Acute leukemias in adults: an overview of recent strategies

In 1989, 65%-75% of previously untreated adults with ALL or AML may be expected to enter complete remission. Approximately 40% of these completely responding patients, whether they are treated with intensive chemotherapy, intensive chemotherapy followed by autologous bone marrow transplantation, or allogeneic bone marrow transplantation, remain disease-free after 3 years of follow-up. As such, the likelihood for cure for adults with acute leukemia is approximately 25%-30%. At the present time, no new chemotherapeutic agents of significant importance are on the horizon. Furthermore, it seems doubtful that the mere juggling of drug doses will have any measurable effect on treatment outcome. The use of hematopoietic growth factors, either to allow added tolerance of intensive therapy or to synchronize leukemic cells kinetically, is now under study. Perhaps the most promising area of present investigations deals with immune manipulation. The administration of immunotoxins (a drug or a cell poison chemically linked to a leukemia-related monoclonal antibody) has been associated with promising results in eradicating minimal residual disease in animal model systems. Similarly, attempts at harnessing the graft-versus-leukemia effect without the eligibility restrictions and toxicities associated with the allograft procedure, through the use of lymphokines as enhancers of natural killer cell activity, have also proven to be effective in pre-clinical trials. With the availability of hematopoietic growth factors, immunotoxins, and lymphokines, clinical research in acute leukemia in the future will no longer focus on cytotoxic drugs alone but rather on how the addition of biological agents can prolong the duration of complete remission and increase the potential for cure.