Reverse transcription polymerase chain reaction for the diagnosis and molecular monitoring of the PML/RAR alpha fusion gene in acute promyelocytic leukemia.

Acute promyelocytic leukemia (APL) is characterized by a specific t(15;17) translocation and a high rate of response to all-trans retinoic acid. The translocation generates a PML/RAR alpha chimeric gene which is transcribed in a fusion PML/RAR alpha mRNA. In this study, by using RT-PCR, we examined 14 APL patients for PML/RAR alpha fusion gene transcripts. Eight patients were studied at diagnosis, 2 at relapse, 1 both at relapse and after reinduction, 1 both at diagnosis and after three cycles of consolidation chemotherapy, and 2 patients were examined for minimal residual disease (MRD) 4 months after completing treatment. A positive result was observed in all 14 cases. Two patients who were in complete hematologic remission had evidence of hematologic relapse soon after the positive test. We conclude that RT-PCR for APL yields important diagnostic and prognostic information for the APL patients.