Long-Term Follow-Up of Hairy Cell Leukemia: The Guthrie Clinic Experience Over 25 Years

Background: Hairy cell leukemia (HCL) is an uncommon and indolent leukemia of mature B cells, accounting for 2% of all lymphoid neoplasms. We analyzed characteristics, treatment modalities, response rates, and survival of HCL patients followed at our institution. Methods: We retrospectively reviewed clinical data from the medical records of 56 consecutive HCL patients evaluated in our Hematology/Oncology clinic between 1998 and 2023. Results: The median age at diagnosis was 59 years (range 37–94). Forty-nine patients (87%) were male. First-line therapy was cladribine in 30 patients (54%), cladribine + rituximab in 6 patients (11%), observation in 5 patients (9%), and another modality (fludarabine, pentostatin, single-agent rituximab, or other) in the rest of patients. The median follow-up was 122 months (1–291). The overall response rate was 96%. Complete and partial response rates were 68% and 28%, respectively. Relapses were observed in 45% of patients. The median overall survival was not reached, and the median progression-free survival (PFS) was 181 months (95% CI, 128–252). The 5-year and 10-year PFS were 78% and 29%, respectively. Only 3 patients (5%) died as a result of HCL, either indirectly from immune suppression (pneumonia in 2 patients) or directly (cachexia in 1 patient, untreated because of advanced age and comorbidities). Conclusions: Treatment with purine analogues such as cladribine, plus or minus rituximab, achieves deep and durable responses in most HCL patients. Although relapses were commonly observed, most HCL patients achieved a long-term survival and did not die as a result of HCL.