Risks among siblings and twins for childhood acute lymphoid leukaemia: results from the Swedish Family-Cancer Database (original) (raw)

Leukemia volume 16, pages 297–298 (2002)Cite this article

ALL is the most common leukaemia in childhood and together with nervous system tumours it is the main type of childhood neoplasm.1 Despite numerous etiological studies, the established risk factors of childhood ALL are few and they account for a small fraction of all cases. According to Little,1 ‘factors generally accepted as associated’ with leukaemia in childhood include ataxia telangiectasia, Fanconi's anaemia, neurofibromatosis 1, certain types of hereditary immunodeficiency, Down syndrome and, according to earlier studies, intrauterine exposure to X-rays. Remarkably, all but the last factor are genetic conditions. Malignant ALL cells contain diverse clonally expanded gene fusions that are thought to be the initiating event in leukaemogeneis.2 Infections or the ensuing aberrant immune responses are other risk factors for ALL, which, together with other environmental events, precipitate the disease.2,3 Data on twin studies have been controversial or difficult to interpret due to possible selection.1 In a recent Nordic twin study on 90000 twins, only two pairs each of monozygotic and dizygotic twins concordant for any type of leukaemia at any age were recorded.4 Parental leukaemia has not been associated with childhood ALL but leukaemia in a sibling has been a risk factor for leukaemia in other siblings.1

Because of lack of population-based data on familial risk factors of childhood ALL, we examine here these relationships using the nation-wide Swedish Family-Cancer Database including all Swedes, ‘offspring’ born since 1932 with their parents recorded at birth. The parental population can assume any age in the Database but ALL in the offspring population was considered between ages 0 and 19 years. The Database has been updated in 2001 to include over 10 million individuals and over 1 million malignancies notified to the Swedish Cancer Registry between 1958 and 1998. In addition to familial relationships and neoplasms, the Database contains information on residential area and socio-economic status. Familial risks were calculated for offspring separately for families where only a parent or only a sibling was affected with any malignancy. There were no families where a parent and two siblings were affected by ALL. Standardized incidence ratios (SIRs) were calculated by dividing the observed numbers (O) of cases by the expected (E) ones, calculated as person-years at risk based on age (5-year age-groups)-, period (5-year periods)-, area of residence (two categories)-, socio-economic status (four categories)- and sex-specific incidence rates for all persons in the Data- base.5 Confidence intervals (95% CI) were calculated assuming a Poisson distribution. 95% CIs for siblings were adjusted for dependence.5

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References

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Acknowledgements

Grant support from The Childhood Cancer Fund.

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  1. Department of Biosciences at Novum, Karolinska Institute, Huddinge, 141 57, Sweden
    K Hemminki & Y Jiang

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  1. K Hemminki
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  2. Y Jiang
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Hemminki, K., Jiang, Y. Risks among siblings and twins for childhood acute lymphoid leukaemia: results from the Swedish Family-Cancer Database.Leukemia 16, 297–298 (2002). https://doi.org/10.1038/sj.leu.2402351

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