New approaches to acute lymphoblastic leukemia in adults: where do we go?

The optimization of conventional treatment approaches, such as chemotherapy, stem cell transplantation (SCT), and supportive care, and the exploration of new approaches will hopefully further improve the outcome of adults with acute lymphoblastic leukemia (ALL). Subgroup-adjusted treatment has already greatly improved treatment outcomes in T- and mature B-cell ALL. These approaches should be further refined, for example, in T-ALL with cyclophosphamide and cytarabine, in pro-B ALL with high-dose cytarabine (HdAC), in B-precursor ALL with high-dose methotrexate (HdM) and 6-mercaptopurine (6-MP), and in mature B-ALL with HdM and HdAC. The indications for SCT will be extended to include elderly patients undergoing allogeneic mini-transplants, and tumor eradication will be improved by better conditioning regimens such as radioimmunoconjugates and methods to induce the graft-versus-leukemia (GvL) effect, such as donor leukocyte infusions (DLI) or allogeneic mini-transplants applied after autologous transplants. Molecular therapeutic approaches, for example, those directed against the fusion protein BCR-ABL with ABL-tyrosine kinase inhibitor, are on the way to creating a new avenue for the treatment of ALL. In the future, drug resistance should be exploited as a pretherapeutic test for treatment strategies, but whether multidrug resistance modulation with available drugs will be used in ALL remains open. Evaluation of the pharmacokinetics of cytostatic drugs and the pharmacogenomics of cytostatic agents in adult ALL may contribute to the development of individualized treatment strategies with higher efficacy and lower toxicity. Minimal residual disease (MRD) evaluation is attractive in adult ALL, because it can be determined in a very high percentage of patients. It has been shown to be predictive for relapse and might be of benefit for redefinition of complete remission (CR), for determination of the efficacy of single treatment elements, and for treatment tailoring during the course of disease. New treatment approaches include also several forms of immunotherapy for B- as well as T-lineage ALL; after the demonstration that such approaches are also effective in ALL, their optimal place in the treatment strategy for adult ALL can be determined.