Consensus guidelines for classic Hairy Cell Leukemia: induction therapy

On 2^nd February 2017, Michael R. Grever from the Ohio State University James Cancer Hospital, Columbus, OH, USA, and colleagues published consensus guidelines for the diagnosis and management of classic Hairy Cell Leukemia patients (HCLc) in the journal Blood.¹

Key Highlights:

• Immediate therapy may not be needed in approximately 10% patients; these patients should be closely monitored until treatment is needed
• Patients should be treated if their hematologic parameters are decreasing or if they show symptoms of the disease (such as symptomatic splenomegaly)
• It is recommended treatment is initiated before the patient has an active infection or blood parameters decline to dangerous levels
• Hematologic parameters indicating need for treatment include ≥1 of:
  • Hemoglobin <11g/dL
  • Platelet count <100,000/µL
  • Absolute neutrophil count <1,000/µL
• Hematologic parameters suggest that bone marrow function is compromised
• Induction in patients without active infection:
  • Primary nucleoside analog induction therapy: cladribine or pentostatin; decided by physician preference and patient convenience
  • Cladrabine: given on defined schedule, either 5-day/weekly for 6 weeks or 7-day continuous IV infusion; not used in patients with active infection and is highly myelosuppressive when given over one week
  • Pentostatin: given on alternate weeks until blood parameters nearly return to normal levels and splenomegaly has resolved on physician examination; demonstrated as effective treatment in patients with active infection,^2-3 and reduced doses have previously been administered to patients with complications from long-term myelosuppression
  • Both are very immunosuppressive; in patients without active infection, cladribine is thought to be the agent most often used
• Induction in patients with active infection:
  • Before beginning treatment with a purine analog, efforts should be made to control the infection
  • If the infection cannot be controlled but anti-leukemia therapy is required, primary therapy is either a purine analog or interferon alpha
  • Vemurafenib has been demonstrated to be an effective treatment option in relapsed HCLc patients who received purine analog induction therapy
  • Vemurafenib has been shown to increase peripheral blood counts and therefore increase infection control⁴ but this needs validating in clinical trials with HCLc patients with an active infection

The authors stated that standard chemoimmunotherapy cannot cure HCLc and treated patients remain at risk of relapse over time. However, induction therapies currently available for HCLc patients are fairly effective but immunosuppressive. After induction treatment with a purine nucleoside analog in particular, routine blood counts should be performed until recovery and patients should be closely followed in case of active infection or fever. The authors also note that, due to the success of standard therapy approaches, large numbers of patients are being treated outside of trials resulting in increasing inconsistency in the management and monitoring of HCLc patients. The authors concluded that these guidelines were developed with the aim of enhancing patient care and to offer a framework to continue improving HCLc patient outcomes.

Abstract:

Hairy cell leukemia is an uncommon hematologic malignancy characterized by pancytopenia and marked susceptibility to infection. Tremendous progress in the management of patients with this disease has resulted in high response rates and improved survival, yet relapse and an appropriate approach to re-treatment present continuing areas for research. The disease and its effective treatment are associated with immunosuppression. Because more patients are being treated with alternative programs, comparison of results will require general agreement on definitions of response, relapse, and methods of determining minimal residual disease. The development of internationally accepted, reproducible criteria is of paramount importance in evaluating and comparing clinical trials to provide optimal care. Despite the success achieved in managing these patients, continued participation in available clinical trials in the first-line and particularly in the relapse setting is highly recommended. The Hairy Cell Leukemia Foundation convened an international conference to provide common definitions and structure to guide current management. There is substantial opportunity for continued research in this disease. In addition to the importance of optimizing the prevention and management of the serious risk of infection, organized evaluations of minimal residual disease and treatment at relapse offer ample opportunities for clinical research. Finally, a scholarly evaluation of quality of life in the increasing number of survivors of this now manageable chronic illness merits further study. The development of consensus guidelines for this disease offers a framework for continued enhancement of the outcome for patients.