Objective: To evaluate the value of real time quantitative RT-PCR (Q-PCR) for monitoring AML1-ETO mRNA levels in AML1-ETO(+) acute myeloid leukemia (AML) patients following allogeneic hematopoietic stem cell transplantation (allo-HSCT).
Methods: Quantification of AML1-ETO(+) mRNA was performed serially on bone marrow samples from 17 patients with AML1-ETO(+) AML after HSCT. Q-PCR used the TagMan probe system. The AML1-ETO mRNA level was normalized by control gene abl. Cytogenetic response was evaluated by fluorescent in situ hybridization (FISH).
Results: The reproducible sensitivity of Q-PCR was 5 copies. Out of 16 patients who achieved sustained complete cytogenetic response (CCyR), one each died of graft-versus-host disease and infection. The median AML1-ETO mRNA levels in the rest of 14 CCyR patients were 0 (0 - 0.740), 0.026 (0 - 2.900), 0.039 (0 - 3.300) at +1, +2, +3 month post allo-HSCT, respectively and in 5 CCyR patients beyond 1 year following allo-HSCT (median follow-up 685 days) was 0.078 (0.003 - 0.120). The AML1-ETO mRNA levels in one relapsed patient were 0, 9.8 and 5.6 at +1, +2 and +3 month post allo-HSCT, respectively and hematological relapse occurred at +110 day, when the AML1-ETO mRNA levels increased dramatically from 5.600 to 390.000.
Conclusions: Q-PCR is a sensitive technique in monitoring AML1-ETO(+) AML patients post allo-HSCT. Persistence of a low level within one year after allo-HSCT does not mean at risk of relapse. It is necessary to dynamic monitoring AML1-ETO mRNA after remission in t(8;21) AML patients.