Rituximab anti-CD20 monoclonal antibody induces marked but transient reductions of peripheral blood lymphocytes in chronic lymphocytic leukaemia patients.

Rituximab has been recently proposed as an effective non-chemotherapeutic option for patients with follicle centre lymphoma (FCL). However, less is known on its role in chronic lymphocytic leukaemia (CLL). We thus decided to assess its effectiveness on a panel of 7 patients with refractory or relapsed CLL. Mild (5 patients) or severe (1 patient) adverse reactions were observed during the first hours of Rituximab infusion, almost exclusively at the first course. Symptoms rapidly subsided with temporary drug withdrawal and low dose steroids. All patients could receive the whole scheduled treatment. A striking reduction of peripheral blood (PB) lymphocyte counts was observed in all patients (median 93%; range 57-99%). However, Rituximab was poorly effective towards nodal and splenic disease. Patients required additional treatment after a median time of 70 d (range: 20-180 d). Our data show that Rituximab delivery in CLL patients is feasible and has an acceptable toxicity, although it probably does not represent an ideal treatment option when delivered using schedules originally designed for FCL patients. However, responses observed at PB level suggest that Rituximab has an activity which is not negligible and deserves further investigation in CLL. Future approaches will be directed to the development of alternative schedules which may include dose intensification, combination of Rituximab and chemotherapy, and in vivo purging of peripheral blood progenitor cell harvests for autografting procedures.