Detection of minimal residual disease in a patient with acute promyelocytic leukemia by RT-PCR: necessity of chemotherapy following ATRA therapy.

The PML/RAR alpha fusion gene resulting from the t (15;17) translocation is a specific marker for acute promyelocytic leukemia (APL). We examined bone marrow cells by reverse transcriptase-polymerase chain reaction (RT-PCR) to detect residual PML/RAR alpha mRNA-containing cells following treatment with all-trans retinoic acid (ATRA) and cytotoxic chemotherapy in a patient with APL. This RT-PCR assay can detect one leukemic cell in 10(2) normal cells in vitro. We show that PML/RAR alpha mRNA was still detectable despite clinical remission following ATRA treatment, but undetectable following consolidation with chemotherapy. These data show that this technique is useful for the identification of minimal residual disease in patients with APL and that cytotoxic chemotherapy following ATRA therapy is required for the elimination of APL cells.