Treatment concepts of acute promyelocytic leukemia

In the past, acute promyelocytic leukemia (APL) was associated with a high risk of early mortality resulting from severe coagulopathy, frequently inducing fatal cerebral hemorrhage. With the introduction of the differentiating agent all-trans retinioc acid (ATRA) APL has changed to the best curable subtype of acute myeloid leukemia (AML). With ATRA and chemotherapy approximately 70-80% of patients with newly diagnosed APL achieve long-term remission and are probably cured. PML/RARalpha, the molecular fusion transcript of the specific translocation t(15;17) represents not only the target for ATRA but also permits a precise diagnosis and provides a marker for the identification of minimal residual or recurrent disease (MRD). During the last decade, substantial progress has been made with regard to the recognition of prognostic factors and the optimization of the combination of ATRA and chemotherapy. Remaining questions are the role of arsenic and of ara-C in first line therapy of APL as well as the indication of maintenance therapy in the individual patient. Several treatment options exist for patients with APL who have relapsed after ATRA and chemotherapy. Approximately 50% of the patients in first relapse can achieve long-lasting second remission and might be cured with salvage regimens. Currently, arsenic compounds and transplantation procedures seem to be the most promising options in relapsed disease. The role of CD33 antibodies has to be determined in future studies. Refining the molecular monitoring of MRD by quantitative RT-PCR, better elucidation of the biologic mechanisms, and the identification of prognostic factors might be helpful to make further progress in the treatment of APL.