Molecular measurement of minimal residual disease in Philadelphia-positive acute lymphoblastic leukaemia

The Philadelphia chromosome (Ph) is found in approximately 5–25% of acute lymphoblastic leukaemia (ALL) cases and is the harbinger of a poor outcome. Polymerase chain reaction (PCR) assays can detect leukaemia-specific genetic lesions down to a sensitivity approaching one leukaemia cell in a background of a million normal cells. In Ph+ ALL, the unique BCR - ABL translocation is thus a specific target for the detection of minimal residual disease (MRD). After chemotherapy or transplantation the detection of residualBCR - ABL transcripts is associated with a high risk of subsequent relapse. With the advent of novel therapeutics that target the structure and function of BCR - ABL, the detection of MRD may allow for targeted therapy that could abort a potential relapse.