In this prospective randomized trial, we compared the efficacy and toxicity of cladribine (2-CdA) alone to 2-CdA combined with cyclophosphamide (CC) or cyclophosphamide and mitoxantrone (CMC) in untreated progressive chronic lymphocytic leukemia (CLL). Study end points were complete response (CR), overall response, minimal residual disease (MRD), progression-free survival, overall survival, and toxicity. From January 1, 1998 to December 31, 2003, 508 patients from 15 hematology departments were randomized. Compared with 2-CdA, CMC induced higher CR rate (36% vs 21%, P ؍ .004), and a trend for higher CR rate with CC was observed (29% vs 21%, P ؍ .08). Furthermore, the percentage of patients who were in CR and were MRD negative was higher in CMC compared with 2-CdA (23% vs 14%, P ؍ .042). There were no differences in overall response, progressionfree survival, and overall survival among treatment groups. Grade 3/4 neutropenia occurred more frequently in CC (32%) and CMC (38%) than in 2-CdA (20%) (P ؍ .01 and P ؍ .004, respectively). Infections were more frequent in CMC compared with 2-CdA (40% vs 27%, P ؍ .02).In conclusion, CMC used in first-line treatment of CLL results in a higher CR rate and suppresses MRD more efficiently than 2-CdA monotherapy, although associates with increased toxicity. No important differences in efficacy and toxicity were found between CC and 2-CdA regimens.
The purine nucleoside analogues (PNAs), fludarabine (FA), 2-CdA (2-chlorodeoxyadenosine, 2-CdA) and pentostatin (2'-deoxycoformycin, DCF) represent a group of cytotoxic agents with high activity in lymphoid and myeloid malignancies. PNAs share similar chemical structure and mechanism of action. Several mechanisms could be responsible for their cytotoxicity both in proliferating and quiescent cells, such as inhibition of DNA synthesis, inhibition of DNA repair and accumulation of DNA strand breaks. Induction of apoptosis through the mitochondrial pathway, direct binding to apoptosome or modulation of p53 expression all lead to apoptosis, which is the main end-point of PNA action. However, individual PNAs exhibit significant differences, especially in their interaction with enzymes involved in adenosine and deoxyadenosine metabolism. Synergistic interactions between PNAs and other cytotoxic agents (alkylating agents, anthracycline antitumor antibiotics, cytarabine, monoclonal antibodies) have been demonstrated in both preclinical and clinical studies. PNAs are highly effective in chronic lymphoid leukemias and low grade B- and T-cell non-Hodgkin's lymphomas, including Waldenström's macroglobulinemia. DCF and 2-CdA are currently the drugs of choice in hairy cell leukemia. Moreover, clinical studies have confirmed the efficacy of PNAs alone or in combination protocols in the treatment of acute myeloid leukemia and myelodysplastic syndromes. Finally, PNAs, especially FA, play an important role in non-myeloablative conditioning regimens for allogenic stem cell transplantation in high-risk patients. The toxicity profiles of PNAs are similar for all agents and consist mainly of dose-limiting myelotoxicity and prolonged immunosuppression. Three other compounds: clofarabine, nelarabine and immucillin-H are currently being evaluated clinically.
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