How is hairy cell leukemia (HCL) treated?

Updated: Sep 16, 2018
  • Author: Emmanuel C Besa, MD; Chief Editor: Koyamangalath Krishnan, MD, FRCP, FACP  more...
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Patients with hairy cell leukemia (HCL) who have stable peripheral blood cell counts may be observed closely on a watch-and-wait program that entails at least quarterly blood cell counts and physical examinations. [22]  Approximately 10% of  patients, usually elderly men with moderate splenomegaly and mild decrease in blood counts, remain asymptomatic and never require therapy.

If the blood cell counts show a sustained decline or the patient becomes symptomatic (ie, develops fatigue or splenomegaly), then therapy with a purine analogue is started before the counts decline to dangerously low levels. Agents used are cladribine (2-chlorodeoxyadenosine [2-CdA]; Leustatin) and pentostatin (2-deoxyformycin [2'-DCF]; Nipent).

Blood cell counts may worsen temporarily after the initiation of either cladribine or pentostatin, so intervention should definitely begin before these hematologic parameters have deteriorated to levels requiring support. Because either of these agents is highly effective as monotherapy, most clinicians select the agent, dose, and schedule that they have effectively used in the past.

The data regarding the use of either pentostatin or cladribine alone for hairy cell leukemia suggest that these agents are equally effective in terms of response rate and remission duration. [9]  Furthermore, the long-term adverse effects are quite comparable. The concerns regarding increased risk for either late infections or secondary malignancies have not been fully resolved.

Substantial improvement in overall survival has been reported with initial use of either agent. Although close monitoring for late adverse effects of therapy is necessary, patients with hairy cell leukemia may now live as long as they would have without this diagnosis. [23] The progress in treatment changed the natural history of this disease. Although the best way to initiate therapy remains unsettled, there is a consensus that attaining a complete remission is important to reduce the possibility of a late relapse.

In selecting appropriate chemotherapy, the following clinical questions must be considered:

  • Is there evidence of active, untreated, ongoing infection?
  • Does the patient have a good performance status and adequate renal function?

Although it is prudent to attempt to treat an active infection before starting purine nucleoside analog therapy in a patient with hairy cell leukemia, the profound neutropenia and monocytopenia from the disease may force the decision to start antileukemic therapy. Otherwise, the patient may succumb to the infection. However, purine analogs may temporarily worsen the hematologic parameters. Most of the initial reports of cladribine indicate that this agent should not be administered to a patient with an ongoing infection. [24, 25]

The use of granulocyte colony-stimulating factor (G-CSF) can raise the absolute neutrophil count and shorten the period of severe neutropenia in hairy cell leukemia patients receiving cladribine, but routine use has not been shown to offer any clinical advantage. [26]

One strategy involves starting treatment with interferon alfa, to obtain an improvement in the granulocyte count that may enable the antibiotic or antifungal therapy to be more effective in controlling the infection; this is followed by a definitive purine analog therapy to achieve complete remission. [27]  Complete remission rates with interferon only are low, at 11% in patients without infection and 5% in patients with infection

Alternatively, pentostatin may be used. Although complete remission rates are better than with interferon—78% in uninfected patients  and 68% in infected patients—and the frequency of febrile episodes requiring antibiotic therapy is 27%, controlling infection if possible before starting pentostatin is recommended.

Pentostatin is cleared by the kidneys, so renal function must be carefully monitored during therapy. Patients with a serum creatinine of 1.5 mg/dL or higher should be excluded from receiving the drug. The initial dose is reduced to 2 mg/m2 in patients whose performance status is impaired, with subsequent escalation to full-dose therapy if tolerated. Hydration with 1.5 L of fluid is usually given along with each dose of the drug and the serum creatinine is checked before each subsequent infusion.

For more information, see Hairy Cell Leukemia Treatment Protocols.

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