Clinical significance of ZAP-70 protein expression in B-cell chronic lymphocytic leukemia

The clinical course of B-cell chronic lymphocytic leukemia (B-CLL) is variable, and novel biologic parameters need to be added to the clinical staging systems to predict an indolent or aggressive outcome. We investigated the 70-kDa zeta-associated protein (ZAP-70), CD38, soluble CD23 (sCD23), and cytogenetics in 289 patients with B-CLL. Both a shorter progression-free survival (PFS) and overall survival (OS) were observed in ZAP-70(+) (P < .001), in CD38(+) (P < .001) and in sCD23(+) patients (P < .001 and P = .013, respectively). ZAP-70(+)CD38(+) or ZAP-70(+) patients with an unmutated IgV(H) status showed both a shorter PFS (P < .001) and OS (P < .001 and P < .001, respectively) as compared with ZAP-70(-)/CD38(-) or ZAP-70(-) patients with mutated IgV(H) genes. Discordant patients showed an intermediate outcome. Note, ZAP-70(+) patients even if CD38(-) or mutated showed a shorter PFS, whereas ZAP-70(-) patients even if CD38(+) or unmutated had a longer PFS. Furthermore, ZAP-70 positivity was associated with a shorter PFS both within normal karyotype (P < .001) and within the poor-risk cytogenetic subset (P = .02). The predictive value of ZAP-70 expression was confirmed in multivariate analysis. Thus, ZAP-70 protein determined by flow cytometry improves the prognostic significance of cytogenetics and appears to be a better predictor of outcomes than IgV(H) gene mutational status. On this line, we recommend and are also interested in conducting a prospective randomized trial of early intervention versus observation for ZAP-70(+) patients.