Consensus opinion from an international group of experts on measurable residual disease in hairy cell leukemia

Early clearance of hairy cell leukaemia in the bone marrow after first-line treatment with cladribine predicts a favourable outcome

First-line purine nucleoside analogues (PNAs) in hairy cell leukaemia (HCL) allow deep and long-lasting responses. We retrospectively analysed 53 HCL patients treated frontline with cladribine and assessed for response at 2 and 6 months after treatment to evaluate the kinetics of response. The estimated median progression-free survival was significantly different according to the degree of residual HCL infiltrate detected by immunohistochemistry at the bone marrow biopsy at 2 months (≤5% vs. >5%, 247 vs. 132 months, respectively, p = 0.033), but not at 6 months (p = 0.79). Our data suggest a favourable prognostic impact of early marrow HCL clearance in patients treated with cladribine.

A Case of Hairy Cell Leukemia Variant: Literature Analysis With Focus on Unmet Needs

Hairy cell leukemia variant (HCLv) is a sporadic, B-cell non-Hodgkin lymphoma classified under chronic lymphoproliferative disorders. HCLv usually presents with easy fatigue, dragging pain abdomen, anemia, splenomegaly, hepatomegaly, initially leukocytosis followed by leucopenia, hairy cells in the smear and bone marrow, and an increased risk of infections. There is hypercellular bone marrow, and cytopenias are secondary to hypersplenism. It is essential to differentiate HCL from disorders like classic hairy cell leukemia (HCLc), splenic marginal zone lymphoma, and splenic diffuse red pulp lymphoma, as these are biologically different, with divergent approaches and outcomes. HCLv is poorly responsive or primary refractory to standard purine analogs cladribine or pentostatin. It has lower response rates to even cladribine and rituximab combination, a standard of care for classic HCL with very good response rates. Here, we present a case of an elderly male who presented with splenomegaly and leukocytosis, diagnosed as HCLv, and was treated with a cladribine and rituximab-based regime but showed residual cells in bone marrow on flow cytometry at six months post-treatment. There were no residual cells in peripheral blood in flow cytometry. Various aspects of the disease are discussed here with a detailed literature analysis. There is a definite unmet need for research on better treatment options in HCLv to improve its overall outcome.

Hairy Cell Leukemia: Where Are We in 2023?

PURPOSE OF REVIEW

This article summarizes the current state of knowledge of hairy cell leukemia (HCL) regarding presentation, diagnosis, therapy, and monitoring, including perspectives on emergent therapies.

RECENT FINDINGS

Over the past decade, there has been enormous progress in the understanding of the biology of HCL which has led to the development of novel therapeutic strategies. The maturation of data regarding existing management strategies has also lent considerable insight into therapeutic outcomes and prognosis of patients treated with chemo- or chemoimmunotherapy. Purine nucleoside analogs remain the cornerstone of treatment, and the addition of rituximab has deepened and prolonged responses in the upfront and relapsed setting. Targeted therapies now have a more defined role in the management of HCL, with BRAF inhibitors now having a potential in the first-line setting in selected cases as well as in relapse. Next-generation sequencing for the identification of targetable mutations, evaluation of measurable residual disease, and risk stratification continue to be areas of active investigation. Recent advances in HCL have led to more effective therapeutics in the upfront and relapsed setting. Future efforts will focus on identifying patients with high-risk disease who require intensified regimens. Multicenter collaborations are the key to improving overall survival and quality of life in this rare disease.

Refractory and relapsed hairy-cell leukemia (HCL): casting light on promising experimental drugs in clinical trials

INTRODUCTION

Hairy cell leukemia (HCL) is a rare subtype of indolent lymphoid leukemia originating from a mature B lymphocyte. The standard first-line treatment for classic HCL, and HCL variant (HCLv), consists of purine nucleoside analogs (PNA), with or without rituximab. However, almost half of patients relapse and require subsequent therapy.

AREAS COVERED

This article summarizes recent achievements in the treatment of relapsed and refractory HCL. A literature search was conducted of the PubMed and MEDLINE database for articles in English. Publications from 2010 through January 2023 were scrutinized. The search terms used were hairy cell leukemia in conjunction with BRAF inhibitors, Bruton's tyrosine kinase (BTK) inhibitors, CD20 monoclonal antibodies, relapsed, refractory and variant.The growing understanding of HCL biology has allowed the design of several new, chemotherapy-free targeted drugs which have demonstrated encouraging efficacy in early clinical trials.

EXPERT OPINION

Novel drugs will soon be available to assist standard therapy for HCL and HCLv among patients with suboptimal results following PNA treatment. In particular, the BRAF inhibitors vemurafenib and dabrafenib, with or without rituximab, have revolutionized treatment of patients with relapsed or refractory disease.