Efficacy of anti-CD20 monoclonal antibodies (Mabthera) in patients with progressed hairy cell leukemia

Background and Objectives. Recently, a chimeric monoclonal antibody (MoAb) directed against the CD20 antigen (rituximab) has been successfully introdu ced in the treatment of several CD20-positive B-cell neoplasias and particu larly of follicular lymphomas. Based on these premises we evaluated the eff icacy and the toxicity of chimeric anti-CD20 monoclonal antibody (MoAb) in relapsed/progressed hairy cell leukemia (HCL). Design and Methods. Ten patients with relapsed/progressed HCL entered the s tudy. Eight patients were males and two females with a median age of 55 yea rs (range 41-78) and all of them had been previously treated with 2-chlorod eoxyadenosine and/or deoxycoformycin and (x-interferon. Two out of 10 patie nts were anemic (Hb < 10 g/dL), 4 thrombocytopenic (Pit < 100x10(9)/L), 3 h ad fewer than 1.0x10(9)/L neutrophils and 3 had circulating hairy cells (HC ). All patients received 375 mg/m(2) Lv. of anti-CD20 MoAb once a week for 4 doses. Results. All patients were evaluable for response, one patient showing a co mplete remission and 4 a partial response. Adverse reactions, such as fever , chills, bone pain, hypotension and thrombocytopenia, were transient and m ild (grade 1-2) and occurred only during the first course of treatment. One month after the last infusion, patients who had had anemia, neutropenia or thrombocytopenia, recovered normal peripheral blood values. Circulating HC also disappeared within one month. Immunostained bone marrow biopsies were checked 1, 3 and 6 months after the end of therapy and in 5 out of 10 pati ents a > 50% reduction of bone marrow HC infiltration was recorded. Interpretation and Conclusions. On the basis of these preliminary results o bserved in 10 patients with progressed HCL, it appears that treatment with anti-CD20 MoAb is safe and effective in at least 50% of patients, particula rly in those with a less evident bone marrow infiltration (less than or equ al to 50%) and in those previously splenectomized. (C) 2001, Ferrata Storti Foundation.