PML/RAR alpha transcripts monitored by polymerase chain reaction in acute promyelocytic leukemia during complete remission, relapse and after bone marrow transplantation

The translocation t(15;17)(q24;q21), unique to acute promyelocytic leukemia (APL), gives rise to PML/RARα fusion transcripts detected by the sensitive reverse transcriptase-polymerase chain reaction (PCR) technique. PCR may help in the diagnosis and in monitoring minimal residual disease. Reversion of PCR to negative is obtained by chemotherapy (CT) alone or in combination with all-trans retinoic acid (ATRA). Here we show a serial PCR study of 10 APL cases. Five cases were studied at the time of diagnosis, and all were PCR positive for the rearranged transcripts (three bcr1 type, two bcr3 type). Seven cases in complete remission (CR) after one cycle of induction CT were persistently PCR negative, one case in CR after ATRA rescue was persistently PCR positive (bcr1 type), one patient (bcr3 type) relapsed 15 months after the PCR-negative CR and one patient died early. Seven patients underwent bone marrow transplantation (BMT) (five allogeneic, two autologous). One of them died early after take of the allogeneic BMT, the other six cases studied by serial PCR were persistently negative. At a median follow-up of 31 months (range 9-39), none of these six cases had relapsed. PCR data characterize the CR at the molecular level and evaluate the efficacy of different treatments, including BMT. The data may help to define a standardized schedule for PCR follow-up, and are also potentially useful to establish the time required before judging patients with persistently negative PCR to be cured. BMT as post-induction treatment in first CR is also discussed.