Background: Minimal residual disease (MRD) is an important prognostic maker in acute lymphoblastic leukemia (ALL). However, few data comparing the measurement of adult ALL MRD using different methods in daily practice are available. We conducted an analysis comparing the importance of flow cytometry (FCM) and real-time quantitative polymerase chain reaction (PCR) in the assessment of MRD in adult ALL.
Patients and methods: Fifty-six consecutive adult patients with both Philadelphia-negative and -positive ALL treated according to an intensive protocol were enrolled in the study. Bone marrow samples were acquired on day 26 and during week 11 of treatment. MRD evaluation was performed using 8-color FCM and PCR of immunoglobulin or T-cell receptor gene clonal rearrangements and BCR-ABL1, KMT2A-AF4 and E2A-PBX1 fusion genes.
Results: On day 26, both FCM and PCR seemed to have good discrimination sensitivity for overall survival (P = .001 to .008) and progression-free survival (P = .03 to .04) prediction for both Philadelphia-positive and -negative cases. The most sensitive method in week 11 was PCR including all results > 0 considered to indicate MRD positivity (P = .002 for overall survival and P = .02 for progression-free survival). PCR with other cutoffs was not sufficiently sensitive in week 11. Moreover, no FCM+ samples were found in week 11. The subanalysis of the Philadelphia-negative patients showed similar results.
Conclusion: Our analysis showed that both FCM and PCR MRD assessment methods are sensitive for survival prediction during induction. However, we believe FCM could not be sufficiently sensitive in later phases of treatment.
Keywords: ALL; FCM; MRD; Overall survival; Sensitivity.
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