Chromosomal analysis of myelodysplastic syndromes among atomic bomb survivors in Nagasaki

The myelodysplastic syndromes (MDS) are clonal haematopoietic disorders that develop de novo and also secondary to chemotherapy and/or radiation therapy. We previously demonstrated that the risk of MDS is increased among atomic bomb survivors with significant correlation to radiation dose; however, the clinical characteristics of these survivors have not been well analysed. In this study, we investigated chromosomal abnormalities of MDS among survivors. The frequency of abnormal karyotypes was significantly higher, with more very poor risk karyotypes, according to the revised International Prognostic Scoring System, among those exposed close to the hypocentre compared with unexposed cases. However, abnormal karyotype frequency did not reflect the prognosis of exposed cases with respect to distance from the hypocentre. In addition, there was no difference in prognosis between exposed and unexposed cases. Among proximally exposed cases (<1·5 km from the hypocentre), chromosomal translocations and inversions were more frequent, and the frequency of structural alterations in chromosomes 3, 8, and 11 was significantly increased compared with unexposed cases. These results suggest that chromosomal alterations in MDS among survivors have different features compared with those in de novo or therapy-related MDS. Detailed molecular study is warranted.