Cytogenetics of myelodysplasia and acute myeloid leukaemia in aircrew and people treated with radiotherapy.

Increased risk of acute myeloid leukaemia has been reported in aircrew, possibly in association with cosmic radiation. We studied the cytogenetics of seven aircrew members who had acute myeloid leukaemia or myelodysplasia and found deletion or loss of chromosome 7 in four. The same abnormality was found in eight of 19 patients with leukaemia after radiotherapy alone. By comparison, only 81 of 761 unselected cases of myelodysplasia or acute myeloid leukaemia had the same cytogenetic abnormalities. Our results support the concept that deletions or loss of the long arm of chromosome 7 in myelodysplasia and acute myeloid leukaemia could indicate previous exposure to ionising radiation.