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Richard Lane
The Lancet
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The association between exposure to cosmic radiation and leukaemia among aircrew is strengthened by genetic research published in this weekís issue of THE LANCET.

Previous research by Maryanne Gundestrup and colleagues from the Institute of Cancer Epidemiology, Copenhagen, Denmark (Radiation-induced acute myeloid leukaemia and other cancers in commercial jet cockpit crew: a population-based cohort study. Lancet 1999; 354: 2029-31) suggested an association between cosmic radiation exposure at high altitude and an increased risk of myeloid leukaemia among aircrew. A year later, the same group of investigators suggest that exposure to cosmic radiation may cause changes to chromosome 7, which is associated with the development of myeloid leukaemia.

The investigators studied the karyotypes (chromosome arrangements) of seven aircrew treated for myelodysplasia (bone-marrow abnormalities, which may be a precursor of myeloid leukaemia) or acute myeloid leukaemia between 1987 and 1999. They compared them with the karyotypes of 19 cases of myelodysplasia or acute myeloid leukaemia after radiotherapy between 1980 and 1998. The karyotypes of these groups were compared with the range of chromosome aberrations found in 761 patients with myelodysplasia or acute myeloid leukaemia studied in Lund, Sweden.

Deletion or loss of chromosome 7 was found in four of seven aircrew with myelodysplasia or acute myeloid leukaemia, and in eight of 19 patients with the disorders after radiotherapy alone. Both the aircrew and radiotherapy groups showed an excess of chromosome abnormality compared with the Swedish data of patients with myelodysplasia or myeloid leukaemia.

Maryanne Gundestrup comments: ìOur results indicate that deletions or loss of the long arm of chromosome 7 in myelodysplasia and acute myeloid leukaemia could be an indicator of previous exposure to ionising radiation. Larger studies will be needed to confirm a link between myelodysplasia and acute myeloid leukaemia in aircrew and exposure to cosmic radiationî.

Contact: Dr Maryanne Gundestrup, National Clinic of Aviation Medicine, University Hospital Copenhagen and Institute of Cancer Epidemiology, Danish Cancer Society, Copenhagen, Tagensvej 20, DK 2200 N Copenhagen, Denmark; T) +45 3545 7522; F) +45 3545 7627; E)