Vemurafenib for BRAF V600-Mutant Erdheim-Chester Disease and Langerhans Cell Histiocytosis: Analysis of Data From the Histology-Independent, Phase 2, Open-label VE-BASKET Study

Designing Clinical Trials for Patients With Rare Cancers: Connecting the Zebras

The field of rare cancer research is rapidly transforming, marked by significant progress in clinical trials and treatment strategies. Rare cancers, as defined by the National Cancer Institute, occur in fewer than 150 cases per million people each year, yet they collectively represent a significant portion of all cancer diagnoses. Because of their infrequency, these cancers pose distinct challenges for clinical trials, including limited patient populations, geographical dispersion, and a general lack of awareness of treatment options. Economic limitations further complicate drug development, making initiatives such as the Orphan Drug Act essential for incentivizing research. The advent of next-generation sequencing (NGS) and precision medicine has been instrumental in identifying actionable genetic alterations in parallel with an explosion in the development of genomically targeted therapies, immunotherapies, and antibody drug conjugates. Advances in clinical NGS, precision medicine, and tumor-agnostic therapies have become central to the progress in rare cancer research. The development and approval of tumor-agnostic drugs, such as BRAF, NTRK, and RET inhibitors, and immunotherapy for mismatch repair deficient/microsatellite instability-high status cancers highlight the potential of personalized treatments across diverse cancer types and across the age spectrum. Collaborative trials from cooperative groups including SWOG DART, ASCO TAPUR, NCI-MATCH, pediatric COG-match, DRUP, IMPRESS, and innovative registrational basket and platform trials (eg, VE-Basket, ROAR, LIBRETTO-001, ARROW), along with patient advocacy group-run trials like TRACK, are enhancing access to clinical trials. In addition, artificial intelligence has the potential to improve the trial matching process. An integrated approach, combining these innovations in collaboration with multiple stakeholders, is crucial for advancing rare cancer research, offering hope for better patient outcomes and quality of life.

High CCR6 expression increases the risk of pediatric Langerhans cell histiocytosis

Langerhans cell histiocytosis (LCH) is a rare disorder that primarily affects children. Considering the intricate clinical presentation of this disease, the identification of specific biomarkers associated with susceptibility to LCH is essential for timely diagnosis and risk stratification. In this study, we examined the skin specimens from pediatric patients with LCH using RNAscope, immunohistochemistry, and sequencing techniques. We observed a notable correlation between elevated CCR6 expression in pathological tissues and LCH risk classification. Therefore, CCR6 expression may serve as an independent predictor of risk in clinical cases of LCH. Furthermore, the frequency of BRAF V600E mutations correlated with risk stratification. We discovered new mutations-H119Y and R108Q-in MAP2K1 in specimens with BRAF V600E mutations. Moreover, CCR6-positive tumors may exhibit an enhanced recruitment of lymphocytes expressing high CCR7 levels.

[68Ga]Ga‑FAPI PET/CT in the evaluation of Langerhans cell histiocytosis: comparison with [18F]FDG PET/CT

PURPOSE

We aimed to explore the value of [68Ga]Ga‑FAPI PET/CT for the evaluation of Langerhans cell histiocytosis (LCH) in comparison with [18F]FDG PET/CT.

METHODS

Thirty-two patients pathologically diagnosed with LCH were enrolled in this study. [68Ga]Ga‑FAPI and [18F]FDG PET/CT were performed within 1 week to identify disease extent and status. The detectability and intensity of the involved organs were compared between these two tracers.

RESULTS

Thirty patients had active disease while two had non-active disease. In patients with active disease, the most commonly involved organ was bone (27/30), and [68Ga]Ga-FAPI PET/CT detected more osseous lesions (106/106) than [18F]FDG PET/CT (52/106). [68Ga]Ga-FAPI also identified liver, skin, and salivary gland involvement, which were often missed by [18F]FDG. Although both tracers detected thymus and pituitary gland involvement, [68Ga]Ga-FAPI demonstrated higher image contrast and more diagnostic confidence. Lymph node involvement, however, was not visualized by [68Ga]Ga-FAPI. Due to the superior sensitivity of [68Ga]Ga-FAPI, approximately 30% (10/30) of patients experienced reclassification in disease status or subtype. Furthermore, [68Ga]Ga‑FAPI appeared to be advantageous in response assessment.

CONCLUSION

[68Ga]Ga-FAPI PET/CT outperforms [18F]FDG PET/CT in detecting osseous and extra-nodal lesions in LCH, providing a valuable tool for precise disease evaluation and treatment planning.

Molecular Pathogenesis of the Histiocytic and Dendritic Cell Neoplasms

The histiocytic and dendritic cell neoplasms encompass a clinically heterogeneous group of disorders leading to tissue damage secondary to the accumulation and infiltration of pathologic cells thought to be derived from the dendritic or monocytic lineages with accompanying inflammation. The pathophysiology of these disorders is poorly understood. Studies over the past 15 y have identified a high-frequency of BRAFV600E, MAP2K1, and other kinase alterations in the histiocytic neoplasms. This review highlights the onslaught of molecular advancements and discusses the impact these insights have had on our understanding of the molecular pathophysiology and therapeutic targets of these rare, enigmatic diseases.

Orbital and ocular adnexal histiocytic tumors; a multidisciplinary literature review

PURPOSE

To review and update the clinical presentation, pathology, treatment strategies, and follow-up of the orbital and ocular adnexal histiocytic tumors.

METHODS

The review included the publications in English literature up to January 2024.

RESULTS

Out of 263 screened publications, 73 studies on Langerhans cell histiocytosis (LCH), juvenile and adult onset xanthogranuloma (JXG, AOXG), Erdheim-Chester disease (ECD), Rosai-Dorfman disease (RDD), and histiocytic sarcoma (HS) were included. Diagnosis is based on histological characteristics and markers on immunohistochemical staining. Treatment options vary depending on the type of histiocytic tumors, number of lesions, number of involved organs, and presence of vital organ involvement such as central nervous system. Surgery is the first diagnostic step for all and serves as the primary treatment for LCH and XG. Systemic chemotherapy is the primary treatment for EDC, RDD, and HS and the treatment of choice for the patients with multifocal or multi-organ involvement as well as recurrent or refractory lesions, regardless of the type of histiocytic tumor. Radiotherapy is an adjunctive primary treatment for the patients with HS. It is reserved for recurrent or refractory lesions in the other types. Targeted therapy is currently in progress and may replace the systemic chemotherapy in patients with LCH, XG, and EDC.

CONCLUSION

Surgical debulking is diagnostic in all and therapeutic in LCH, JXG, and AOXG. All recurrent, refractory, multifocal, and multi-organ tumors require additional systemic chemotherapy with or without radiotherapy. Follow-up imaging every 3 to 6 months for the first 2 years and then annually is recommended.

Temporal bone Langerhans cell histiocytosis with uterine cervix involvement and cutaneous Erdheim-Chester disease

With fewer than 40 documented cases, temporal bone Langerhans cell histiocytosis (LCH) is exceptionally rare in adults. We present a case of temporal bone and uterine cervix LCH in an adult with concurrent cutaneous Erdheim-Chester disease. A woman in her 50s presented with several months of unilateral right aural fullness, otalgia, otorrhoea and tinnitus, unresponsive to antibiotics and aural irrigation. CT of the temporal bone revealed right mastoid destruction, prompting further investigation. Histology obtained from mastoid exploration confirmed LCH. Initial management included radiotherapy, followed by methotrexate and later, cytarabine. Disease monitoring was conducted withPositron Emision Tomography-CT. Due to its rarity, LCH is often initially misdiagnosed. Clinicians should remain vigilant for LCH in patients presenting with unresolved otological symptoms that deviate from the expected clinical course. Swift communication between relevant medical teams is essential for rapid diagnosis and optimal management of potential multisystem LCH when symptoms present in different areas.

Late-Onset Diffuse Xanthomas in an Adult Man

A man in his 60s presented to the hospital with fever, joint pain, and second-degree atrioventricular block. Physical examination revealed diffuse xanthomata, most prominent in the periorbital region. What is your diagnosis?

Genomic Alterations in Langerhans Cell Histiocytosis

Langerhans cell histiocytosis (LCH) is a myeloid neoplastic disorder characterized by inflammatory lesions with clonal histiocytes. LCH is driven by activating mitogen-activated protein kinase (MAPK) pathway mutations. BRAFV600E is the most common mutation and is associated with more extensive disease at presentation and risks of front-line treatment failure, liver disease, and LCH-associated neurodegeneration. Genetic ancestry influences LCH with highest incidence in Hispanic populations. MAPK inhibitors are effective, but do not achieve cure in most cases. Clinical trials prospectively testing risk-stratification based on somatic mutation and/or detectable mutation in peripheral blood may improve outcomes for LCH patients.

New approaches to targeted drug therapy of intracranial tumors

Intracranial tumors encompass a heterogeneous group of neoplasms, including gliomas, meningiomas, pituitary adenomas, schwannomas, craniopharyngiomas, ependymomas, medulloblastomas, and primary central nervous system lymphomas. These tumors present significant challenges due to their diverse molecular characteristics, critical locations, and the unique obstacles posed by the blood-brain barrier (BBB) and blood-tumor barrier (BTB), which limit the efficacy of systemic therapies. Recent advances in molecular biology and genomics have enabled the identification of specific molecular pathways and targets, paving the way for innovative precision therapies. This review examines the current state of targeted therapies for intracranial tumors, including receptor tyrosine kinase (RTK) inhibitors, PI3K/AKT/mTOR inhibitors, RAF/MEK/ERK pathway inhibitors, IDH mutation inhibitors, immune checkpoint inhibitors, and CAR-T cell therapies. Emphasis is placed on the role of the BBB and BTB in modulating drug delivery and therapeutic outcomes. Strategies to overcome these barriers, such as focused ultrasound, nanoparticle-based delivery systems, and convection-enhanced delivery, are also explored. Furthermore, the manuscript reviews clinical trial data, highlighting successes and limitations across different tumor types. It delves into emerging therapeutic approaches, including combination of regimens and personalized treatments based on molecular profiling. By synthesizing the latest research, this article aims to provide a comprehensive understanding of the advancements and ongoing challenges in the targeted treatment of intracranial tumors. The findings underscore the necessity for innovative delivery systems and more extensive clinical trials to optimize therapeutic strategies. This review aspires to inform future research and clinical practices, aiming to improve patient outcomes and quality of life in the management of these complex and life-threatening conditions.

A patient with Eradheim-Chester disease presenting with progressive cystic lung lesions and confirmed pulmonary artery hypertension: a case report

BACKGROUND

Erdheim-Chester disease (ECD), a rare type of non-Langerhans cell histiocytosis, was classified as a haematopoietic tumour by the World Health Organization (WHO) in 2016. It involves multiple systems and is challenging to diagnose due to its broad spectrum of clinical manifestations. The pulmonary manifestations of ECD lack specificity. We present a case of ECD with pronounced cystic lung abnormalities to increase awareness of the disease among pulmonologists and expedite diagnosis and treatment.

CASE PRESENTATION

We report the case of a 44-year-old male who presented with intermittent fever, cough, bilateral leg pain, extensive xanthomas on his face, and extensive pulmonary cystic changes noted on imaging following a pulmonary stab wound incident. Thoracoabdominal enhanced computed tomography (CT) revealed progressive cystic changes in the lungs, notably in the upper lungs and subpleural areas; thickened interlobular septa; circumferential wall thickening of the left subclavian artery; uneven thickening of the aortic wall; and soft tissue shadows in the right atrium of the heart. Bone scintigraphy revealed bilateral symmetric long-bone uptake. Despite his advanced lung abnormalities, he exhibited no hypoxia. Notably, echocardiography indicated severe pulmonary artery hypertension, and right heart catheterization confirmed increased mean pulmonary artery pressure at 37 mmHg and elevated pulmonary vascular resistance. Pathology examination of transbronchial lung biopsy and the facial xanthomas confirmed the presence of ECD-characteristic histiocytes, and genetic testing revealed a BRAF V600E mutation. Treatment with dabrafenib improved respiratory symptoms and facial xanthomas, although some symptoms persisted. Follow-up CT showed reduced interstitial lesions but more pronounced cystic changes.

CONCLUSIONS

This case of ECD illustrates rare pulmonary cystic changes alongside pulmonary arterial hypertension, challenging typical presentations of ECD. This is the first documented instance of pulmonary hypertension associated with ECD, broadening the understanding of its potential complications. These findings emphasize the need for considering ECD in the differential diagnosis of atypical cystic lung lesions, especially when accompanied by systemic symptoms such as xanthomas and bone pain.

An unusual case of multiple primary tumours involving the long bone and oral cavity

PURPOSE OF REVIEW

Multiple primary tumours (MPTs) are a rare clinical entity, and the co-occurrence of synchronous and metachronous MPTs in a single patient is even more exceptional. In the context of Erdheim-Chester Disease (ECD), an already uncommon disorder, the presentation of this disease in the oral cavity is notably rare. Furthermore, the simultaneous presence of ECD in the oral cavity and a Giant Cell Tumour (GCT) in a long bone has not been previously reported in medical literature.

RECENT FINDINGS

This case report presents the first documented instance of such a unique clinical scenario. The marked histological disparities between GCT and ECD further underscore the enigmatic nature of this case. The intricate interplay of genetic, environmental, and pathophysiological factors that led to the simultaneous development of two distinct neoplasms in the same patient is yet to be fully elucidated. This case not only challenges our understanding of the etiology of these conditions but also emphasizes the importance of a multidisciplinary approach to the evaluation and management of such complex cases. The confluence of rare entities, the diagnostic complexities they introduce, and the imperative need for tailored treatment strategies exemplify the intricate landscape of oncological care. This case serves as a compelling reminder of the many unknown facets of disease etiology and the significance of collaborative medical efforts in offering the best possible care for patients confronting exceptionally rare clinical presentations.

Histiocytosis Advancements Parallel Ophthalmic Innovations: The LXXXI Edward Jackson Memorial Lecture

PURPOSE

To highlight innovations in ophthalmic oncology through histiocytosis advancements.

DESIGN

Perspective and retrospective review.

METHODS

The literature outlining the recent advancements in histiocytosis and ocular oncology was reviewed and combined with trial data and personal recollection. Intersections between these two fields were discussed.

RESULTS

The understanding of genetic mutations in disease-both in which cells they occur and the timing of mutation development-has expanded in tandem for the fields of ophthalmic oncology and histiocytosis. Similarly, advancements in diagnostic and treatment technology in one field can help patients in the other. For example, in one study, cell-free DNA testing reliably detected mutations in 14 of 18 (78%) patients with suspected histiocytosis. This technique has also been used in ophthalmic oncology as an alternative to invasive biopsy to avoid the risk of tumor externalization, vision impairment, and other side effects. These and other advancements have allowed both fields to utilize targeted agents to successfully treat diseases with an actionable mutation; or deliver more targeted chemotherapy via the intraarterial technique.

CONCLUSIONS

The explosion of molecular genetics technology and targeted therapies has revolutionized cancer treatment, including histiocytosis and ophthalmic oncology. Recent progress in both fields has shown how these seemingly disparate areas have many intersections, and this speaks to the collaborative spirit that is inherent in clinical research.

Methotrexate and cytarabine in adult LCH: High risk, high reward and maintenance free?

Lin et al. report the long-term follow-up of a phase II trial involving 95 adult patients with Langerhans cell histiocytosis (LCH), investigating the combination of methotrexate and cytarabine (MA). After a median follow-up of 6.5 years, the study showed high response rates, with 90% overall response; 55% of patients free from an event such as disease progression, poor response or death; and 93% of patients were alive, though nearly half experienced febrile neutropenia. This prospective study helps fill gaps in understanding adult LCH treatment, indicating that fixed-duration chemotherapy can yield durable responses despite its associated risks. It emphasizes the importance of personalized treatment decisions, considering both fixed-duration chemotherapy and continuous targeted agents based on patient and disease-specific factors. Commentary on: Lin et al. Long term follow-up of methotrexate and cytarabine in adult patients with Langerhans cell histiocytosis. Br J Haematol 2025; 206:576-584.

Erdheim-Chester disease: Comprehensive insights from genetic mutations to clinical manifestations and therapeutic advances

Erdheim-Chester disease (ECD) is an extremely rare non-Langerhans cell disorder that is believed to include both inflammatory and neoplastic characteristics. It is caused due to genetic mutations in proto-oncogenes like BRAF and MEK, while immunological pathways have an essential role in the onset and progression of the disease. Despite its rarity, ECD poses significant diagnostic and therapeutic challenges due to its heterogeneous clinical presentation and limited understanding of its underlying pathophysiology. Multiple organs can be affected, with the most frequent being long bones, central nervous system and retro-orbital abnormalities, pericardial and myocardial infiltration, interstitial lung disease, retroperitoneal fibrosis, and large blood vessel aberrations. Here, in this review, we comprehensively underline the current knowledge of ECD, including its epidemiology, clinical manifestations, genetics, pathophysiology, diagnostic modalities, and treatment options. By synthesizing existing literature and highlighting areas of ongoing research, this review aims to provide clinicians and researchers with a comprehensive understanding of ECD and guide future directions for improved patient care and outcomes.

Recent advances in therapeutic strategies of Erdheim-Chester disease

Erdheim-Chester disease (ECD) is a rare form of non-LCH characterized by excessive accumulation of histiocytes in various tissues, leading to significant morbidity. The estimated prevalence of ECD is low, with fewer than 1000 cases reported globally, yet it presents considerable clinical challenges due to its heterogeneous manifestations, which include bone pain, cardiovascular complications, and neurological symptoms. Traditional treatment approaches, primarily involving corticosteroids and chemotherapy, have limitations, including inconsistent responses and significant side effects. Recent advances in understanding the pathogenesis of ECD, particularly the role of the BRAF V600E mutation, have led to the exploration of novel therapeutic strategies, such as targeted BRAF inhibitors, MEK and mTOR inhibitors, and other immunotherapies, which offer promise in improving patient outcomes. The review further explores clinical manifestations, and radiographic features of Erdheim-Chester disease, and discusses treatment strategies, current clinical studies in the field of ECD. By integrating these aspects, this review aims to provide a thorough understanding of ECD and its evolving treatment landscape, ultimately contributing to improved patient outcomes.

If it is a solid tumor target, then it may be a hematologic cancer target: Bridging the great divide

Tumor-agnostic US Food and Drug Administration approvals are transforming oncology. They include larotrectinib/entrectinib/repotrectinib (NTRK fusions), selpercatinib (RET fusions), dabrafenib/trametinib (BRAFV600E mutations), pembrolizumab/dostarlimab (microsatellite instability), pembrolizumab (high tumor mutational burden), and trastuzumab deruxtecan (HER2 3+ expression) (all solid cancers). Pemigatinib is approved for FGFR1-rearranged myeloid/lymphoid neoplasms. The genomically driven tissue-agnostic approach has a strong biological rationale (cancer is a disease of the genome), yields remarkably high response rates, and provides drug access to patients with an unmet need (rare/ultra-rare malignancies). Despite the solid tumor focus, both solid and hematologic cancers can harbor identical driver molecular abnormalities and respond to cognate therapies. For example, BRAFV600E and IDH1/2 mutations; ALK, FGFR, and NTRK fusions; PD-L1 amplification; and CD70 antigens are druggable in both solid and blood malignancies by gene-/immune-targeted therapies/chimeric antigen receptor T cells. Future biomarker-based tissue-agnostic basket studies/approvals should bridge the great divide and include both solid and hematologic cancers.

High resolution chest computed tomography responses for a cohort of adult with pulmonary Langerhans cell histiocytosis

Langerhans cell histiocytosis (LCH) is a heterogeneous histiocytosis with various pulmonary manifestations and imaging. We aim to evaluate the pulmonary response of LCH by high resolution chest computed tomography (HRCT) through continuous follow-up.We conducted a retrospective analysis of 73 adult LCH patients with pulmonary involvement. HRCT response was assessed by the change of HRCT global score (nodule score plus cyst score) between the baseline and after therapy. Among them, 69 patients (94.5%) had multi-system LCH with pulmonary involvement. 42 patients received methotrexate and cytarabine regimen, 15 received cytarabine monotherapy, 7 underwent target therapy. 14 (19.2%) achieved complete response (CR) and 45 (61.6%) achieved partial response (PR). The mean global lung-lesion score decreased from 12.2 to 10.6. The mean nodule score decreased from 4.7 to 4.1 and the mean cyst score decreased from 7.4 to 6.5. Overall, 25 (34.2%) exhibited an HRCT response and 3 (4.1%) had HRCT progression, while 45 (61.6%) maintained the same. Among patients with CR or PR, 57.1% and 40.5%, respectively, experienced an HRCT response, whereas no patient with SD or PD had an HRCT response. Multivariable analyses revealed that patients who received low dose cytarabine regimen and those with HRCT score ≥ 10 predicted a shorter PFS. Long Chang, Luo Wang, and Zheng-zheng Liu contributed equally to this work.

Disseminated juvenile xanthogranuloma harbouring a GAB2::BRAF fusion successfully treated with trametinib: a case report

We present an interesting case of disseminated juvenile xanthogranuloma harbouring a GAB2::BRAF fusion that exhibited dramatic response to trametinib, highlighting the utility of RNA sequencing and targeted next-generation sequencing in non-Langerhans cell histiocytosis in identifying potential therapeutic targets.

BRAF V600E mutation and high expression of PD-L1 in Rosai-Dorfman disease: case report and review of the literature

BRAF V600E mutations are frequently found in histiocytic/dendritic cell neoplasms such as Erdheim-Chester disease (ECD) and Langerhans cell histiocytosis (LCH), but few reports have also described BRAF mutations in Rosai-Dorfman disease (RDD), and even these cases may predominantly represent mixed histiocytosis. BRAF mutations have been studied in histiocytic/dendritic cell neoplasms and described to be associated with increased risk of relapse and long-term consequences, but few studies have examined BRAF V600E mutation in RDD, which is recognized as a neoplasm given the high frequency of MAPK pathway alterations. Here, we report a case of BRAF V600E-mutated RDD in a patient who presented with generalized lymphadenopathy. During our evaluation of this patient, we also found expression of PD-L1 in neoplastic histiocytes. During our review period, only few cases of RDD reported to harbor BRAF mutation or were evaluated for the expression of PDL1 by neoplastic cells. Given the potential challenges in distinguishing RDD from other histiocytic/dendritic cell neoplasms, including mixed histiocytosis with similar clinicopathological manifestations, we will discuss the current state of knowledge regarding the frequency and clinical impact of BRAF V600E in RDD, as well as the role of BRAF mutations in RDD pathogenesis. Distinction of BRAF V600E mutated histiocytic/dendritic cell neoplasms requires consideration of distinctive histopathological and immunophenotypic findings in appropriate clinical and radiologic setting. Given the increasing use of BRAF inhibitors as well as checkpoint blockade inhibitors to treat a number of cancers, we will discuss the clinical implications of the presence of BRAF V600E mutation and PD-L1 expression in RDD.

Hairy Kidneys and Sclerotic Bone Lesions

A 72-year-old man with a history of polycythemia vera (positive for JAK2 V617F) presented with several months of functional decline and weight loss. An 18F-fluorodeoxyglucose positron emission tomography/computed tomography showed soft tissue infiltrates and sclerosis of the perirenal spaces with fluorodeoxyglucose uptake. What is your diagnosis?

Efficacy of Combined Encorafenib and Binimetinib Treatment for Erdheim-Chester Disease Harboring Concurrent BRAFV600E and KRASG12R Mutations: A Case Report

BACKGROUND

Erdheim-Chester disease (ECD) is a rare form of non-Langerhans cell histiocytosis with diverse clinical manifestations, often associated with mutations in the mitogen-activated protein kinase/extracellular signal-regulated kinase (MAPK/ERK) pathway. BRAF and KRAS mutations, which are driver mutations of oncogenes, participate in the same signaling pathway (MAPK/ERK pathway) and are usually mutually exclusive. We report a case of ECD with concurrent BRAFV600E and KRASG12R mutations treated using BRAF and MEK inhibitors.

CASE

A 70-year-old man was referred to our hospital with a mesenteric nodal lesion on computed tomography scan. The patient experienced symptoms consistent with ECD, including central diabetes insipidus. Biopsy revealed histiocytes positive for CD68 and CD163, negative for S100, CD1a, and CD21. Liquid-based comprehensive genomic profiling and tissue-based cancer gene panel test identified BRAFV600E and KRASG12R mutations with different variant allele fraction. Additional immunohistochemistry with an antibody specific to mutant BRAFV600E protein stained some proliferating histiocytes, consistent with ECD. Based on the genomic profiling results, we hypothesized that there was a coexistence of a clone harboring BRAFV600E and another clone harboring KRASG12R, and planned a combination therapy with BRAF and MEK inhibitors targeting each clone, respectively. The patient received oral encorafenib at 100 mg once daily and oral binimetinib at 15 mg twice daily. The combination therapy resulted in rapid resolution of symptoms and significant improvement in imaging findings.

CONCLUSION

This case represents a unique presentation of ECD with concurrent BRAFV600E and KRASG12R mutations. Combination therapy with encorafenib and binimetinib targeting each clone resulted in a remarkable therapeutic effect and was well-tolerated. This is the first reported case of ECD treated with encorafenib and binimetinib. The combination therapy with BRAF and MEK inhibitors is one of the rational treatment options for cases of ECD with a suspicion of multiple clones.

Personalized Medicine in Histiocytic Disorders: Novel Targets in Patients Without MAPK Alterations

PURPOSE

BRAF and MEK inhibitors are standard treatments in histiocytic disorders, such as Erdheim-Chester disease (ECD). Some patients lack MAPK-pathway alterations, making these treatments less effective.

METHODS

We describe three patients with histiocytic disorders who have novel non-MAPK pathway alterations. These alterations were studied through genomic and in silico analyses when applicable, then treated with off-label medications rationally selected on the basis of genomic alterations.

RESULTS

Patient 1 had rapidly progressive ECD involving the CNS. A CSF1R in-frame deletion (p.S560_P566del) was identified, and in silico modeling predicted a gain-of-function mutation. This alteration was targeted with pexidartinib, which led to a clinical complete response (CR) within 2 months, and a partial response (PR) on imaging after 3 months. After 15 months, the disease became resistant to pexidartinib and transformed to histiocytic sarcoma. Patient 2 has skin-only involvement of a xanthogranuloma disorder. A KIF5B-FGFR1 fusion was identified on RNA sequencing and targeted with pemigatinib. At 24 months of follow-up, she remains in a clinical PR. Patient 3 has ECD involving the bone marrow, gastrointestinal tract, and subcutaneous tissues. A MEF2C-FLT3 fusion was identified and targeted with sorafenib. He achieved a clinical CR and radiographic PR within 3 months, which has continued for 30 months.

CONCLUSION

We report three patients with histiocytic disorders harboring novel alterations who had sustained responses to off-label kinase inhibitors specific to their histiocytic disorder. Pathogenic variants outside of the MAPK pathway, including variants of unknown significant, may be targeted with readily available small molecules.

Ocular findings in patients with histiocytosis and association with clinical and molecular features

BACKGROUND/AIMS

Ocular manifestations of histiocytosis and their genetic underpinnings are poorly characterised. This study characterises ocular sites of histiocytosis, notate genetic alterations and correlates to histiocytosis clinical features including subtype and sites of disease.

METHODS

Prospective registry-based study of predominantly adult histiocytosis patients at a single-institution tertiary referral centre. 180 eyes of 90 patients (46 males, 44 females) with histiocytosis (Erdheim-Chester disease 34, Rosai-Dorfman 20, xanthogranuloma 7, mixed histiocytosis 13, Langerhans cell histiocytosis (LCH) 15, ALK-positive histiocytosis 1). Ocular findings were categorised by the structure involved. Histiocytosis subtype, sites of disease and genetic status were correlated to ocular findings.

RESULTS

Ocular disease was present in more than half the histiocytosis patient cohort and occurred with other disease sites. Ocular findings were statistically significantly different across histiocytic subtypes with LCH subtypes having the lowest proportion of ocular findings (7%) and all other subtypes having rates of ocular findings which were five times that of patients with LCH (p=0.0009). Of patients with ocular findings, 41% of patients reported ocular symptoms and were significantly more in the group with ocular disease present versus those patients without ocular involvement. The presence of ocular findings was not statistically different by BRAFV600E, MAP2K1 or RAS isoform mutational status.

CONCLUSIONS

Ocular disease is a common feature of histiocytosis with significant visual symptomatology and occurrence in tandem with multisystem sites. Ocular findings vary by histiocytic subtype. The mutational profile of the cohort reflects known mutations in this clinical population, with no specific driver mutation associated with ocular disease.

Precision Oncology Clinical Trials: A Systematic Review of Phase II Clinical Trials with Biomarker-Driven, Adaptive Design

Novel clinical trial designs are conducted in the precision medicine era. This study aimed to evaluate biomarker-driven, adaptive phase II trials in precision oncology, focusing on infrastructure, efficacy, and safety. We systematically reviewed and analyzed the target studies. EMBASE and PubMed searches from 2015 to 2023 generated 29 eligible trials. Data extraction included infrastructure, biomarker screening methodologies, efficacy, and safety profiles. Government agencies, cancer hospitals, and academic societies with accumulated experiences led investigator-initiated precision oncology clinical trials (IIPOCTs), which later guided sponsor-initiated precision oncology clinical trials (SIPOCTs). Most SIPOCTs were international studies with basket design. IIPOCTs primarily used the central laboratory for biomarker screening, but SIPOCTs used both central and local laboratories. Most of the studies adapted next-generation sequencing and/or immunohistochemistry for biomarker screening. Fifteen studies included an independent central review committee for outcome investigation. Efficacy assessments predominantly featured objective response rate as the primary endpoint, with varying results. Nine eligible studies contributed to the United States Food and Drug Administration's marketing authorization. Safety monitoring was rigorous, but reporting formats lacked uniformity. Health-related quality of life and patient-reported outcomes were described in some protocols but rarely reported. Our results reveal that precision oncology trials with adaptive design rapidly and efficiently evaluate anticancer drugs' efficacy and safety, particularly in specified biomarker-driven cohorts. The evolution from IIPOCT to SIPOCT has facilitated fast regulatory approval, providing valuable insights into the precision oncology landscape.

Plasma-Derived Cell-Free DNA for the Diagnosis of Ocular-Involving Histiocytosis

Purpose

Circulating tumor DNA (ctDNA) is released into the plasma by many cancers and offers clinical applications including noninvasive diagnostics. Histiocytosis results from myelogenous clonal expansion of histiocytes, predominantly driven by mutations in the mitogen-activated protein kinase pathway that are potentially detectable by ctDNA-based sequencing assays. However, ocular-involving histiocytosis is often a diagnostic challenge leading to delayed diagnosis and the need for invasive biopsy of sensitive ocular structures. The purpose of this study is to determine whether sequencing of plasma-derived ctDNA can noninvasively diagnose ocular-involving histiocytosis.

Design

Single tertiary cancer referral center.

Participants

Twenty-four adult patients with ocular-involving histiocytosis and ctDNA sequencing.

Methods

Circulating tumor DNA was analyzed (via digital droplet polymerase chain reaction for BRAF V600E, and/or next-generation sequencing) and variant allele frequency was measured at initial presentation to our center. Patient demographics, clinical characteristics, and oncogenic mutations identified from tumor-based sequencing were recorded.

Main Outcome Measures

Plasma-derived ctDNA detectability of pertinent driver mutations of histiocytosis.

Results

At the initial presentation of 14 patients with ocular-involving histiocytosis, sequencing of plasma-derived ctDNA detected driver mutations for histiocytosis (BRAF V600E [10], KRAS [2], ARAF [1], and concurrent MAP2K1/KRAS [1]). Mutations found in circulating cell-free DNA were 100% concordant in 11 of 11 patients with mutations identified by solid tumor sequencing. Of 10 patients without driver mutation detected in ctDNA, 3 patients had alterations (CBL mutation or kinase fusion) not captured in the ctDNA sequencing assay, 3 were wildtype even by tumor sequencing; in 4 patients, tumor-based sequencing identified mutations (BRAF [2], MAP2K1 [2]) not detected in ctDNA. Detectable mutations in ctDNA were significantly more likely in patients with uveal infiltration (P = 0.036).

Conclusions

In this cohort, plasma-derived ctDNA was detectable and diagnostic in the majority of patients with ocular-involving histiocytosis. This suggests that if ocular histiocytosis is suspected (particularly if involving the uvea), noninvasive plasma-derived ctDNA analysis is a helpful diagnostic tool that may obviate the need to invasively biopsy sensitive ocular structures.

Financial Disclosures

Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.

Imaging in Erdheim-Chester Disease

Erdheim-Chester disease (ECD) is a rare, multisystemic, inflammatory, non-Langerhans cell histiocytic neoplasm. The discovery of recurrent and somatic mutations in the mitogen-activated protein kinase signaling pathway, most commonly BRAFV600E, has led to a reclassification of ECD from an inflammatory disorder to a neoplastic process. It is now included in the revised 2016 World Health Organization classification of hematopoietic tumors and in the Langerhans group in the revised 2016 Histiocytosis Classification of the Histiocyte Society. When symptomatic, ECD most commonly manifests with bone pain and fatigue. Also, neurologic manifestations, central diabetes insipidus, exophthalmos, and periorbital xanthelasma-like lesions are frequently encountered. Pathologic findings may vary depending on the site of biopsy and may display a spectrum of features. Thus, due to the diverse clinical presentation and variable histologic findings, imaging can often show the first sign of the disease. Radiologic findings are, however, interpreted in conjunction with clinical and histologic findings to establish the diagnosis of ECD. From providing classic findings that facilitate diagnosis to helping radiologists determine the extent of disease and predicting a prognosis, the role of radiology in ECD has evolved with the understanding of the disease itself. Insights into the molecular pathogenesis and the development of targeted therapeutic agents along with approval of vemurafenib and cobimetinib have necessitated revision of the guidelines for the management of ECD. The authors discuss various radiologic findings of ECD and differential diagnoses by using an organ system-based approach and briefly describe the revised consensus recommendations for evaluation, diagnosis, and treatment based on the International Medical Symposia on ECD from a radiologist's perspective. ©RSNA, 2024 Supplemental material is available for this article. The full digital presentation is available online.

The evolving landscape of tissue-agnostic therapies in precision oncology

Tumor-agnostic therapies represent a paradigm shift in oncology by altering the traditional means of characterizing tumors based on their origin or location. Instead, they zero in on specific genetic anomalies responsible for fueling malignant growth. The watershed moment for tumor-agnostic therapies arrived in 2017, with the US Food and Drug Administration's historic approval of pembrolizumab, an immune checkpoint inhibitor. This milestone marked the marriage of genomics and immunology fields, as an immunotherapeutic agent gained approval based on genomic biomarkers, specifically, microsatellite instability-high or mismatch repair deficiency (dMMR). Subsequently, the approval of NTRK inhibitors, designed to combat NTRK gene fusions prevalent in various tumor types, including pediatric cancers and adult solid tumors, further underscored the potential of tumor-agnostic therapies. The US Food and Drug Administration approvals of targeted therapies (BRAF V600E, RET fusion), immunotherapies (tumor mutational burden ≥10 mutations per megabase, dMMR) and an antibody-drug conjugate (Her2-positive-immunohistochemistry 3+ expression) with pan-cancer efficacy have continued, offering newfound hope to patients grappling with advanced solid tumors that harbor particular biomarkers. In this comprehensive review, the authors delve into the expansive landscape of tissue-agnostic targets and drugs, shedding light on the rationale underpinning this approach, the hurdles it faces, presently approved therapies, voices from the patient advocacy perspective, and the tantalizing prospects on the horizon. This is a welcome advance in oncology that transcends the boundaries of histology and location to provide personalized options.

BRAF-V600E mutations in plasma and peripheral blood mononuclear cells correlate with prognosis of pediatric Langerhans cell histiocytosis treated with first-line therapy

BACKGROUND

The clinical relevance of BRAF-V600E alleles in peripheral blood mononuclear cells (PBMCs) and the prognostic impact of the mutants in cell-free (cf) and PBMC DNAs of Langerhans cell histiocytosis (LCH) have not been fully clarified in pediatric LCH.

METHODS

We retrospectively determined the levels of BRAF-V600E mutation in paired plasma and PBMC samples at the time of diagnosis of LCH. Subsequently, we performed a separate or combined analysis of the clinical and prognostic impact of the mutants.

RESULTS

We assessed BRAF-V600E mutation in peripheral blood from 94 patients of childhood LCH. Our data showed that cfBRAF-V600E was related to young age, multiple-system (MS) disease, involvements of organs with high risk, increased risk of relapse, and worse progression-free survival (PFS) of patients. We also observed that the presence of BRAF-V600E in PBMCs at baseline was significantly associated with MS LCH with risk organ involvement, younger age, and disease progression or relapse. The coexisting of plasma(+)/PBMC(+) identified 36.2% of the patients with the worst outcome, and the hazard ratio was more significant than either of the two alone or neither, indicating that combined analysis of the mutation in plasma and PBMCs was more accurate to predict relapse than evaluation of either one.

CONCLUSIONS

Concurrent assessment of BRAF-V600E mutation in plasma and PBMCs significantly impacted the prognosis of children with LCH. Further prospective studies with larger cohorts need to validate the results of this study.

Current State of Targeted Therapy in Adult Langerhans Cell Histiocytosis and Erdheim-Chester Disease

The mitogen-activated protein kinase (MAPK) pathway is a key driver in many histiocytic disorders, including Langerhans cell histiocytosis (LCH) and Erdheim-Chester disease (ECD). This has led to successful and promising treatment with targeted therapies, including BRAF inhibitors and MEK inhibitors. Additional novel inhibitors have also demonstrated encouraging results. Nevertheless, there are several problems concerning targeted therapy that need to be addressed. These include, among others, incomplete responsiveness and the emergence of resistance to BRAF inhibition as observed in other BRAF-mutant malignancies. Drug resistance and relapse after treatment interruption remain problems with current targeted therapies. Targeted therapy does not seem to eradicate the mutated clone, leading to inevitable relapes, which is a huge challenge for the future. More fundamental research and clinical trials are needed to address these issues and to develop improved targeted therapies that can overcome resistance and achieve long-lasting remissions.

Langerhans cell histiocytosis: NACHO update on progress, chaos, and opportunity on the path to rational cures

Langerhans cell histiocytosis (LCH) is a myeloid neoplastic disorder characterized by lesions with CD1a-positive/Langerin (CD207)-positive histiocytes and inflammatory infiltrate that can cause local tissue damage and systemic inflammation. Clinical presentations range from single lesions with minimal impact to life-threatening disseminated disease. Therapy for systemic LCH has been established through serial trials empirically testing different chemotherapy agents and durations of therapy. However, fewer than 50% of patients who have disseminated disease are cured with the current standard-of-care vinblastine/prednisone/(mercaptopurine), and treatment failure is associated with long-term morbidity, including the risk of LCH-associated neurodegeneration. Historically, the nature of LCH-whether a reactive condition versus a neoplastic/malignant condition-was uncertain. Over the past 15 years, seminal discoveries have broadly defined LCH pathogenesis; specifically, activating mitogen-activated protein kinase pathway mutations (most frequently, BRAFV600E) in myeloid precursors drive lesion formation. LCH therefore is a clonal neoplastic disorder, although secondary inflammatory features contribute to the disease. These paradigm-changing insights offer a promise of rational cures for patients based on individual mutations, clonal reservoirs, and extent of disease. However, the pace of clinical trial development behind lags the kinetics of translational discovery. In this review, the authors discuss the current understanding of LCH biology, clinical characteristics, therapeutic strategies, and opportunities to improve outcomes for every patient through coordinated agent prioritization and clinical trial efforts.

Selected Case From the Arkadi M. Rywlin International Pathology Slide Seminar: Involvement of Skin and Soft Tissue by Erdheim-Chester Disease

Erdheim-Chester disease is a rare form of non-Langerhans cell histiocytosis that preferentially involves long bones but can affect a variety of other organs. Initial presentation with extraskeletal involvement is not unusual and is most commonly observed in the central nervous system, heart, retroperitoneum, lungs, and skin. Initial presentation of the disease as a subcutaneous soft tissue mass is exceedingly rare and may pose difficulties for diagnosis. We describe a case of Erdheim-Chester disease that initially presented as a cutaneous and subcutaneous soft tissue mass in the right posterior shoulder of a 52-year-old man.

Histiocytosis and adult-onset orbital xanthogranuloma in 2023: a review of the literature and mini case series

PURPOSE

Within the large umbrella of histiocytosis are a few similar yet heterogenous entities involving the orbit and periocular tissues with or without systemic infiltration, termed adult onset xanthogranuloma or orbital xanthogranuloma. Due to rarity of these conditions, different classifications in use, diverse clinical presentations and still unknown etiology, the aim of this paper was to provide an up-to-date literature review of the actual understanding of histiocytosis and its subgroups involving the orbit and periocular area, diagnostic strategies and therapeutic modalities.

METHODS

We present a review of literature and small case series comprising four patients diagnosed and treated in the period from 2001 until 2023 in our hospital. Clinical files of 4 patients with adult-onset xanthogranulomatous disease of the orbit and ocular adnexa (AOXGD) were reviewed retrospectively. Clinical, laboratory, radiological, histopathological, and immunohistochemical findings were reexamined.

RESULTS

Reviewing medical records of our patients with AOXGD, we found significant overlap between histiocytosis and different immune disorders. A broad workup should be considered in these patients as they can harbour severe immune disfunctions and hematologic disorders. Preferred treatment modality depends on a histopathologic type of AOXGD, clinical presentation and systemic involvement and should be conducted multidisciplinary.

CONCLUSION

The diagnosis is often delayed because of its rarity and diverse clinical findings. Development of molecular genetic tests, detection of BRAF V600E mutation and different types of kinase mutations, mutations in transcriptional regulatory genes as well as tyrosine kinase receptors have shed a new light on the etiopathogenesis and potential targeted treatment of histiocytosis.

Langerhans cell histiocytosis in sphenoid sinus with vision impairment: Case report and literature review

Langerhans cell histiocytosis (LCH) is a neoplastic disease characterized by aberrant proliferation of the mononuclear phagocyte system, predominantly affecting children under the age of 3 years. Although LCH can affect almost all organs, sinus involvement is rare. This case report documents a 9-year-old boy presented with vision impairment and intermittent headache on the right side. The CT scan and MRI examination revealed the presence of a soft mass in the right atrium of sphenoid sinus, which impacted the right optic canal. Biopsy results confirmed the presence of LCH. Considering the involvement of optic canal and vision impairment, meticulous debridement was performed followed by a 12-month standard chemotherapy. After 2 years of follow-up, the patient showed significant improvement, despite the presence of an encapsulated cyst in the right sphenoid sinus. This case highlights the importance of considering LCH when encountering an isolated soft mass accompanied by decreased vision in the sphenoid sinus. A thorough physical examination, laboratory tests, and imaging methods should be performed, with a biopsy being necessary to confirm the type of lesion and guide the appropriate treatment.

Orbital histiocytosis; From A to Z

PURPOSE

Histiocytosis is one of the most challenging diseases in medical practice. Because of the broad spectrum of clinical manifestations, systemic involvements, unknown etiology, and complex management, different types of histiocytosis are still a big question mark for us. Orbital histiocytosis is characterized by the abnormal proliferation of histiocytes in orbital tissues. It could affect the orbit, eyelid, conjunctiva, and uveal tract. Orbital histiocytosis can cause limited eye movement, proptosis, decreased visual acuity, and epiphora. In this study, we review the novel findings regarding the pathophysiology, diagnosis, and treatment of different types of histiocytosis, focusing on their orbital manifestations.

METHOD

This review was performed based on a search of the PubMed, Scopus, and Embase databases or relevant published papers regarding orbital histiocytosis on October 9th, 2023. No time restriction was proposed, and articles were excluded if they were not referenced in English.

RESULTS

391 articles were screened, most of them being case reports. The pathophysiology of histiocytosis is still unclear. However, different mutations are found to be prevalent in most of the patients. The diagnostic path can be different based on various factors such as age, lesion site, type of histiocytosis, and the stage of the disease. Some modalities, such as corticosteroids and surgery, are used widely for treatment. On the other hand, based on some specific etiological factors for each type, alternative treatments have been proposed.

CONCLUSION

Significant progress has been made in the detection of somatic molecular changes. Many case studies describe various disease patterns influencing the biological perspectives on different types of histiocytosis. It is necessary to continue investigating and clustering data from a broad range of patients with histiocytosis in children and adults to define the best ways to diagnose and treat these patients.

Patterns and organ treatment response of Erdheim-Chester disease with cardiac involvement

OBJECTIVE

To evaluate the heart response of Erdheim-Chester disease (ECD) through continuous follow-up within our large cohort, for which there is a lack of understanding.

METHODS

We conducted a retrospective analysis of clinical data from patients with ECD with cardiac involvement diagnosed at our centre between January 2010 and August 2023. We assessed the heart response by integrating pericardial effusion and metabolic responses.

RESULTS

A total of 40 patients were included, with a median age of 51.5 years (range: 29-66) and a BRAFV600E mutation rate of 56%. The most common imaging manifestations observed were pericardial effusion (73%), right atrium (70%) and right atrioventricular sulcus infiltration (58%). Among 21 evaluable patients, 18 (86%) achieved a heart response including 5 (24%) complete response (CR) and 13 (62%) partial response (PR). The CR rate of pericardial effusion response was 33%, while the PR rate was 56%. Regarding the cardiac mass response, 33% of patients showed PR. For cardiac metabolic response, 32% and 53% of patients achieved complete and partial metabolic response, respectively. There was a correlation between pericardial effusion response and cardiac metabolic response (r=0.73 (95% CI 0.12 to 0.83), p<0.001). The median follow-up was 50.2 months (range: 1.0-102.8 months). The estimated 5-year overall survival was 78.9%. The median progression-free survival was 59.4 months (95% CI 26.2 to 92.7 months). Patients who received BRAF inhibitors achieved better heart response (p=0.037) regardless of treatment lines.

CONCLUSION

We pioneered the evaluation of heart response of ECD considering both pericardial effusion and cardiac metabolic response within our cohort, revealing a correlation between these two indicators. BRAF inhibitors may improve heart response, regardless of the treatment lines.

Advances in our understanding of genetic markers and targeted therapies for pediatric LCH

INTRODUCTION

Langerhans cell histiocytosis (LCH) is a rare myeloid neoplasm, encompassing a diverse clinical spectrum ranging from localized bone or skin lesions to a multisystemic life-threatening condition. Over the past decade, there has been an expansion in understanding the molecular biology of LCH, which translated into innovative targeted therapeutic approaches.

AREAS COVERED

In this article, we will review the molecular alterations observed in pediatric LCH and the relationship between these molecular changes and the clinical phenotype, as well as targeted therapies in LCH.

EXPERT OPINION

Mitogen-activated protein kinase (MAPK) pathway mutation is a hallmark of LCH and is identified in 80% of the cases. Notably, BRAFV600E mutation is seen in ~50-60% of the cases, ~30% has other MAPK pathway mutations, while 15-20% have no detected mutations. While the first line therapeutic approach is vinblastine and prednisone, targeted therapies - specifically BRAF/MEK inhibitors - emerged as a promising second-line salvage strategy, particularly when a mutation is identified. Most patients respond to BRAF/MEK inhibitors but at least 75% reactivate after stopping, however, most patients respond again when restarting inhibitors.

The plasma-soluble CSF1R level is a promising prognostic indicator for pediatric Langerhans cell histiocytosis

Langerhans cell histiocytosis (LCH) is a rare hematologic neoplasm characterized by the clonal proliferation of Langerhans-like cells. Colony-stimulating factor 1 receptor (CSF1R) is a membrane-bound receptor that is highly expressed in LCH cells and tumor-associated macrophages. In this study, a soluble form of CSF1R protein (sCSF1R) was identified by plasma proteome profiling, and its role in evaluating LCH prognosis was explored. We prospectively measured plasma sCSF1R levels in 104 LCH patients and 10 healthy children using ELISA. Plasma sCSF1R levels were greater in LCH patients than in healthy controls (p < .001) and significantly differed among the three disease extents, with the highest level in MS RO+ LCH patients (p < .001). Accordingly, immunofluorescence showed the highest level of membrane-bound CSF1R in MS RO+ patients. Furthermore, the plasma sCSF1R concentration at diagnosis could efficiently predict the prognosis of LCH patients treated with standard first-line treatment (AUC = 0.782, p < .001). Notably, dynamic monitoring of sCSF1R levels could predict relapse early in patients receiving BRAF inhibitor treatment. In vitro drug sensitivity data showed that sCSF1R increased resistance to Ara-C in THP-1 cells expressing ectopic BRAF-V600E. Overall, the plasma sCSF1R level at diagnosis and during follow-up is of great clinical importance in pediatric LCH patients.

Clofarabine monotherapy in aggressive, relapsed and refractory Langerhans cell histiocytosis

Over 50% of patients with systemic LCH are not cured with front-line therapies, and data to guide salvage options are limited. We describe 58 patients with LCH who were treated with clofarabine. Clofarabine monotherapy was active against LCH in this cohort, including heavily pretreated patients with a systemic objective response rate of 92.6%, higher in children (93.8%) than adults (83.3%). BRAFV600E+ variant allele frequency in peripheral blood is correlated with clinical responses. Prospective multicentre trials are warranted to determine optimal dosing, long-term efficacy, late toxicities, relative cost and patient-reported outcomes of clofarabine compared to alternative LCH salvage therapy strategies.

Clinical, radiological and molecular responses to combination chemotherapy with MAPK pathway inhibition in relapsed and refractory Langerhans cell histiocytosis

Optimal therapeutic approaches for advanced Langerhans cell histiocytosis (LCH) are not known. We assessed the safety and efficacy of combined chemotherapy with MAPK pathway inhibition in 10 patients with refractory systemic disease and/or LCH-associated neurodegeneration. Overall response rate was 9/10 (90%) for the entire cohort: 5/5 (100%) for patients with systemic disease and 6/7 (86%) for patients with central nervous system disease. BRAFV600E+ peripheral blood fraction decreased in 5/6 (83%). Toxicities included fever, skin rash, myalgias, neuropathy, cytopenias and hypocalcaemia. Prospective trials are required to optimize combination strategies, determine potential to achieve cure and compare outcomes to chemotherapy or MAPK inhibitor monotherapy.

Erdheim-Chester disease as complex clinical presentation and diagnosis: A case report and concise review of literature

RATIONALE

Erdheim-Chester disease (ECD) is a rare multisystemic disease characterized by the infiltration of multiple organs by foamy CD68 + CD1a-histiocytes. The genetic background consists of gain-of-function somatic mutations in the mitogen-activated protein kinase pathway. The purpose of the present paper is to make a contribution to the scientific literature on ECD by reporting our experience with a complex clinical case report, along with a concise review of the literature. We discussed the unusual clinical presentation, the complex diagnostic process and the comparison with other published cases.

PATIENT CONCERNS

A 70-year-old man presented with arthralgia due to multiple bone areas of sclerosis, first diagnosed with metastases of a prostatic neoplasm. Sequential thorax-abdomen, femoral and homer contrast-enhanced computed tomography (CT) showed pericardial effusion, pulmonary fibrosis, and perirenal fibrous tissue as "hairy kidneys." He underwent. Three bone biopsies were unsuccessful to reach diagnosis.

DIAGNOSES

A xanthelasma biopsy showed histopathological signs compatible with ECD; genetic analysis showed the mutation BRAFV600E.

INTERVENTIONS

The patient underwent targeted therapy with vemurafenib (BRAF-inhibitor), discontinued 2 weeks later due to the onset of a diffuse erythematous papular rash on the trunk and limbs.

OUTCOMES

At the 1-year follow-up, there was only progression of chronic kidney disease (CKD).

LESSONS

The present case report describes how ECD diagnosis could represent a challenge for clinicians, owing to its heterogeneous clinical presentation. Early diagnosis followed by prompt therapy is essential for modifying the natural history of the disease.

Phase 2 study using low dose cytarabine for adult patients with newly diagnosed Langerhans cell histiocytosis

Langerhans cell histiocytosis (LCH) lacks a standardized first-line therapy. This single-center, phase 2 prospective study (NCT04121819) enrolled 61 newly diagnosed adult LCH patients with multisystem or multifocal single system disease from October 2019 to June 2022. Subcutaneous cytarabine (100 mg/m2 for 5 days) was administered in 35-day cycles for 12 total cycles. The primary endpoint was event-free survival (EFS). The median age was 33 years (range 18-66). Twelve patients (19.7%) had liver involvement, of which 2 also had spleen involvement. Among 43 patients undergoing next-generation sequencing, BRAF alterations (44.2%) were most frequent, followed by TP53 (16.3%), MAP2K1 (14.0%) and IDH2 (11.6%). MAPK pathway alterations occurred in 28 patients (65.1%). The overall response rate was 93.4%, with 20 (32.7%) achieving complete response and 37 (60.7%) partial response. After a median 30 months follow-up, 21 (34.4%) relapsed without deaths. Estimated 3-year OS and EFS were 100.0% and 58.5%, respectively. Multivariate analysis identified ≥3 involved organs (P = 0.007; HR 3.937, 95% CI: 1.456-9.804) and baseline lung involvement (P = 0.028; HR 2.976, 95% CI: 1.126-7.874) as poor prognostic factors for EFS. The most common grade 3-4 toxicities were neutropenia (27.9%), thrombocytopenia (1.6%), and nausea (1.6%). In conclusion, cytarabine monotherapy is an effective and safe regimen for newly diagnosed adults, while baseline lung or ≥3 involved organs confers poor prognosis.

Dabrafenib and trametinib in Langerhans cell histiocytosis and other histiocytic disorders

The standard treatment for Langerhans cell histiocytosis (LCH) is chemotherapy, although the failure rates are high. Since MAP-kinase activating mutations are found in most cases, BRAF- and MEK-inhibitors have been used successfully to treat patients with refractory or relapsed disease. However, data on long-term responses in children are limited and there are no data on the use of these inhibitors as first-line therapy. We treated 34 patients (26 with LCH, 2 with juvenile xanthogranuloma, 2 with Rosai-Dorfman disease, and 4 with presumed single site-central nervous system histiocytosis) with dabrafenib and/or trametinib, either as first line or after relapse or failure of chemotherapy. Sixteen patients, aged 1.3-21 years, had disease that was recurrent or refractory to chemotherapy, nine of whom had multisystem LCH with risk-organ involvement. With a median treatment duration of 4.3 years, 15 (94%) patients have sustained favorable responses. Eighteen patients, aged 0.2-45 years, received an inhibitor as first-line treatment. All of these have had sustained favorable responses, with a median treatment duration of 2.5 years. Three patients with presumed isolated central nervous system/pituitary stalk histiocytosis had stabilization or improvement of their disease. Overall, inhibitors were well tolerated. Five patients with single-system LCH discontinued therapy and remain off therapy without recurrence. In contrast, all four patients with multisystem disease who discontinued therapy had to restart treatment. Our data suggest that children suffering from histiocytoses can be treated safely and effectively with dabrafenib or trametinib. Additional studies are, however, needed to determine the long-term safety and optimal duration of therapy.