Relevance of CD20 antigen expression among paediatric patients with B‐lineage acute lymphoblastic leukaemia

Summary Literature regarding prognostic relevance of CD20 antigen expression among paediatric B‐lineage acute lymphoblastic leukaemia (B‐ALL) patients is sparse and contradictory. We analysed clinical laboratory parameters and survival characteristics pertinent to CD20 expression among 224 treatment‐naïve paediatric B‐ALL patients. 50% patients had CD20 expression (CD20+ B‐ALL). There was no difference in the clinical & laboratory presentation and end of induction measurable residual disease (EOI‐MRD) status according to CD20 expression. As compared to CD20− B‐ALL patients, CD20+ B‐ALL patients had two times more relapse (16% vs. 29%, p = 0.034), inferior relapse‐free survival (79% vs. 66%, p = 0.025) but no difference in overall survival (75% vs. 69%, p = 0.126). Similar to high‐risk NCI status and EOI‐MRD positivity, CD20 expression was an independent predictor for inferior relapse‐free survival (HR: 1.860, 95% CI: 1.008–3.432, p = 0.047). Compared to baseline, there was a significant increase in CD20‐expressing EOI‐residual blasts among CD20− B‐ALL patients (5% vs. 13%, p = 0.001). EOI residual blasts of both CD20+ and CD20− patients had three times increased normalized CD20 expression intensity (nCD20), with the intensity among CD20− B‐ALL patients reaching the pretreatment nCD20 of CD20+ B‐ALL patients (4.9 vs. 3.6, p = 0.666). Rituximab can be considered in managing EOI‐MRD‐positive CD20− B‐ALL patients as the residual blasts of these patients have quantitative and qualitative increases in CD20 expression.