The addition of rituximab to fludarabine improves clinical outcome in untreated patients with ZAP‐70‐negative chronic lymphocytic leukemia

Abstract

Clinical trials of monoclonal antibodies in combination with chemotherapy have reported previously unattained response rates in patients with B-cell chronic lymphocytic leukemia (B-CLL); however, the analysis of ZAP-70 protein and/or CD38 may explain better the discordant outcomes independent of treatment. The authors conducted a Phase II study, in which rituximab was added to fludarabine for patients with symptomatic, untreated CLL, to evaluate clinical outcomes. Sixty patients with B-CLL received 6 monthly courses of fludarabine (25 mg/m(2) for 5 days) followed by 4 weekly doses of rituximab (375 mg/m(2)). On the basis of National Cancer Institute criteria, 47 of 60 patients (78%) achieved a complete remission, 9 of 60 patients (15%) achieved a partial remission, and 4 of 60 patients (7%) had no response or progressive disease. It is noteworthy that the patients experienced a long progression-free survival (PFS) from treatment (68% at 3 yrs). A significantly shorter PFS was observed in ZAP-70-positive patients (25% vs. 100% at 3 yrs; P = 0.00005), in CD38-positive patients (18% vs. 91% at 3 yrs; P = 0.0002), and in patients who had more minimal residual disease (36% vs. 77% at 2.5 yrs; P = 0.001). With the addition of rituximab to fludarabine, improved clinical outcomes were obtained, and the stratification of patients by using ZAP-70 and CD38 may help clinicians offer more aggressive and/or experimental approaches to the treatment of patients with high-risk B-CLL subtypes.