(HealthDay News) — For children with acute myeloid leukemia (AML), minimal residual disease (MRD) activity, as measured using flow cytometry, is a good indicator of treatment response, with morphologic analysis providing limited additional information, according to a study published online Sept. 10 in the Journal of Clinical Oncology.

Hiroto Inaba, M.D., Ph.D., of the St. Jude Children’s Research Hospital in Memphis, Tenn., and colleagues conducted a study using follow-up bone marrow samples from 203 children and adolescents with newly diagnosed AML. The authors sought to determine the effectiveness of using MRD monitoring with flow cytometry, polymerase chain reaction (PCR) amplification of fusion transcripts, or morphology to assess treatment response.

The researchers found that, of the 1,215 samples with <5 percent leukemic myeloblasts by morphology, 8.2 percent were MRD positive based on flow cytometry, while 57.5 percent of the 167 samples with ≥5 percent blasts were MRD negative. Ninety-nine percent of the MRD-negative samples by PCR were also negative by flow cytometry; however, only 9.6 percent of PCR-positive samples were positive using flow cytometry. Most of the discrepancies came from samples containing AML1-ETO and CBFβ-MYH11. MRD by flow cytometry after induction one or two was predictive of high relapse rate and lower event-free survival. In multivariable analysis, MDR flow cytometry was an independent prognostic factor, with prediction not improved by morphologic information or molecular findings.

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“Our study shows that measurements of treatment response by flow cytometry are widely applicable and provide strong prognostic information,” the authors write. “By contrast, the value of morphologic monitoring is limited, and PCR results of AML1-ETO and CBFβ-MYH11 are difficult to interpret.”


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