Remaining problems in the staging and treatment of childhood lymphoblastic leukemia.

During the past decade, advances in the treatment of childhood acute lymphoblastic leukemia (ALL) have continued. Progress is largely due to improved disease-free survival of poor-prognosis subgroups, improved sanctuary therapy, shortening of therapy duration, and salvage of relapsed patients by use of better chemotherapy regimens and bone marrow transplantation. Nonetheless, more children continue to die of ALL than of any other childhood cancer. This article reviews the progress and indicates remaining problems in the staging and treatment of ALL. Remaining problems include a lack of standardization between staging systems, variable application and interpretation of multivariate analysis, and occurrence of epiphenomenon. Also, to have statistical validity, clinical studies require numbers of patients larger than have been the case as results of treatment improve. Confusing also is the biological interface between ALL, non-Hodgkin's lymphoma, and the myeloid leukemias; the lack of reliable in vitro tests of chemosensitivity and chemoresistance; and the inability to quantitate residual leukemia after remission induction or to detect drug-resistant clones of cells before they are clinically manifest. Delivery of optimum therapy and supportive care to all children with ALL remains an elusive goal.