2-chlorodeoxyadenosine (cladribine) in the treatment of hairy cell leukemia and hairy cell leukemia variant: 7-year experience in Poland

Between January 1991 and December 1997, 103 patients, 97 with typical hairy cell leukemia (HCL) and 6 with HCL-variant (HCL-V) were treated with 2-chl orodeoxyadenosine (2-CdA) given as 2-h infusion for 5 consecutive d at a da ily dose 0.12 mg/kg. To our knowledge this is the largest cohort of HCL pat ients treated with this type of regimen. Median follow-up amounted to 36 mo nths. Fifty-six of 97 patients with typical HCL were newly diagnosed and 41 were relapsed after previous treatment. Splenectomy as a first-line therap y was performed in 23 patients and Is remaining patients received prednison e, chlorambucil or interferon-alpha (IFN-alpha) alone or in combinations. S eventy-five (77.3%) patients entered CR and 18 (18.6%) achieved PR, giving an overall response rate of 95.9%. The mean time of first CR duration amoun ting to 32 months (range 3-72) did not correlate to the number of 2-CdA cyc les. 2-CdA was equally effective in treatment of newly diagnosed patients a nd patients who relapsed after previous therapeutic procedures. Relapse of the disease occurred in 20 of 75 patients who achieved CR after 2-CdA and w as usually manifested by very discrete changes in peripheral blood counts ( neutropenia and/or relative lymphocytosis). The mean progression-free survi val (PFS) time in this group was 37.4 (range 10-66) months. Ten of 20 relap sed patients were retreated with 2-CdA given an identical course to the fir st one. Seven patients entered second CR lasting 19+ (range 847) months and 3 experienced PR. This confirms the previous observations that 2-CdA gives no resistance to leukemic clone. Ten remaining patients have not required retreatment so far and remain in a good clinical and hematological state. T he results of HCL-V treatment with 2-CdA were poor. Only 2 patients achieve d PR and 4 patients did not respond to this drug. Seven patients (5 with ty pical HCL and 2 with HCL-V) died, 3 of causes unrelated to the disease. Sec ond neoplasms were noted in 5 patients. 2-CdA-related side effects resulted mainly from myelosuppression and infectious complications. In conclusion w e confirm the effectiveness of 2-CdA in inducing CR in patients with typica l HCL, but this drug is unable to completely eradicate the leukemic clone w hich results in the relapse of the disease. The real incidence of the relap se rate may be underestimated unless bone marrow biopsy is performed. The r esults of our study indicate that a 2-h infusion of 2-CdA in HCL patients i s at least as effective as a 24-h infusion but more convenient to the patie nts, and may be given on an outpatient basis.