OBJECTIVETo study the significance of flow cytometric monitoring minimal residual diseases (MRD) in patients with acute leukemia (AL) after allogeneic hemapoietic stem cell transplantation (HSCT).

METHODSFrom January 2007 and January 2008 MRD were detected by flow cytometry (FCM) in 402 bone marrow (BM) in 102 AL patients without leukemic gene and chromosomal changes at first diagnosis after HSCT (1, 2, 3, 6,12 months after HSCT; adding detection frequency in part of high risk patients), The relationship between the MRD results and clinical prognosis were observed. Patients with significantly higher MRD were treated and the effectiveness was monitored by FCM (MRD > 0.01% considered as positive).

RESULTS(1) 71 cases were persistently negative for MRD after HSCT and all them were in hematologic complete remission (CR). Only 3 cases had extramedullary relapse. The disease free survival (DFS) and overall survival (OS) were 66.2% and 90.1%, respectively. (2) Of 27 MRD(+) cases 11 converted to MRD negativity after chemotherapy plus donor lymphocyte infusion (DLI), CIK, NK cells. The DFS and OS were 63.6% and 72.7%, respectively. Other 16 cases had hematologic relapse. The DFS and OS were 11.1% and 25.0%, respectively. The median time from MRD increasing to hematologic relapse was 48 days (7-69 day). (3) Four cases had hematologic relapse after HSCT and died in the end.

CONCLUSIONS(1) The DFS and the OS in MRD(-) cases are significantly higher than those of MRD(+) cases. (2)MRD(+) patients after HSCT coveted to MRD(-) after intervention. Therapy, whose DFS and the OS are still significantly higher than those of MRD(+) cases. (3) Patients with hematologic relapse after HSCT have the worst prognosis and the DFS and OS are significantly low. FCM monitoring of MRD in patients after HSCT is a sensitive, specific, quick and simple method. It can indicate recurrent state in time, facilitates early intervention, reduces the hematologic relapse risk and improves DFS.