Extended F ollow-Up o f P atients W ith H airy C ell L eukemia After T reatment W ith C ladribine

Purpose: Hairy cell leukemia (HCL) is an uncommon, indolent, chronic B-cell lymphoproliferative disorder involving the marrow and spleen. Therapy for HCL includes splenectomy, interferon alfa-2a and alfa-2b, pentostatin, and cladribine. The purpose of this article was to report the extended follow-up of HCL patients treated with cladribine. Patients and Methods: Two hundred nine patients with HCL who were treated with cladribine had at least 7 years of follow-up. A course of cladribine constituted a 7-day continuous intravenous infusion at a dose of 0.1 mg/kg/d. Results: Of the 207 assessable patients who had at least 7 years of follow-up, 196 (95%) achieved a complete response (CR) and 11 (5%) achieved a partial response (PR) after a single course of cladribine (overall response rate, 100%). The median first-response duration for all responders was 98 months. Seventy-six patients (37%) experienced relapse after their first course of cladribine. The median time to first relapse for all responders was 42 months. Time to treatment failure of CRs compared with PRs was statistically significant (P < .0005). The overall survival rate was 97% recorded at 108 months. Forty-seven patients developed 58 second malignancies. The observed-to-expected ratio for second malignancies was 2.03 (95% confidence interval, 1.49 to 2.71). Conclusion: These results confirm previous observations that single courses of cladribine administered to patients with HCL induce high response rates, the majority of which are CRs. Most patients enjoy long-lasting complete remissions, and those patients who experience relapse can be successfully re-treated with cladribine. J Clin Oncol 21:891-896. © 2003 by American Society of Clinical Oncology.