Detection of Minimal Residual Disease in Acute Lymphoblastic Leukemia Patients by Polymerase Chain Reactions

Significant progress has been achieved in the treatment of acute lymphoblastic leukemia (ALL) by the introduction of modern chemotherapeutic strategies [1]. However, disease relapse following successful remission induction still poses a major clinical challenge. The quantity and kinetic behavior of residual leukemic cells remains largely enigmatic due to the limitation of most currently available techniques to identify less than 1%–5% neoplastic cells in the population being examined [2]. The use of double-color immunofluorescence has markedly improved the sensitivity with which persisting disease can be detected in distinct leukemias characterized by phenotypic features that are extremely rare or absent on normal hematopoietic counterparts [3]. More recently the development of polymerase chain reaction (PCR) strategies has opened a new era in the analysis of minimal residual disease by allowing the identification of neoplastic cells at a 10−4 to 10−6 level [4]. In the following we will summarize our experience with the application of PCR techniques in monitoring ALL patients during the course of the disease.