Role of minimal residual disease evaluation in leukemia therapy

Automated analysis of acute myeloid leukemia minimal residual disease using a support vector machine

We investigated the ability of support vector machines (SVM) to analyze minimal residual disease (MRD) in flow cytometry data from patients with acute myeloid leukemia (AML) automatically, objectively and standardly. The initial disease data and MRD review data in the form of 159 flow cytometry standard 3.0 files from 36 CD7-positive AML patients in whom MRD was detected more than once were exported. SVM was used for training with setting the initial disease data to 1 as the flag and setting 15 healthy persons to set 0 as the flag. Based on the two training groups, parameters were optimized, and a predictive model was built to analyze MRD data from each patient. The automated analysis results from the SVM model were compared to those obtained through conventional analysis to determine reliability. Automated analysis results based on the model did not differ from and were correlated with results obtained through conventional analysis (correlation coefficient c = 0.986, P > 0.05). Thus the SVM model could potentially be used to analyze flow cytometry-based AML MRD data automatically, objectively, and in a standardized manner.

Autologous stem cell transplantation for adult acute leukemia in 2015: time to rethink? Present status and future prospects

The use of autologous stem cell transplantation (ASCT) as consolidation therapy for adult patients with acute leukemia has declined over time. However, multiple randomized studies in the past have reported lower relapse rates after autologous transplantation compared with chemotherapy and lower non-relapse mortality rates compared with allogeneic transplantation. In addition, quality of life of long-term survivors is better after autologous transplantation than after allogeneic transplantation. Further, recent developments may improve outcomes of autograft recipients. These include the use of IV busulfan and the busulfan+melphalan combination, better detection of minimal residual disease (MRD) with molecular biology techniques, the introduction of targeted therapies and post-transplant maintenance therapy. Therefore, ASCT may nowadays be reconsidered for consolidation in the following patients if and when they reach a MRD-negative status: good- and at least intermediate-1 risk acute myelocytic leukemia in first CR, acute promyelocytic leukemia in second CR, Ph-positive acute lymphocytic leukemia. Conversely, patients with MRD-positive status or high-risk leukemia should not be considered for consolidation with ASCT.

PCR for monitoring of minimal residual disease in hematologic malignancy

Monitoring minimal residual disease (MRD) is useful to evaluate therapeutic response and risk of relapse in patients with hematologic malignancy. Currently available quantitative MRD assays are fluorescence in situ hybridization of chromosomal aberrations; multiparameter flow cytometry of leukemia-associated immunophenotypes; and quantitative polymerase chain reaction (qPCR) analysis of fusion genes, immunoglobulin/T-cell receptor gene rearrangements, genetic alterations, or over-expressed genes. Among the PCR-based markers, genetic alterations are found in acute myelogenous leukemia patients with cytogenetically normal karyotype and can be considered as applicable targets for monitoring of MRD. Screening, confirmation and quantification procedures are important to develop the patient- or tumor-specific MRD assays using the PCR-based markers. Wild-type blocking PCR or coamplification at lower denaturing temperature-PCR is suited for screening of low-abundant genetic alterations, and allele-specific qPCR using primers including mismatched base and locked nucleic acids can quantify not only insertion and duplication of several nucleotides but also single nucleotide mutation in the presence of an excess amount of wild-type nucleotides. In addition to the well-established MRD markers, such as immunoglobulin/T-cell receptor gene rearrangements and fusion genes, utilizing potential MRD markers such as genetic alterations may expand the spectrum of patients in whom MRD can be monitored.