Patients with hairy cell leukemia (HCL) treated with cladribine have an estimated 15-year overall survival rate of more than 80%, though patients who reach a complete response (CR) during treatment are likely to have the highest long-term survival rates, according to research published in Blood Cancer Journal.

HCL, a rare lymphoproliferative disease, is known to have several morphological and molecular features that render it susceptible to specific treatments. Cladribine, which was introduced in his patient population in the 1990s, greatly improved outcomes among patients with HCL, regardless of mode of administration.

Although 1 dose of cladribine may induce a response, relapses have been noted during follow-up. Infections, furthermore, are a known event that occur after treatment, and require monitoring and, sometimes, long-term care. For this multicenter study, researchers aimed to establish long-term survival and morbidity rates among patients with HCL treated with cladribine.

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Overall, data from 513 patients were included. In the overall cohort, 81.9% of patients were male sex, the median age was 54 years, and 84.9% of patients had an Eastern Cooperative Oncology Group performance status of 0; 330 and 183 patients received cladribine intravenously and subcutaneously, respectively.

The median follow-up was 6.83 years. Analysis showed that the overall response rate was 91.8%; 65.3%, 18.7%, 7.8%, and 8.2% of patients had a CR, a partial response (PR), a hematologic response, and no response, respectively. Univariate analysis suggested that hemoglobin value, number of circulating hairy cells, recovery of absolute neutrophil count, and spleen normalization were each associated with reaching a CR, compared with a PR (all P <.05).

At follow-up, the median time to relapse was determined to be 12.2 years. Patients who reached a CR, however, were more likely to have a longer response duration (19.4 years vs 4.8 years with a PR; P <.0001). At 5, 10, and 15 years, furthermore, the median OS rates were estimated to be 95.3%, 92.4%, and 81.8%, respectively.

Non-hematologic grade 3 or worse adverse events were noted in 20.1% of patients, and 9.5% of patients died overall; 2.7% of patients died because of an infection. Progression of HCL accounted for death in 0.4% of patients.

“These data will probably change the therapeutic approach to HCL: in the next future, incorporation of newer agents will be useful to further improve the long-term outcome of these patients,” the authors wrote. “At present, [cladribine] still remains the backbone of treatment in this setting of patients.”


Pagano L, Criscuolo M, Broccoli A, et al. Long-term follow-up of cladribine treatment in hairy cell leukemia: 30-year experience in a multicentric Italian study. Blood Cancer J. 2022;12(7):109. doi:10.1038/s41408-022-00702-9