Karyotypic changes from initial diagnosis to relapse in childhood acute leukemia.

Cytogenetic study was performed at both diagnosis and relapse in 31 children with acute leukemia who had initially abnormal karyotypes, 21 with acute lymphocytic leukemia (ALL) and 10 with acute nonlymphocytic leukemia (ANLL). Seventy percent of the patients showed karyotypic changes between diagnosis and relapse. The ALL patients showed karyotypic changes more often than the ANLL patients (76 vs. 40%)(chi-square test, p less than 0.05). All the initially abnormal patients with karyotypic changes exhibited structural changes, most frequently chromosome 1 abnormalities, especially in ANLL, and 6q-, 7p-, 9p- in ALL. Half of the patients, with structural karyotypic change had two or more clonally related cell lines at relapse. On the other hand, only 20% of the patients with karyotypic changes showed numerical changes. All but one of the initially abnormal patients showed karyotypic changes involving the original cytogenetically abnormal clone. Our study demonstrated that sequential cytogenetic studies may provide a better understanding of the nature of leukemia relapse.