CD19 and acute lymphoblastic leukemia: A long-term follow-up clinical trial showed that relapsed B-ALL patients with a low disease burden, who were treated with CD19 CAR T Therapy, had longer long-term survival and a lower incidence of the cytokine release syndrome and neurotoxic events than did patients with a higher tumor load [22], supporting critical role of early detection of CPMRD in effectively managing relapsed patients with preemptive therapy like CAR T immunotherapy.