Use of flow cytometry during induction chemotherapy to determine outcomes in acute myeloid leukemia.

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7104 Background: The use of MRD to predict outcome in AML is controversial. We sought to determine concordance between FC and BM biopsy morphology on day 14 (D14BM) and CR bone marrow (CRBM) specimens and whether MRD detected by FC predicted for inferior outcomes. Methods: We performed a retrospective analysis of adult AML patients treated between 2005 and 2010 with standard induction chemotherapy. Based upon BM morphology and FC, patients were designated as BM+FC+, BM+FC-, BM-FC+, or BM-FC-. Outcomes assessed included induction failure, RFS and OS. Results were adjusted for age at diagnosis, NCCN risk classification, and secondary AML status. Results: Of 287 evaluable patients, 74 had D14 BM and FC results and 98 had CR BM and FC results. Using BM morphology as the gold standard, discordance rates for the presence and absence of disease for the D14 BM by FC were 29% and 23% respectively. Multivariate analysis revealed that patients categorized as BM-FC+ at D14 were more likely to experience induction failure (HR 8.62, CI 0.36-208) and had lower RFS and OS (HR 1.47, 1.95 CI 0.40-5.41, 0.52-7.36 respectively). Analysis of the CR BM samples showed similar results. Conclusions: In this retrospective study there was a high discordance rate between FC and BM morphology on D14 BM and CR BM. While there was a trend toward inferior patient outcomes when disease was detected by FC but not morphology, this was not statistically significant. Limitations of our study include the retrospective nature of the analysis, paucity of patient samples that had a FC evaluation, lack of data to see if positive FC at D14 or CR changed clinician therapy choices and interpretation bias by pathologists as a result of access to FC results during BM morphology interpretation. Larger prospective studies are needed to evaluate whether MRD detected by FC as early as D14 during AML therapy affects clinical outcomes.