Treatment protocols for hairy cell leukemia (HCL) are provided below, including those for initial treatment, resistant disease, variant HCL, and relapsed/refractory HCL.
Symptoms requiring initiation of treatment
Many patients with classic HCL appear to be asymptomatic even after diagnosis, and about 10% will never require therapy.
Treatment should be initiated if the patient develops 1 or more of the following signs and symptoms:
Abdominal fullness or discomfort due to splenomegaly
Complaints of fatigue, weakness, and weight loss
Platelet count < 100,000/μL
Recurrent infections, which may be life-threatening, secondary to granulocytopenia and monocytopenia (absolute neutrophil count < 1000/µL; see the Absolute Neutrophil Count calculator)
Symptomatic anemia with a hemoglobin concentration < 11.0 g/dL
Initial treatment recommendations
The purine analogues cladribine and pentostatin are first-line agents in the treatment of HCL. Cladribine is more commonly used because of ease of administration.
Cladribine 0.09 mg/kg/day by continuous IV infusion for 7d (FDA approved) or 0.14 mg/kg/day IV over 2h or SC for 5d; 5-6 weekly doses of 0.14 mg/kg have also been studied
(cost, inconvenience, and adverse reactions less likely with SC; can use growth factors if febrile neutropenia develops) or
Pentostatin 4 mg/m2 IV bolus or over 30min every 2wk with 1.5 L of hydration for each dose for 3-6mo or
Interferon alfa 2b 2 million U/m2 SC 3 times per week for 12-18mo for relapsed or refractory HCL
Splenectomy (laparoscopic preferred) is considered for patients with bleeding from severe thrombocytopenia or failure to respond to systemic therapy; administer pneumococcal, meningococcal, and Haemophilusinfluenzae vaccines prior to surgery
Variant hairy cell leukemia
Variant hairy cell leukemia is resistant to the standard treatments, which include the use of purine analogues and interferon alfa. Combinations of rituximab and purine analogs are under evaluation.
Patients may relapse after initial treatment, so it is important to administer a second cycle of treatment as that can lead to another remission.
Although pentostatin and cladribine provide responses in greater than 85% of patients, and a median progression-free survival of up to 15 years, alternative treatments (eg, the addition of rituximab
) are needed for patients whose disease becomes refractory to these treatments.
Moxetumomab pasudotox is an anti-CD22 recombinant immunotoxin indicated for adults with relapsed or refractory hairy cell leukemia (HCL) who have received at least 2 prior systemic therapies, including a purine nucleoside analog.
Dose: 0.04 mg/kg IV on days 1, 3, and 5 of each 28-day cycle; infuse over 30 minutes; continue for maximum of 6 cycles or until disease progression or unacceptable toxicity occurs.
Drugs that are being evaluated in clinical trials include ibrutinib (first class oral inhibitor of Bruton kinase) and BRAF V600E inhibitors as the majority of classic HCL harbors the BRAF mutation.