in the British Columbia Chinese migrant population. Within the same period, 1862 cases of Hodgkins lymphoma were diagnosed in British Columbia, giving a provincial background crude and age-adjusted incidence rates of 5.2 and 4.87 per 100 000 per year. The number of cases in the Hong Kong Chinese population (19701994) was 404, giving crude and age-adjusted incidence rates of 0.32 and 0.31 per 100 000 per year, respectively. Corrected for age and calendar year trends, the observed 25-year incidence of Hodgkins lymphoma in British Columbia Chinese was significantly lower than expected from the British Columbia background population [24 observed versus 71 expected cases; standardized incidence ratio (SIR) = 0.34; 90% confidence interval (CI) 0.240.48; P <0.0001]. On the other hand, it is higher than that expected by extrapolating from the Hong Kong Chinese population (24 observed versus 8.5 expected cases; SIR = 2.81; 90% CI 1.943.95; P <0.0001). The difference is mainly accounted for by young patients with nodular sclerosis type disease in the migrant population.
Conclusions:
Although any conclusion about the impact of migration on Hodgkins lymphoma incidence and types in the Chinese population must be considered tentative due to the small number of observed cases and confounding variables such as age, changing diagnostic standards and secular trends in Hodgkins lymphoma rates, our data demonstrate a tendency for the Chinese population of British Columbia to take on a Western pattern of Hodgkins lymphoma. This observation provides additional evidence that both genetic and environmental influences play a role in the pathogenesis of this lymphoma, and that environmental factors can exert their influence over a relatively short period of time.
Key words: Chinese, Hodgkins lymphoma, incidence, migration
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Introduction |
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Patients and methods |
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The age distributions of the British Columbia background population and the Chinese subpopulation of British Columbia were obtained from Statistics Canada from 5-yearly census figures. The Hong Kong Chinese population was taken as a reference population for the incidence of Hodgkins lymphoma in individuals of Chinese ethnicity. Hodgkins lymphoma incidence figures were obtained from the Hong Kong Tumor Registry, which has a catchment accuracy of 90%. Population statistics for Hong Kong were obtained from the Census Department of the Government of the Special Administrative Region of Hong Kong, China. Age-adjusted incidence rates were calculated for the British Columbia, Hong Kong and Chinese migrant populations using World Health Organization world age-standardized rates [13]. The Queen Mary Hospital (QMH) is the major referral center for Hodgkins lymphoma in Hong Kong. Histology records of all Hodgkins lymphoma cases from BCCA (n = 2013) and QMH (n = 200) from 1970 to 1997 were reviewed to provide background information on histology distribution.
Standardized incidence ratios (SIRs) were used to compare the Hodgkins lymphoma incidence in the British Columbia Chinese population with that of the British Columbia and Hong Kong general populations. SIRs of Hodgkins lymphoma were calculated by 5-year age groups and 5-year calendar periods. Since census figures in Hong Kong and British Columbia and the incidence of Hodgkins lymphoma in the Hong Kong population have only been published for the years 19701994, only this period was used for statistical calculations. Tests of significance for the differences in the SIRs were calculated assuming the observed number of cases followed a Poisson distribution, with the mean given by the expected number of cases of Hodgkins lymphoma based on British Columbia and Hong Kong population rates [14]. One-sided t-test and 90% confidence intervals (CIs) corresponding to a 5% significance level were used.
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Results |
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Discussion |
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For diseases with significant environmental risk factors, there is a tendency for migrant populations to take on the disease pattern of the country in which they settle. For malignant diseases, such observations are well documented in breast [9] and colon cancer [8] in Asian migrants to the United States. There have been very few studies on the effect of migration on the incidence of Hodgkins lymphoma. Studies of Hodgkins lymphoma in Asian immigrants to Los Angeles and Hawaii in the United States quoted similar rates to their parent population in China, Japan and the Philippines [1, 3, 22]. However, a study of Indian migrants to the UK showed a two-fold increase in risk [23]. Our study in Chinese migrants to British Columbia showed a three-fold increase in crude incidence from 0.32 to 0.91 cases per 100 000 per year. These data must be interpreted cautiously, since the incidence of Hodgkins lymphoma varies with age and calendar year [1]. In most Western countries, the age-related incidence of Hodgkins lymphoma follows a bimodal pattern, whereas the early peak is less obvious in Asians, mainly due to the lower number of young nodular sclerosing cases [2, 3, 16]. In both the Hong Kong and British Columbia populations, the age-adjusted rates of Hodgkins lymphoma have not changed significantly over the 25 years. Small rate increases in young adults and decreases in older adults have been observed (Figures 1 and 3). These were statistically controlled for by SIR calculations. Allowing for such variations and sample size, it appears that the increase in rate of Hodgkins lymphoma seen in the migrant Chinese British Columbia population is genuine.
The lower median age of disease in the migrant group and the higher proportion of nodular sclerosing disease seem to follow the Western trends. It is unlikely that this is due to variations in diagnostic standards, since morphological diagnosis of nodular sclerosing and mixed cellularity Hodgkins lymphoma in tertiary centers usually show high levels of concordance [24, 25]. Unfortunately, the small number of index cases precludes a meaningful statistical analysis of the shift in incidence in terms of histology subtypes, and between first- and second-generation migrants. Any conclusion about the impact of migration on Hodgkins lymphoma incidence and types in the Chinese population must be considered tentative due to the small number of observed cases, differences in case ascertainment and reporting, inaccurate population estimation, and confounding variables such as age, changing diagnostic standards and secular trends in Hodgkins lymphoma rates. To study such issues further, a larger study cohort would be required, with the collaboration of several cancer registries. Pending qualification from such larger studies, our data are consistent with the hypothesis that Chinese migrants to a Western country such as Canada rapidly acquire a higher risk of Hodgkins lymphoma and a tendency to develop the same histological subtypes of disease seen in the host country. This observation provides additional evidence that both genetic and environmental influences play a role in the pathogenesis of this lymphoma and that such environmental factors can exert their influence in a relatively short period of time. If verified, such observations strengthen the evidence for environmental factors playing a major role in Hodgkins lymphoma causation.
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FOOTNOTES |
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REFERENCES |
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2. Liang R, Yau C, Muckaden M et al. Hodgkins disease in Asia. In Mauch P, Armitage JO, Diehl V et al. (eds): Hodgkins Disease. Philadelphia, PA: Liipincott Rave Press, 1999.
3. Parkin D, Muir C, Whelan S. Cancer in Five Continents. Volume VI, IARC Scientific Publications No. 120. Lyon, France: IARC, 1992.
4. Diehl V, Tesch H. Hodgkins diseaseenvironmental or genetic? N Engl J Med 1995; 332: 461462.
5. Cozen W, Katz J, Mack TM. Risk patterns of Hodgkins disease in Los Angeles vary by cell type. Cancer Epidemiol Biomarkers Prev 1992; 1: 261268.[Abstract]
6. Glaser SL. Black-white differences in Hodgkins disease incidence in the United States by age, sex, histology subtype and time. Int J Epidemiol 1991; 20: 6875.[Abstract]
7. Dunn JE. Cancer epidemiology in populations of the United Stateswith emphasis on Hawaii and Californiaand Japan. Cancer Res 1975; 35: 32403245.[Abstract]
8. Stemmermann GN, Nomura AM, Heilbrun LK et al. Serum cholesterol and colon cancer incidence in Hawaiian Japanese men. J Natl Cancer Inst 1981; 67: 11791182.[ISI][Medline]
9. Ziegler RG, Hoover RN, Nomura AM et al. Relative weight, weight change, height, and breast cancer risk in AsianAmerican women. J Natl Cancer Inst 1996; 88: 650660.
10. Muir CS, Nectoux J, Staszewski J. The epidemiology of prostatic cancer. Geographical distribution and time-trends. Acta Oncol 1991; 30: 133140.[ISI][Medline]
11. Choi B, Hanley A, Holowaty E, Dale D. Use of surnames to identify individuals of Chinese ancestry. Am J Epidemiol 1993; 138: 723734.[Abstract]
12. Hage B, Oliver R, Powles J, Wahlqvist M. Telephone directory listings of presumptive Chinese surnames: an appropriate sampling frame for a dispersed population with characteristic surnames. Epidemiology 1990; 1: 405408.[Medline]
13. Bray F, Guilloux A, Sankila R, Parkin DM. Practical implications of imposing a new world standard population. Cancer Causes Control 2002; 13: 175182.[CrossRef][ISI][Medline]
14. Breslow N, Day N. The Design and Analysis of Cohort Studies. Lyon, France: IARC, 1987.
15. Liang R, Choi P, Todd D et al. Hodgkins disease in Hong Kong Chinese. Hematol Oncol 1989; 7: 395403.[ISI][Medline]
16. Tomita Y, Ohsawa M, Kanno H et al. EpsteinBarr virus in Hodgkins disease patients in Japan. Cancer 1996; 77: 186192.[CrossRef][ISI][Medline]
17. Huh J, Park C, Juhng S et al. A pathologic study of Hodgkins disease in Korea and its association with EpsteinBarr virus infection. Cancer 1996; 77: 949955.[CrossRef][ISI][Medline]
18. Glaser SL, Lin RJ, Stewart SL et al. EpsteinBarr virus-associated Hodgkins disease: epidemiologic characteristics in international data. Int J Cancer 1997; 70: 375382.[CrossRef][ISI][Medline]
19. Monterroso V, Zhou Y, Koo S et al. Hodgkins disease in Costa Rica: a report of 40 cases analyzed for EpsteinBarr virus. Am J Clin Pathol 1998; 109: 618624.[ISI][Medline]
20. Chan JK, Yip TT, Tsang WY et al. Detection of EpsteinBarr virus in Hodgkins disease occurring in an Oriental population. Hum Pathol 1995; 26: 314318.[ISI][Medline]
21. Liu SM, Chow KC, Chiu CF, Tzeng CH. Expression of EpsteinBarr virus in patients with Hodgkins disease in Taiwan. Cancer 1998; 83: 367371.[CrossRef][ISI][Medline]
22. Yanagihara ET, Blaisdell RK, Hayashi T, Lukes RJ. Malignant lymphoma in Hawaii-Japanese: a retrospective morphologic survey. Hematol Oncol 1989; 7: 219232.[ISI][Medline]
23. Varghese C, Barrett JH, Johnston C et al. High risk of lymphomas in children of Asian origin: ethnicity or confounding by socioeconomic status? Br J Cancer 1996; 74: 15031505.[ISI][Medline]
24. Georgii A, Fischer R, Hubner K et al. Classification of Hodgkins disease biopsies by a panel of four histopathologists. Report of 1140 patients from the German National Trial. Leuk Lymphoma 1993; 9: 365370.[ISI][Medline]
25. Glaser SL, Swartz WG. Time trends in Hodgkins disease incidence. The role of diagnostic accuracy. Cancer 1990; 66: 21962204.[ISI][Medline]