Management of hairy cell leukemia variant

Hairy cell leukemia variant (HCL-V) is now included in the World Health Organization (WHO) classification as a provisional entity and is no longer considered to be biologically related to classic HCL (HCL-C). The clinical course of HCL-V is variable but usually more aggressive, and the median survival of patients with HCL-V is significantly shorter than that of HCL-C. The therapeutic approach to HCL-V is still debated. Various treatment approaches active in HCL-C achieve partial response (PR) or no response in HCL-V, and remission is usually shorter than in HCL-C. In addition, HCL-V seems to be resistant to therapeutic modalities usually highly effective in the treatment of HCL-C. Cladribine (2-CdA) is significantly less active in HCL-V than in HCL-C. In addition, the majority of patients with HCL-V require more than one cycle of 2-CdA to maintain PR. Patients with HCL-V treated with pentostatin also have a poorer clinical outcome and a lower response rate than those of patients with HCL-C. Recently, some reports indicate that monoclonal antibodies, rituximab and alemtuzumab, are active in HCL-V. Promising results have also been obtained with anti-CD22 immunotoxin, BL22. A new generation of CD22-specific immunotoxins, moxetumomab pasudotox (CAT-8015, HA22), highly active in refractory/relapsed HCL-C, also need clinical investigation in HCL-V. Currently, immunochemotherapy with rituximab and purine nucleoside analogs (PNAs) should be considered as the treatment of choice in previously untreated patients.