Management of hairy cell leukemia variant

Advances in the Treatment of Hairy Cell Leukemia Variant

OPINION STATEMENT

Hairy cell leukemia variant (HCL-V) is a rare B cell lymphoproliferative disorder with a clinical-pathological distinction from the classic form of hairy cell leukemia (HCL-C). HCL-V is more aggressive in nature, has a higher tendency to be refractory to conventional purine analog pharmacotherapies, and leads to a poorer prognosis. Hence, these differing features bring paramount importance to the diagnosis and management of HCL-V. While there is no genetic mutation diagnostic of HCL-V, genetic profiling efforts have identified potential therapeutic targets (i.e., MAP2K1, KDM6A, CREBBP, ARID1A, CCND3, U2AF1, KMT2C) and yielded prognostic markers (i.e., IGHV4-34 rearrangements). To date, combination chemoimmunotherapies, such as cladribine and rituximab, have shown the best results in HCL-V. Future directions include targeted therapies such as moxetumomab pasudotox, ibrutinib, trametinib, and binimetinib and potentially anti-CD22 chimeric antigen receptor T cell therapy. The purpose of this review is to provide an outline of the diagnostic approach and an update on the therapeutic advancements in HCL-V.

Current and Emerging Therapeutic Options for Hairy Cell Leukemia Variant

Hairy cell leukemia variant (HCL-v) is a rare B-cell lymphoproliferative disorder with distinct immunophenotypic and molecular characteristics when compared to classical hairy cell leukemia (HCL-c). In contrast to the enormous progress in therapeutic options for HCL-c, HCL-v remains a therapeutic challenge due to inferior outcomes with standard chemoimmunotherapy and BCR signaling pathway inhibitors, and due to the fact that HCL-v has limited molecular therapeutic targets. In addition, because of the rarity of the disease, there is a paucity of later phase studies or multicenter trials to guide treatment decisions. In this article, we briefly review the diagnostic criteria and clinical characteristics of HCL-v and present a comprehensive overview of current therapeutic options in HCL-v.

Severe Systemic Rash in the Treatment of Hairy Cell Leukemia with Cladribine: Case Report and Literature Review

A 49-year-old male patient who had been diagnosed with variable hairy cell leukemia (HCL-V) was treated with interferon for half a year but exert no obvious effect. After two courses of chemotherapy with cladribine, he achieved remission, and splenomegaly significantly improved (the length in craniocaudal dimension decreased from 15.8cm to 11.8cm). Four years later, the patient got disease relapse and was recommended for another cycle of cladribine (6mg for 7 days). On the last day of cladribine, the patient developed fever with needle-like red rashes on the face, limbs, and trunk. At the very beginning, the rash was lighter in color, sparsely distributed, and without obvious itching. Three days later, the rash gradually darkened, expanded and merged, with itching. With the application of high dose gamma globulin and corticosteroids (prednisolone combined with dexamethasone), the rash finally faded, and the patient was discharged. Rash caused by cladribine is not uncommon, such serious and widespread drug-induced rash is rare, and there are few reports. This article reviewed relevant studies and treatments.

The prevalence of BRAF V600E mutation in hairy cell leukemia: A systematic review and meta-analysis study

Background: BRAF V600E mutations were recently identified in the leukemic cells from patients with hairy cell leukemia (HCL) that this mutation in exon 15 is considered the disease-defining mutation in HCL. Objectives: This meta-analysis aimed to report the prevalence of BRAF V600E mutation in HCL patients. Methods: Three databases including PubMed, Scopus, and Web of Science up to 2017 were searched for the prevalence of BRAF mutation in HCL patients. A random effects meta-analysis was performed using the Comprehensive Meta-Analysis software version 2.0 with the event rate (ER) and 95% confidence interval (95% CI). Results: Out of 552 articles identified from the search, 11 were included included and were analyzed for meta-analysis study. The studies in meta-analysis included 437 patients with HCL, of which 353 (80.8%) patients had BRAF V600E mutation. The pooled ER of the studies was 81.5% (95% CI: 69.5%–89.5%). The Begg's test did not show publication bias, but the Egger's test showed publication bias. Conclusions: With regard to the mentioned limitations, the prevalence of BRAF mutation in HCL patients was >80%. In future studies, considering sex, age, and other variables can exactly show the correlation between these variables with the detection of BRAF mutation.

Differential expression of enhancer of zeste homolog 2 (EZH2) protein in small cell and aggressive B-cell non-Hodgkin lymphomas and differential regulation of EZH2 expression by p-ERK1/2 and MYC in aggressive B-cell lymphomas

EZH2, a member of the polycomb protein group, is an important methyltransferase that is overexpressed in various neoplasms. We found that in small cell B-cell lymphomas, EZH2 is expressed in <40% of neoplastic cells, with heterogenous signal intensity. In aggressive B-cell lymphomas, 70-100% of tumor cells were positive for EZH2 expression with high signal intensity, which correlated with a high proliferation rate. We investigated the potential signaling molecules that regulate EZH2 overexpression in aggressive B-cell lymphomas and found that 80% of cases of EZH2-positive diffuse large B-cell lymphoma show high p-ERK1/2 expression (average ~57% tumor cell positivity). In contrast, only a small percentage of tumor cells (~10%) show p-ERK1/2 expression in Burkitt lymphoma and double hit lymphoma. On average, 91 and 76% of neoplastic cells were positive for MYC expression in Burkitt lymphoma and double hit lymphoma, respectively, while only 20% neoplastic cells were positive for MYC expression in diffuse large B-cell lymphoma. None of the aggressive B-cell lymphomas showed significant p-STAT3 expression in EZH2-overexpressed cases. The correlation of EZH2 expression with aggressive behavior and proliferation rate in B-cell neoplasms suggests that this molecule may function as an oncogenic protein in these neoplasms, with possible regulation by different signaling cascades in different types of aggressive B-cell lymphomas: p-ERK-related signaling in diffuse large B-cell lymphoma, and MYC-related signaling in Burkitt lymphoma and double hit lymphoma. Furthermore, EZH2 and associated signaling cascades may serve as therapeutic targets for the treatment of aggressive B-cell lymphomas.

Hairy cell leukemia: Update on molecular profiling and therapeutic advances

Hairy cell leukemia was initially described as a clinicopathologic entity more than 50 years ago. We have subsequently discovered that HCL is really at least two diseases: classical HCL and the hairy cell leukemia variant. The former is among a small group of cancers exceptional for being (nearly) unified by a single genetic lesion, the BRAF V600E mutation. Over the past three decades, tremendous progress in both diagnostic and prognostic clarification has been accompanied by therapeutic advances in classical HCL. Consequently, this once uniformly fatal disease has been converted in most cases into a chronic illness enabling patients to live long and productive lives. In response to standard therapy, patients have high complete remission rates. Unfortunately, the long-term survival curves have not plateaued, revealing that this disease is controlled but not cured. Though rare and representing only about 10% of an already rare disease, those patients with the variant fare exceptionally poorly with standard therapy: complete response rates to purine nucleoside analogs are reported to be less than 50%, whereas the complete response rates in classical HCL are up to 90%. Novel small molecules targeting BRAF and the B-cell receptor signaling complex, and biologic agents like antibodies and immunotoxin conjugates are being explored for those patients who have relapsed. Substantial opportunities for continued research remain. This complex and multi-faceted disease incorporates challenges from altered immunity associated with the underlying disease and its treatments. Considering the rarity of this malignancy, optimization of patient management requires multi-institutional collaboration. The Hairy Cell Leukemia Foundation (www.hairycellleukemia.org) was formed to coordinate these efforts.