Clonal Evolution in Relapse of Acute Lymphoblastic Leukemia

Abstract

Sequential cytogenetic studies were performed in 5 patients with acute lymphocytic leukemia (ALL) who achieved remission and later had a relapse. One patient had tetraploidy in their leukemic cells at diagnosis as well as in relapse, in whom detailed studies were not possible. The other 4 patients showed 6 clonal evolutions in total. Three evolutions showed clones derived from the original ones seen at diagnosis, and another a clone which was entirely different from the original one. Another one was progression from diploidy to pesudodiploidy. In the remaining one, there was a shift in the modal chromosome number, but the exact nature of the evolution was not determined because of the insufticient analysis at diagnosis.
The modal chromosome number had increased in one, decreased in two and unchanged in the others. Partial trisomy of chromosome 1 appeared in two patients, and karyotypic instability in one. Remission was not achieved after the discovery of the clonal evolution, and the median survival for the 4 patients after the evolution was only 3.3 months. Clonal evolution appears to be an unfavorable prognostic sign in ALL as it is in chronic myeloctic leukemia (CML).