Hairy cell leukemia (HCL) and HCL-like disorders have to be distinguished because of their different biology and treatment response. Thus, we conducted a retrospective study on patients with HCL and hairy cell leukemia variant (HCLv) to assess diagnostic algorithms and treatment outcomes in a real-world setting. We analyzed 225 HCL and 26 HCLv patients with median follow-up of 67.9 months (HCL) and 20.1 months (HCLv). Median age at diagnosis was 56.2 (HCL) and 69.5 years (HCLv), male predominance was observed in both groups (76.0% vs. 73.1%). Diagnostics was mostly based on morphological evidence of hairy cells in the peripheral blood and bone marrow. At diagnosis, BRAF V600E mutation was detected in 94.7% of examined HCL patients and in no HCLv patient. Front-line treatment was indicated in 205 (91.1%) HCL and 18 (69.2%) HCLv patients. The majority of HCL patients were administered a cladribine-based regimen (91.2%). Overall response rate (ORR) was higher in cladribine-treated patients compared to those given other treatments (97.7% vs. 81.3%), the same applied with achieving Complete remission (CR) (91.2% vs. 62.5%). HCLv treatment was heterogeneous, but cladribine remained the most frequent option (44.4%) with ORR 81.3% and CR rates 43.8%. Second-line treatment was indicated in 52 HCL and 8 HCLv patients, 25.4% and 44.4% of those treated in first-line. In the whole HCL group, median time to next treatment (TTNT) was not reached and 10-year TTNT was estimated at 74.1%. HCLv patients who underwent first-line treatment had a median TTNT of 56 months. The median overall survival (OS) in HCL patients was not reached compared to HCLv with a median OS of 9.5 years. These data confirm an excellent prognosis for HCL patients treated with cladribine-based therapy. On the contrary, HCLv with its aggressive behavior represents a group of patients in whom novel treatment approaches are needed.

4th Department of Internal Medicine Hematology University Hospital and Charles University Faculty of Medicine Hradec Králové Czech Republic

Central European Institute of Technology Masaryk University Brno Czech Republic

Department of Internal Medicine Hematology and Oncology University Hospital and Masaryk University Brno Czech Republic

Institute of Biostatistics and Analyses Ltd Brno Czech Republic

See more in PubMed

Swerdlow SH, Campo E, Harris NL, et al. WHO Classification of Tumours of Haematopoietic and Lymphoid Tissues. International Agency for Research on Cancer; 2008.

Troussard X, Maitre E, Cornet E. Hairy cell leukemia 2022: update on diagnosis, risk‐stratification, and treatment. Am J Hematol. 2022;97(2):226‐236. https://doi.org/10.1002/ajh.26390

Wörnmann B, Bohn JP, Dietrich S, et al. Hairy‐cell leukemia [online]. In: Onkopedia‐guidelines DGHO; 2022. [Cit. 2. 8. 2023]. Accessed September 20, 2023. https://www.onkopedia-guidelines.info/en/onkopedia/guidelines/hairy-cell-leukemia/@@guideline/html/index.html

Robak T, Matutes E, Catovsky D, Zinzani P, Buske C. Hairy cell leukaemia: ESMO Clinical Practice Guidelines for diagnosis, treatment and follow‐up. Ann Oncol. 2015;26(S5):v100‐v107. https://doi.org/10.1093/annonc/mdv200

Allagio R, Amador C, Anagnostopoulos I, et al. The 5th edition of the world Health organization classification of the haematolymphoid tumours: lymphoid Neoplasms. Leukemia. 2022;36(7):1720‐1748. https://doi.org/10.1038/s41375‐022‐01620‐2

Swerdlow SH, Campo E, Harris NL, et al. WHO Classification of Tumours of Haematopoietic and Lymphoid Tissues, Revised 4th Edition. International Agency for Research on Cancer; 2017.

Campo E, Jaffe ES, Cook JR, et al. The international consensus classification of mature lymphoid Neoplasms: a report from the clinical advisory committee. Blood. 2022;140(11):1229‐1253. https://doi.org/10.1182/blood.2022015851

Madanat YF, Rybicki L, Radivoyevitch T, et al. Long‐term outcomes of hairy cell leukemia treated with purine analogs: a comparison with the general population. Clin Lymphoma, Myeloma & Leukemia. 2017;17(12):857‐862. https://doi.org/10.1016/j.clml.2017.07.003

Saven A, Burian C, Koziol JA, Piro LD. Long‐term follow‐up of patients with hairy cell leukemia after cladribine treatment. Blood. 1998;92(6):1918‐1926. https://doi.org/10.1182/blood.v92.6.1918.418k33_1918_1926

Paillassa J, Cornet E, Noel S, et al. Analysis of a cohort of 279 patients with hairy‐cell leukemia (HCL): 10 years of follow‐up. Blood Cancer J. 2020;10(5):62. https://doi.org/10.1038/s41408‐020‐0328‐z

Dearden CE, Else M, Catovsky D. Long‐term results for pentostatin and cladribine treatment of hairy cell leukemia. Leuk Lymphoma. 2011;52(Suppl pl 2):21‐24. https://doi.org/10.3109/10428194.2011.565093

Catovsky D, Quesada JR, Colomb HM, et al. Consensus resolution: proposed criteria for evaluation of response to treatment in hairy cell leukemia. Leukemia. 2003;1:405.

Jehn U, Bart L, Dietzfelbinger H, Haferlach T, Heinemann V. An update: 12‐year follow up of patients with hairy cell leukemia following treatment with 2‐chlorodeoxyadenosine. Leukemia. 2004;18(9):1476‐1481. https://doi.org/10.1038/sj.leu.2403418

Tiacci E, Trifonov V, Schiavoni G, et al. BRAF mutations in hairy‐cell leukemia. N Engl J Med. 2011;364(24):2305‐2315. https://doi.org/10.1056/nejmoa1014209

Ravandi F, Kreitman RJ, Tiacci E, et al. Consensus opinion from an international group of experts on measurable residual disease in hairy cell leukemia. Blood Cancer J. 2022;12:165. https://doi.org/10.1038/s41408‐022‐00760‐z

Rosenberg JD, Burian C, Waalen J, Saven A. Clinical characteristics and long‐term outcome of young hairy cell leukemia patients treated with cladribine: a single‐institution series. Blood. 2014;123(2):177‐183. https://doi.org/10.1182/blood‐2013‐06‐508754

Burotto M, Stetler‐Stevenson M, Arons E, Zhou H, Wilson W, Kreitman RJ. Bendamustine and rituximab in relapsed and refractory hairy cell leukemia. Clin Cancer Res. 2013;19(22):6313‐6322. https://doi.org/10.1158/1078‐0432.ccr‐13‐1848

Chihara D, Arons E, Stetler‐Stevenson M, et al. Long term follow‐up of a phase II study of cladribine with rituximab with hairy cell leukemia. Blood Adv. 2021;5(23):4807‐4816. https://doi.org/10.1182/bloodadvances.2021005039

Rogers KA, Andritsos LA, Wei L, et al. Phase II study of ibrutinib in classic and variant hairy cell leukemia. Blood. 2021;137(25):3473‐3483. https://doi.org/10.1182/blood.2020009688

Else M, Dearden CE, Matutes E, et al. Long‐term follow‐up of 233 patients with hairy cell leukaemia, treated initially with pentostatin or cladribine, at a median of 16 years from diagnosis. Br J Haematol. 2009;145(6):733‐740. https://doi.org/10.1111/j.1365‐2141.2009.07668.x

Matutes E, Wotherspoon A, Brito‐Babapulle V, Catovsky D. The natural history and clinico‐pathological features of the variant form of hairy cell leukemia. Leukemia. 2001;15(1):184‐186. https://doi.org/10.1038/sj.leu.2401999

Tiacci E, Carolis LD, Simonetti E, et al. Vemurafenib plus rituximab in refractory or relapsed hairy cell leukemia. N Engl J Med. 2021;384(19):1810‐1823. https://doi.org/10.1056/nejmoa2031298