[Prognostic significance of eosinophilia in children with acute myeloid leukemia in the studies AML-BFM-78 and -83].

Initial eosinophilia (greater than or equal to 3%) in the bone marrow was found in 73 out of 269 (27%) patients studied in AML studies BFM-78 and -83. It was predominantly seen in children with FAB types M2 (44%) and M4 (41%). Atypical eosinophils were mostly found in FAB type M4 (20/28 = 71%). Cytogenetic studies in eight children with FAB M4 and eosinophilia showed normal karyotypes in four patients, inversion 16 in one and other aberrations in three children. Study AML-BFM-78 did not demonstrate any differences in prognosis between patients with and without eosinophilia (event-free survival = EFS after 5 years 37%, SD 8%, vs. 38%, SD 6%). In study AML-BFM-83, however, a clear increase in EFS was seen in children with eosinophilia (EFS 72%, SD 8%, vs. 43%, SD 5%, p = 0.001). This improvement of prognosis mainly concerns patients with FAB M4 and eosinophilia (EFS 81%, SD 10%, vs. 23%, SD 11%, p = 0.006). None of the 12 children in study AML-BFM-83 with FAB M4 and atypical eosinophils has suffered a relapse, two patients belong to the early death group. Multivariate analysis shows only eosinophilia as a favorable prognostic factor in FAB type M4. According to these results FAB type M 4 with eosinophilia is a favorable prognostic parameter in children treated according to the therapy protocol of study AML-BFM-83.