Treatment of hairy-cell leukemia with cladribine: response, toxicity, and long-term follow-up.

Purpose: To analyze initial and long-term outcomes after treatment of patients with active hairy-cell leukemia (HCL) with a single cycle of cladribine (2-CdA).

Patients And Methods: Forty-nine patients with active HCL were treated with 2-CdA by continuous intravenous infusion at 0.1 mg/kg/d for a total of 7 days at the Long Island Jewish Medical Center between September 1990 and August 1992. Here we report on all patients followed-up until April 1996.

Results: At 3 months after treatment, complete response (CR) occurred in 37 patients (76%) and partial response (PR) occurred in 12 patients (24%), for an overall response rate of 100% (95% confidence interval, 94% to 100%). At a median follow-up of 55 months, the relapse-free survival is 80% and overall survival is 95%. Ten patients (20%) have relapsed. Of the 26 patients in whom lymphocyte phenotyping was performed, four were found to have a CD25-negative phenotype. All four of these patients had PRs only and all relapsed. Eight patients have been re-treated with 2-CdA, and all achieved at least a partial remission; two of these have already relapsed with remission durations of less than 1 year. Five second malignancies have occurred in four patients.

Conclusion: With a median follow-up of more than 4 years, 39 patients (80%) continue in remission. Only two deaths have occurred. A CD25-negative phenotype may predict for a poorer response to 2-CdA. Patients who relapse may be re-treated with 2-CdA, but subsequent remissions may be of shorter duration. There has not been a markedly increased incidence of second malignancies or late opportunistic infections.