Clinical and biological features predict relapse hazard in childhood acute lymphoid leukemia

Remarkable progress has been made in understanding the immunobiology, cytogenetic features and potential molecular pathogenetic mechanisms of childhood acute lymphoid leukemias (ALL). Studies of the expression of certain lineage restricted molecules on the surface of or within normal lymphoid cells and their malignant counterparts have been largely responsible for this advance, which has markedly improved the classification of ALL. These studies have disclosed previously unrecognized biologic heterogeneity and have shown that there are several different immunophenotypic subsets of ALL. Some of these subsets differ in their clinical and cytogenetic features, as well as in their responsiveness to modern therapy, underscoring the clinical relevance of such studies. A consideration of all of these features of ALL permits a more accurate assessment of prognosis for children with newly diagnosed disease and has permitted tailoring therapy based on expected relapse hazard. Recent cytogenetic studies have disclosed that clonal abnormalities are present in the blast cells of most children with ALL. Furthermore, such studies have demonstrated increasing numbers of non-random structural anomalies of chromosomes, some of which are specific for certain immunophenotypic species of ALL. Finally, molecular studies of some of these particularly informative cytogenetic anomalies in leukemic cells have suggested that proto-oncogenes are altered and/or activated as a consequence of chromosomal rearrangements.(ABSTRACT TRUNCATED AT 250 WORDS)