Clearing MRD positivity with blinatumomab in pediatric B-cell acute lymphoblastic leukemia: insights from droplet digital PCR and flow cytometry

Blinatumomab has shown to improve survival outcomes in B-cell acute lymphoblastic leukemia (B-ALL) patients with measurable residual disease (MRD) detected by multiparametric flow cytometry (MFC). However, data on blinatumomab clearing MRD with high sensitivity remain scarce. This study evaluates the effectiveness of blinatumomab in eradicating low levels of MRD, as detected by droplet digital PCR (ddPCR) but undetectable by MFC, in children with B-ALL. Patients (n = 9) whose MRD was undetectable by MFC but detectable by ddPCR after chemotherapy and followed by blinatumomab consolidation were included retrospectively. After the administration of blinatumomab, 5 out of 9 patients (55.56%) successfully achieved undetectable levels of ddPCR-MRD. Notably, among the 4 patients with BCR::ABL1 gene-positive acute lymphoblastic leukemia (ALL), only one achieved gene negativity. Starting from the initiation of blinatumomab treatment, with a median follow-up of 12 months, all patients remained in complete remission. Our study was the first to demonstrate that blinatumomab could further eradicate ddPCR MRD after patients achieve MFC-MRD undetectable status in B-ALL patients.