Program: Oral and Poster Abstracts
Session: 612. Acute Lymphoblastic Leukemia: Clinical Studies: Poster II
Objectives: The aims of this study were to assess MRD by flow-cytometry in relapsed ALL and to evaluate its prognostic impact as a predictor factor of outcome at the end of the induction therapy and prior to hematopoietic stem cell transplantation (HSCT).
Patients and Methods: From Aug’10 to Jun’15, 123 ALL patients were treated at our center. MRD determination at least at two time-points during relapse treatment was a requirement for considering a patient eligible for the present study. Sixty-six cases were excluded due to the following causes: 10 patients died during induction, 2 died early in complete remission (CR), 29 did not respond to chemotherapy, in 13 patients MRD determination was not performed: 4 did not have clinical data available, 4 patients were Down Syndrome and 4 children received treatment for relapse in other centers. Thus, fifty-seven patients achieved CR and were evaluated for MRD at two time points. Of them, 56 patients belonged to S4 and S3 and 1 patient to S1 group as defined by the Berlin-Frankfurt-Münster stratification for relapsed ALL. MRD was analyzed by multiparametric flow-cytometry following ALL-IC 2009 guidelines. Negative MRD was defined as disclosing less than 0.1% of blasts. For this analysis, patients were stratified based on MRD levels at two different time points: after end of induction, before HSCT or at any other time point during the follow-up for patients who did not undergo HSCT. Three groups were defined: Group-1: negative at both time points (n= 23), Group-2: positive at 1 time point (n= 13) and Group-3: positive at both time points (n= 21). Patients who relapsed before receiving HSCT were considered Group-3. Twenty-five patients underwent HSCT: 13 of them from Group-1, 9 from Group-2 (2 had positive MRD previous to receive HSCT) and 3 patients from Group-3. HSCT was performed with matched familiar donor in 16 cases and matched unrelated donor in 9 cases.
Results: The distribution of events according to receiving or not HSCT was: 5 died due to transplant related mortality (TRM), 9 relapsed after receiving HSCT and 16 during treatment with chemotherapy. With a median follow-up of 16 (range: 6-67) months, overall 3-year EFS probability (EFSp) (SE) was 32 (8)%. The 3-year EFSp was 75 (11)% for Group-1, 24 (14)% for Group-2 and 0% for Group-3 (p-value <0.00001). Comparing patients who did not receive HSCT vs. patients who did, EFSp (SE) was 32 (12)% and 29 (11)% respectively (p-value: non-significant). The EFSp (SE) according to MRD groups in patients who underwent HSCT was: Group-1: 53 (19)%, Group-2: 14 (13)% and 0% for Group-3 (p-value: 0.06).
Conclusions: MRD quantification by flow-cytometry demonstrated to be a significant prognostic factor for relapsed ALL. Both, TRM and death in CR rates, were high and should be decreased by improving supportive measures. MRD determination by flow-cytometry in patients who underwent HSCT showed a trend to achieve a better EFSp, thus representing a relevant tool for stratifying relapsed ALL patients in order to achieve a better selection of patients to receive HSCT.
Disclosures: No relevant conflicts of interest to declare.
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