Long-term clinical outcome of a weekly 2-chlorodeoxyadenosine regimen in treatment-naïve patients with hairy cell leukemia

Hairy cell leukemia (HCL) has a favorable clinical outcome with appropriate treatment; however, further research is needed on managing patients with relapsed or refractory disease and the risk of infection during prolonged periods. This study examined the long-term effects of 2-chlorodeoxyadenosine (2-CdA), particularly using a weekly infusion protocol, in treatment-naïve patients with HCL. This retrospective study evaluated the long-term follow-up data from 21 South Korean patients diagnosed with HCL. Among them, 20 patients were treated with a weekly infusion protocol (0.14 mg/kg/day over 5-6 weeks), whereas one received daily continuous intravenous infusion (0.1 mg/kg/day over 7 days). The median age and follow-up period of the patients were 50 (range, 32-77) years and 39.0 (range, 7.3-223.3) months, respectively. None of the patients with HCL died from 2-CdA-related toxicity. One patient preferred a daily treatment schedule for shorter durations, and this patient required prolonged hospital stay due to an anal abscess. The overall survival (OS) was 85.7% (95% confidence interval [CI], 33.4-97.9), without reaching the median OS. The progression-free survival (PFS) was 31.3% (95% CI, 5.6-62.3), with a median PFS of 66.5 months. Among the 19 patients who achieved remission, 5 relapsed (26.3%), with a median cumulative incidence of relapse of 116.7 months. The non-relapsed mortality rate was 13.6% (95% CI, 0.4-49.1). Weekly 2-CdA provides enhanced flexibility in clinical practice, with excellent long-term OS and PFS rates, making it a valuable treatment option for patients with HCL in an outpatient setting.