MULTIDIMENSIONAL FLOW-CYTOMETRY OF MARROW CAN DIFFERENTIATE LEUKEMIC FROM NORMAL LYMPHOBLASTS AND MYELOBLASTS AFTER CHEMOTHERAPY AND BONE-MARROW TRANSPLANTATION

Serial bone marrow aspirates from patients previously given a diagnosi s of acute lymphoblastic leukemia (ALL) who had undergone chemotherapy , bone marrow transplantation (BMT), or both were analyzed bq, multidi mensional flow cytometry (MDF) to detect residual disease (lower limit of detection 0.3%). Correlation between the results of morphologic ex amination and MDF showed concordant results on 100 of 118 specimens. T he MDF-positive, morphologic examination-negative specimens were posit ive by cytogenetic examination or were obtained from patients in whom the ALL eventually, relapsed Similar correlations between MDF and the results of cytogenetic examination were obtained. Leukemic cells were detected in 29 of 62 patients before BEAT and 12 of 52 after BMT. Norm al regenerating lymphoblasts were identified and quantified by MDF in patients without detectable leukemic lymphoblasts. Patients with leuke mic lymphoblasts found by MDF in specimens obtained immediately before BMT were 3.28 times more likely to experience relapse after BMT compa red with MDF-negative patients, even when leukemic lymphoblasts were u i?detectable by histopathologic examination, cytogenetic examination o r both. All patients who had undergone BMT with leukemic lymphoblasts found by MDF, with or without morphologic or cytogenetic confirmation experienced relapse according to conventional criteria within 42 days of the MDF analysis. The detection of residual disease before overt re lapse may provide information for early intervention, while definitive recognition of normal recovering blasts may prevent unnecessary treat ment.