Reclassification of leukemia among A-bomb survivors in Nagasaki using French-American-British (FAB) classification for acute leukemia.

The concordance rate for diagnoses of atomic bomb-related cases of leukemia in Nagasaki was determined using the French-American-British (FAB) classification for acute leukemias and myelodysplastic syndromes (MDS). Two Radiation Effects Research Foundation (RERF) hematologists and one of the members (JMB) of the FAB cooperative group reviewed independently the peripheral blood and/or bone marrow smears from 193 people with leukemia or a related disorder. There was 85% agreement in the identification of types and subtypes of acute leukemia. There was almost complete agreement for the diagnoses of non-FAB disorders (chronic myeloid leukemia (CML), adult T-cell leukemia (ATL) and others) resulting in overall concordance of 88.2%. The present study suggests that the previously established leukemia types for about a quarter of the cases of acute leukemia and related disorders except CML should be changed. Considerable numbers of cases of ATL and MDS were involved in this series. The frequency of the former disease was not high in the high-dose irradiated group, but that of the latter was considerably high. All subtypes of AML except M3 and M6 were present in the high-dose group. The striking difference in CML incidence between Nagasaki and Hiroshima may continue to be a problem in relation to biological response to radiation exposure.