BACKGROUND: The overall prognosis of acute myeloid leukemia (AML) patients with mixed-lineage leukemia (MLL) gene-positivity is unfavorable. In this study, we evaluated the expression levels of the MLL gene in AML patients.

MATERIAL AND METHODS: We enrolled 68 MLL gene-positive patients out of 433 newly diagnosed AML patients, and 216 bone marrow samples were collected. Real-time fluorescence quantitative PCR (RQ-PCR) was used to precisely detect the expression levels of the MLL gene.

RESULTS: We divided 41 patients into 2 groups according to the variation of MRD (minimal residual disease) level of the MLL gene. Group 1 (n=22) had a rapid reduction of MRD level to ≤10^–4 in all samples collected in the first 3 chemotherapy cycles, while group 2 (n=19) had MRD levels constantly >10^–4 in all samples collected in the first 3 chemotherapy cycles. Group 1 had a significantly better overall survival (p=0.001) and event-free survival (p=0.001) compared to group 2. Moreover, the patients with >10^–4 MRD level before the start of HSCT (hematopoietic stem cell transplantation) had worse prognosis and higher risk of relapse compared to patients with ≤10^–4 before the start of HSCT.

CONCLUSIONS: We found that a rapid reduction of MRD level to ≤10^–4 appears to be a prerequisite for better overall survival and event-free survival during the treatment of AML. The MRD levels detected by RQ-PCR were basically in line with the clinical outcome and may be of great importance in guiding early allogeneic HSCT (allo-HSCT) treatment.

Keywords: Leukemia, Myeloid, Acute, Myeloid-Lymphoid Leukemia Protein, Neoplasm, Residual, Real-Time Polymerase Chain Reaction