Classic hairy cell leukemia (HCL) is a rare indolent B‑cell lymphoproliferative disorder. First described as a distinct disease entity by Bouroncle et al. in 1958, HCL inherited a dismal survival prognosis of less than 5 years [
1]. In the absence of effective systemic therapeutic options splenectomy was treatment of choice for decades, only allowing for short-lived remissions [
2]. The first substantial therapeutic intervention in this previously “untreatable” chronic leukemia was made with the introduction of interferon‑α (IFN‑α) in 1984 with response rates of 80–90 % (≤90 % partial remissions, PR; ≤40 % complete remissions, CR) and extension in survival [
3‐
6]. Only shortly thereafter, however, HCL was found to be highly sensitive for purine analogues, an observation that rapidly altered the natural history of HCL. Facilitating a near normal life span in the majority of patients, purine analogues have become first line therapy for HCL [
7,
8]. Inferior in terms of quality and duration of response, nowadays IFN-α is rarely treatment of choice. Moreover, novel therapeutic tools for patients with relapsed or refractory disease after purine analogues have emerged such as rituximab and, more recently, vemurafenib [
9‐
13]. In the absence of long-term safety data for these novel agents, however, induction and maintenance therapy with IFN-α may still represent a viable therapeutic option when the profound immunosuppressive side effects of purine analogues are to be avoided, e. g., in the presence of significant comorbid conditions and ongoing infectious complications. We herein report a HCL patient, who has received multiple lines of therapy, including pentostatin, cladribine, and a total of 164 months of treatment with IFN-α yielding long-term disease control (Table
1).
Table 1
Clinical outcome of consecutive treatments in our HCL patient
1 | Splenectomy | – | 05/1982 | – | PR | 12 months | None |
2 | Interferon-α | 1.5 × 106 U/week | 06/1983–06/1986 | 36 months | PR | 36 months | None |
3 | Pentostatin | 4 mg/m² | 07/1986–03/1987 | 8 monthsa
| CR | 163 months | Recurrent infectious complications due to prolonged neutropenia |
4 | Interferon-α | 4.5–9 × 106 U/week | 01/2000–11/2007 | 95 months | PR | 95 months | None |
5 | Cladribine | 0.14 mg/kg/day | 11/2007 | 5 days (1 cycle) | CR | 49 months | Recurrent infectious complications due to prolonged neutropenia |
6 | Interferon-α | 4.5 × 106 U/week | 12/2011–08/2014 | 33 months | PR | 33 months | None |