Objective: To study the predictable value of monitoring minimal residual disease (MRD) regularly by flow cytometry (FCM) in patients with acute leukemia (AL) in the first complete remission (CR(1)).
Methods: From April 2005 to July 2009, AL patients who had got CR(1) after chemotherapy were regularly monitored for MRD in bone marrow by FCM to relapse or to July 2010 in Beijing Daopei Hospital (not including those received stem cell transplantation). The special antibody combinations were employed for each patient according to aberrant expression of leukemia cells. MRD(+) was defined as the aberrant cells more than 0.01%. The probability of continuous CR (CCR) was calculated by Kaplan-Meier formula, and the statistical difference between two CCR probabilities was evaluated by log-rank test.
Results: A total of 163 AL patients in CR(1) were monitored to relapse or to July 2010. Among 89 AML patients referred to our hospital within 1 year after diagnosis, 30 cases were in MRD(+) and 59 cases MRD(-) till 12 months following chemotherapy, 3/30 patients in MRD(+) and 47/59 remained in CCR to July 2010. The probability of CCR at 24, 36 months was 13%, 13%in MRD(+) group, 94%, 78% in MRD(-) group respectively, the difference between them was statistically significant (P < 0.01). Among 35 ALL referred to our hospital within 5 months after diagnosis, 13 cases were MRD(+) and 22 cases MRD(-) till 5 months following chemotherapy, 0/13 patients in MRD(+) and 20/22 patients in MRD(-) remained in CCR to July 2010. The probability of CCR at 24, 36 months was 0% in MRD(+) group, 96%, 96% in MRD(-) group respectively, the difference between them was statistically significant (P < 0.01). Over the time point above, all patients with MRD(+) or their MRD from negative to positive relapsed finally, and most patients with MRD(-) remained CCR to July 2010.
Conclusion: It had a clinical prognostic value to monitor MRD regularly by FCM in the patients with AL after CR(1).