[Clinical Significance of Minimal Residual Disease in Pediatric Patients with B-cell Acute Lymphoblastic Leukemia].

Objective: To explore the consistency of flow cytometry (FCM) method and polymerase chain reaction (PCR) technique in the detection of minimal residual disease (MRD) at different treatment stages in pediatric patients with B-cell acute lymphoblastic leukemia (B-ALL) and the correlations between the detection results and prognosis.

Methods: The clinical data of 64 newly diagnosed pediatric patients with B-ALL admitted to the Department of Pediatrics of Peking University People's Hospital from January 2005 to December 2017 were retrospectively analyzed. FCM and PCR methods were used to monitor the MRD level in bone marrow samples from 64 children during the same period of treatment on d33 and d90 respectively, and the detection results were analyzed.

Results: There were 37 males and 27 females in the 64 patients, with a median age of 8 years(range 0.8 to 16 years). The complete remission (CR) rate after the first cycle of induction chemotherapy was 98.4% (62/63), with overall CR rate of 100%. 12 patients experienced recurrence, with a median recurrence time of 16.9 (5.3-46.3) months. The median follow-up time of the 64 patients was 77.2 (1.0-184.8) months , and the 5-year overall survival (OS) rate and event-free survival (EFS) rate were 82.8%±4.7% and 75.0%±5.4%, respectively. On d90, the concordance rate of the MRD results from the two methods was 98.4%, and the related kappa value was 0.792 ( < 0.001), which were significantly higher than those on d33. After induction chemotherapy (d33), the 5-year EFS rate of MRD-FCM group (79.3%±5.3%) was significantly better than that of MRD-FCM group (40.0%±21.9%) ( =0.028), there were no significant differences in the 5-year OS rate and EFS rate between MRD-PCR group and MRD-PCR group, and the 5-year EFS rate of MRD-FCM/PCR group (85.4%±5.5%) was significantly better than that of MRD-FCM/PCR group (40.0 %±21.9%) ( =0.026).

Conclusion: In children with B-ALL, the MRD results detected by FCM and PCR methods show good consistency, especially in consolidation therapy period (d90). The MRD level at the end of induction therapy (d33) is an important factor affecting the long-term prognosis, especially the MRD results detected by FCM method, which is significantly associated with prognosis.