Adverse prognostic significance of CD20 expression in adults with Philadelphia chromosome-negative B-cell precursor acute lymphoblastic leukemia

Abstract

The prognostic significance of CD20 expression in B-cell precursor acute lymphoblastic leukemia (BCP-ALL) has been mostly studied in children and yielded conflicting results. In 143 adults with Philadelphia chromosome-negative BCP-ALL treated in the multicentric GRAALL 2003 trial, CD20 positivity over 20% was observed in 32% of patients. While not influencing complete remission achievement, CD20 expression was associated with a higher cumulative incidence of relapse (CIR) at 42 months (P=0.04), independently of the ALL high-risk subset (P=0.025). Notably, the negative impact of CD20 expression on CIR was only observed in patients with a white blood cell count (WBC) over 30x10(9)/L (P=0.006), while not in those with a lower WBC. In the former subgroup, this impact translated into lower event-free survival (15% vs. 59% at 42 months, P=0.003). CD20 expression thus appears to be associated with a worse outcome, which reinforces the interest of evaluating rituximab combined to chemotherapy in CD20-positive adult BCP-ALL. ClinicalTrials.gov ID, NCT00222027.

Figure 1.

CIR according to (A) the ALL risk subsets and (B) CD20 expression. In 130 out of the 143 patients reaching first complete remission, CIR is influenced by the GRAALL risk classification and tends to be affected by CD20 expression.

Figure 2.

(A) CIR and (B) EFS according to CD20 expression and WBC. (A) From 130 patients in first complete remission, the negative impact of CD20 expression on CIR is only observed in the population of patients with higher (≥30x10⁹/L) WBC (P=0.006), but not in those with lower (<30x10⁹/L) WBC (P=0.77). (B) The negative impact of CD20 expression also translates into shorter EFS in patients with higher WBC (≥30x10⁹/L) while no effect is found in those with lower WBC (<30x10⁹/L).