Reverse transcriptase/polymerase chain reaction follow-up and minimal residual disease detection in t(1;19)-positive acute lymphoblastic leukaemia

The t(1;19) is the most frequent recurring chromosomal translocation in childhood acute lymphoblastic leukaemia (ALL). In most cases typical chimaeric E2A-PBX1 transcripts are expressed as a consequence of this rearrangement, allowing the molecular detection of the t(1;19) at the RNA level. This translocation has been associated with a poor clinical outcome, although intensified chemotherapy has been reported to nullify its adverse prognostic impact. We therefore used reverse transcriptase/polymerase chain reaction (RT-PCR) to detect residual leukaemic cells at successive times during treatment and to monitor the response to chemotherapy in six t(1;19)-positive ALL paediatric patients. Five of these patients rapidly achieved molecular remission and no evidence of minimal residual disease (MRD) was found in the remission bone marrows beyond the third month of treatment. One patient still displayed residual leukaemic cells at the end of therapy, although she has been in continuous complete clinical remission (CCR) for 84 months. However, this patient is peculiar in our series in that two different types of chimaeric E2A-PBX1 transcripts were expressed in her leukaemic cells, only one being detectable in remission.