Consensus disease definitions for neurologic immune-related adverse events of immune checkpoint inhibitors

Immune checkpoint inhibitor-related CNS vasculitis - A systematic review and report of 6 cases

BACKGROUND

Immune checkpoint inhibitors (ICI) represent an important new class of immunotherapy used in cancer treatment. Though effective, immune-related adverse events (irAE) are reported, including cerebral vasculitis (nirVasculitis). In this systematic review, we aim to identify clinical and laboratory features of nirVasculitis and exemplify these in six local clinical cases.

OBSERVATIONS

We followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Two independent researchers searched, identified, and extracted data from both PubMed and Embase to identify reports on nirVasculitis. Based on current criteria for diagnostic certainty patients were categorized as having definite, probable, or possible nirVasculitis. 20 cases described relevant symptomatology and met our inclusion criteria. Non-small-cell lung cancer (55 %) was the most frequent cancer type. Most cases (95 %) received a programmed death-1 (PD-1) inhibitor. One patient had definite vasculitis, seven probable vasculitis, and twelve possible vasculitis. Signs and symptoms included aphasia (n = 5), loss of consciousness (n = 7), confusion (n = 8), unilateral sensory or motor dysfunction (n = 5), and fever or headache (n = 9). All patients had brain imaging and seventeen underwent a lumbar puncture. Of these, 64.7 % had pleocytosis and 52.9 % elevated protein in cerebrospinal fluid. Nineteen patients received corticosteroids. Eight patients fully or partially recovered. Eight patients died due to nirVasculitis, three to advanced cancer, and one lost to follow-up.

CONCLUSIONS

There are few clinical reports of nirVasculitis which may be due to underreporting or rarity of complications. Guidelines for diagnostics and reporting may improve awareness and early recognition to initiate important immunosuppressive treatment.

The pathogenesis of neurological immune-related adverse events following immune checkpoint inhibitor therapy

Cancer is a leading cause of morbidity and mortality worldwide. The development of immune checkpoint inhibitors (ICI) has revolutionised cancer therapy, and patients who were previously incurable can now have excellent responses. These therapies work by blocking inhibitory immune pathways, like cytotoxic T lymphocyte-associated protein 4 (CTLA-4), programmed cell death-1 (PD-1), its ligand PD-L1, and lymphocyte activation gene 3 (LAG-3); which leads to increased anti-tumour immune responses. However, their use can lead to the development of immune-related adverse events (irAEs), which may result in severe disability, interruption of cancer therapy, and even death. Neurological autoimmune sequelae occur in 1-10 % of patients treated with ICIs and can be fatal. They encompass a broad spectrum of diseases, may affect the central and the peripheral nervous system, and include syndromes like encephalitis, cerebellitis, neuropathy, and myositis. In some cases, neurological irAEs can be associated with autoantibodies recognising neuronal or glial targets. In this review, we first describe the key targets in ICI therapy, followed by a formulation of irAEs and their clinical presentations, where we focus on neurological syndromes. We comprehensively formulate the current literature evaluating cell surface and intracellular autoantibodies, cytokines, chemokines, leukocyte patterns, other blood derived biomarkers, and immunogenetic profiles; and highlight their impact on our understanding of the pathogenesis of neurological irAEs. Finally, we describe therapeutic pathways and patient outcomes, and provide an overview on future aspects of ICI cancer therapy.

Consensus disease definitions for ophthalmic immune-related adverse events of immune checkpoint inhibitors

Ophthalmic immune-related adverse events (Eye-irAEs) from immune checkpoint inhibitors can cause visual morbidity. The absence of standardized definitions for Eye-irAEs not only impedes the development of evidence-based treatments but also progress in translational research. The objective of this study was to develop consensus guidance for an approach to Eye-irAEs.Four ophthalmic physicians (uveitis specialists and neuro-ophthalmologists) drafted Eye-irAE consensus guidance and definitions, which were reviewed by the multidisciplinary Eye-irAE definition panel. The panel was divided into Group A (Neuro-ophthalmology/Orbital Disease) and Group B (Uveitis/Ocular Surface Disease). A modified Delphi consensus process was used, with two rounds of anonymous ratings by panelists and two meetings to discuss areas of controversy. For each disorder, five diagnostic components were evaluated: symptoms, examination findings, laboratory studies/imaging findings, diagnostic criteria, and treatment. Panelists rated content for usability, appropriateness and accuracy on 9-point scales in electronic surveys and provided free-text comments. Aggregated survey responses were incorporated into revised definitions. Consensus was based on numeric ratings using the RAND Corporation/ University of California Los Angeles Health Services Utilization Study (RAND/UCLA) Appropriateness Method with prespecified definitions.29 panelists from 25 academic medical centers voted on 114 rating scales (66 neuro-ophthalmic/orbital disease components, 48 uveitis/ocular surface disease components); of these, 86.3% (57/66) in Group A and 89.6% (43/48) in Group B reached first-round consensus. After revisions, all items except 6.1% (4/66) in Group A and 1.6% (1/60) in Group B received second-round consensus. Consensus definitions were achieved for 10/11 neuro-ophthalmic/orbital disorders: optic neuritis, inflammatory optic disc edema, arteritic ischemic optic neuropathy, optic perineuritis, orbital inflammation, thyroid eye disease-like orbital inflammation, cavernous sinus syndrome, oculomotor mononeuritis, trochlear mononeuritis, and abducens mononeuritis. Consensus definitions were achieved for 9/10 uveitis/ocular surface disorders: anterior uveitis, intermediate uveitis, posterior uveitis, panuveitis, Vogt-Koyanagi-Harada-like syndrome, sarcoidosis-like syndrome, acute macular neuroretinopathy, dry eye disease, and scleritis.These disease definitions establish a standardized classification for Eye-irAE, highlighting differences between irAEs and other inflammatory disorders. Importantly, diagnostic certainty does not always align directly with the need to treat as an Eye-irAE. Given the consensus from this representative panel group, it is anticipated the definitions will be used broadly across clinical and research settings.

Case Report: Successful immune checkpoint inhibitor rechallenge after sintilimab-induced Guillain-Barré syndrome

Immune checkpoint inhibitors (ICIs) have revolutionized hepatocellular carcinoma (HCC) treatment, while immune-related adverse events (IRAEs) pose significant challenges. We report a 60-year-old male with unresectable HCC who developed Guillain-Barré syndrome (GBS), a rare but severe neurologic complication, after three cycles of sintilimab plus bevacizumab biosimilar and conventional transarterial chemoembolization (c-TACE). The patient presented with progressive ascending weakness, reaching symmetric quadriparesis with proximal muscle strength of 2/5 in upper limbs and 1/5 in lower limbs. Following sintilimab discontinuation, treatment with intravenous immunoglobulin (2 g/kg) and oral prednisone (30 mg/day) achieved complete neurological recovery within one month. Given the patient's favorable initial tumor response and strong request, immunotherapy was cautiously reinstated using tislelizumab after thorough clinical evaluation. Following four cycles of treatment, significant tumor response enabled successful conversion surgery with major pathological response (necrosis rate >70%). With 26-month survival and no evidence of recurrence, this case demonstrates the potential feasibility of ICI rechallenge with an alternative PD-1 inhibitor following sintilimab-induced GBS. Our experience suggests that ICI-related neurological adverse events may be drug-specific rather than class-specific, potentially providing valuable treatment options for patients showing favorable tumor response despite experiencing severe IRAEs, though larger studies are needed for validation.

Immunotherapy-related neurotoxicity in the central nervous system of children with cancer

Significant gaps remain in our understanding of immunotherapy-related neurotoxicity in pediatric patients, largely because much of our knowledge comes from studies in adults. Accurately identifying the adverse effects of immunotherapy in children is also challenging, owing to variations in terminology and grading systems. Moreover, the manifestation of immunotherapy-related neurotoxicity differs greatly across different diseases, various modalities, dosages, and delivery methods. Combining immunotherapy with other treatments might improve outcomes but introduces new complexities and potential for increased toxicities. Additionally, pediatric patients with intracranial malignancy have unique responses to immunotherapies and distinct neurotoxicity compared to those with extracranial malignancy. Consequently, we must enhance our understanding of the pathophysiology, prevalence, severity, and management of immunotherapy's neurotoxic effects in this vulnerable group. This review consolidates the current knowledge of immunotherapy-related neurotoxicity in pediatric oncology, highlighting various types of neurotoxicity including cytokine release syndrome (CRS), immune effector cell-associated neurotoxicity syndrome (ICANS), and tumor inflammation-associated neurotoxicity (TIAN), among others. Furthermore, we examine the unique features of neurotoxicity associated with adoptive cellular therapy (ACT), antibody-based therapies, immune checkpoint inhibitors (ICIs), oncolytic viruses (OV), and cancer vaccines.

PD-1/PD-L1 checkpoint inhibitor-induced encephalitis in patients with lung adenocarcinoma: a report of three cases

Immune checkpoint inhibitor (ICI)-induced encephalitis is rare. We present three cases of encephalitis associated with ICIs in lung adenocarcinoma patients. These patients presented with a variety of symptoms, but one of the common symptoms for all patients was loss of consciousness. All patients responded well to steroid treatment and survived longer than one month after the onset of symptoms. These cases highlight the difficulties in diagnosing encephalitis based only on clinical information, and timely management is important to improve survival. Opportunistic infections also have to be ruled out to diagnose ICI-induced encephalitis especially when brain metastases co-exist.

Pembrolizumab-induced myasthenia gravis with isolated diaphragmatic involvement in a lung cancer patient: a case report

Immune-related neuromuscular disorders are rare and potentially life-threatening adverse events of immune checkpoint inhibitors (ICIs) used in the treatment of cancer. They tend to have a chronic course that usually leads to the permanent discontinuation of immunotherapy. We present a case of pembrolizumab-induced myasthenia gravis that only involved the diaphragm. The patient is a 71-year-old female with a history of stage IV lung adenocarcinoma under maintenance therapy with pemetrexed and pembrolizumab after a complete response to first-line chemo-immunotherapy. She complained of orthopnea since the previous month and was admitted due to hypoxemic respiratory failure. Radiology showed decreased lung volumes and atelectatic areas in both lower lung fields. A subsequent bronchoscopy ruled out infection and cancer recurrence. Pulmonary function tests revealed a mixed disorder with a severe reduction in maximal inspiratory pressure and a large drop in vital capacity in the supine versus the sited position. Ultrasonography of the diaphragm confirmed bilateral diaphragmatic dysfunction, and the patient was initiated on non-invasive ventilation (NIV) during sleep, which led to symptom relief. A neurological physical examination did not reveal any other muscle involvement. Laboratory tests for myasthenic syndromes showed an elevated titer of the anti-acetylcholine receptor antibody, which confirmed the diagnosis of myasthenia gravis. The patient was subsequently treated with corticosteroids, pyridostigmine, and intravenous immunoglobulin and was gradually able to wean off supplemental oxygen. On follow-up, her chest X-ray and spirometry had improved, but she continued sleeping on NIV. Pembrolizumab was stopped, and she is still free of cancer after 9 months. Clinicians treating cancer patients with immunotherapy should be aware of this rare complication and perform timely investigations in any case of orthopnea in the course of ICI therapy to offer specialized management.

Central nervous system complications of immune checkpoint inhibitors: A comprehensive review

The ever-increasing use of immune checkpoint inhibitors (ICIs) has significantly improved cancer management, but at the cost of frequent immunologic side effects. Among them, neurologic immune-related adverse events (nirAEs) are less common but pose a challenge to clinicians due to their severity, heterogeneous nature and nonspecific clinical presentation, making diagnosis complex. The prognosis of these nirAEs, especially those related to the central nervous system (CNS), correlates with their rapid recognition and therapeutic management. Indeed, the therapeutic options are sometimes unfamiliar and may be further complicated by the lack of recommendations in the event of failure of a well-managed first-line treatment. Finally, the attribution of ICIs to certain CNS disorders is controversial and may lead to an incorrect decision to discontinue or contraindicate treatment, resulting in an irremediable loss of opportunity for the patient. Therefore, the aim of this review is to present known/suspected CNS nirAEs induced by ICI, their diagnostic approach and management through therapeutic advices for optimal treatment and rechallenge opportunities.

AIEgen-self-assembled nanoparticles with anti-PD-L1 antibody functionalization realize enhanced synergistic photodynamic therapy and immunotherapy against malignant melanoma

Immune checkpoint inhibitors (ICIs) become integral in clinical practice, yet their application in cancer therapy is constrained by low overall response rates and the primary resistance of cancers to ICIs. Herein, this study proposes aggregation-induced emission (AIE)-based nanoparticles (NPs) for a more effective and synergistic approach combining immunotherapy and photodynamic therapy (PDT) to achieve higher responses than anti-PD-L1 monotherapy. The TBP@aPD-L1 NPs are constructed by functionalizing azide group-modified TBP-2 (TBP-N3) with anti-PD-L1 antibodies via the DBCO-S-S-PEG2000-COOH linker. The anti-PD-L1 target the tumor cells and promote the TBP-N3 accumulation in tumors for enhanced PDT. Notably, the TBP-N3, featuring aggregation-induced emission, boosts reactive oxygen species (ROS) generation through both type I and type II processes for enhanced PDT. The TBP@aPD-L1-mediated PDT induces more powerful effects of direct tumor cell-killing and further elicits effective immunogenic cell death (ICD), which exerts anti-tumor immunity by activating T cells for ICI treatment and reshapes the tumor immune microenvironment (TIME), thereby enhancing the efficacy of PD-L1 blockade of anti-PD-L1. Consequently, TBP@aPD-L1 NPs demonstrated significantly enhanced inhibition of tumor growth in the mouse model of malignant melanoma (MM). Our NPs act as a facile and effective drug delivery platform for enhanced immunotherapy combined with enhanced PDT in treating MM.

Immune-related encephalitis after immune checkpoint inhibitor therapy

BACKGROUND

Immune checkpoint inhibitors (ICI) have revolutionized cancer treatment but can trigger immune-related encephalitis. We report one of the largest case series of patients with immune-related encephalitis and review of the literature.

METHODS

Retrospective series of patients with immune-related encephalitis and literature review.

RESULTS

Fourteen patients with cancer treated with ICI (50% combination therapy) developed immune-related encephalitis. Diagnostic testing revealed cerebral spinal fluid (CSF) lymphocytic pleocytosis (85%) and elevated protein (69%), abnormal brain magnetic resonance imaging(MRI) (33%) or brain FDG-PET (25%), electroencephalogram (EEG) abnormalities (30%), and autoantibodies (31%). Encephalitis treatment included: corticosteroids (86%), intravenous immunoglobulin (IVIg) (36%), plasmapheresis (7%), and rituximab (29%). There were no deaths and 12 patients had significant recovery, although long-term complications were observed. All patients discontinued ICI. Longitudinal follow-up demonstrated anti-cancer response to ICI at 3 months (85%) and 6 months post-ICI initiation (77%). A literature review identified 132 patients with immune-related encephalitis. Most were treated with PD-1 inhibitors (18% combination). Common abnormalities included elevated CSF protein (84%) or pleocytosis (77%), abnormal brain MRI (65%), or autoantibodies (47%). Nearly all were treated with corticosteroids, many required additional therapy with IVIg (26%) or rituximab (12%). Most patients had clinical improvement (81%) but a minority (10%) had a clinical relapse after completing corticosteroid taper. ICIs were resumed in 7 patients (5%), with relapse in 3.

CONCLUSIONS AND RELEVANCE

Immune-related encephalitis is treatable and improves with corticosteroids in most cases but may require additional immunosuppression. Re-emergence of encephalitis is rare and does not typically result in adverse outcomes, and this should be considered in neurological immune-related adverse event management guidelines.

Differential diagnosis in immune checkpoint inhibitors neurotoxicity

BACKGROUND

Neurologic symptoms seen in patients receiving immune checkpoint inhibitors (ICI) may not be entirely caused by immunotoxicity. We aim to highlight these confounding conditions through clinical cases to encourage early recognition and management.

METHODS

We describe a series of seven cases from our institution that were treated with ICI and presented with Neurologic symptoms and were diagnosed with superimposed conditions beyond immunotoxicity.

RESULTS

A total of 7 cases are described that include acute motor axonal neuropathy with vitamin B12 deficiency, lumbosacral radiculopathy with Wernicke's, Herpes simplex virus (HSV) encephalitis reactivation, central nervous system vasculitis with renal vasculitis, myositis with fasciitis, myositis with fixed clinical deficit at resolution, and synovitis with accompanying carpal tunnel syndrome. Primary cancer site included lung adenocarcinoma (2/7), melanoma (4/7), and oropharyngeal squamous cell carcinoma (1/7). All patients had received treatment with more than one ICI. Median number of cycles prior to neurotoxicity was 3 cycles.

DISCUSSION

Neurologic symptoms seen in patients receiving ICI may include other causes beyond immunotoxicity.

Neuro-toxicities of chemo- and immune-therapies in haematologic malignancies: from mechanism to management

Chemo- and immune therapies administered to treat haematologic malignancies frequently cause neurologic injury. The adverse events range from mild cognitive impairment and headaches to severe conditions such as seizures, stroke and encephalitis. We performed a comprehensive literature review and report the types, mechanisms, management and prevention of neuro-toxicity resulting from these therapies in subjects who develop these toxic effects. Our paper will not discuss radiation therapy, as it has already been extensively reviewed by many authors. Our focus will be on recently developed anti-cancer drugs.

Immune Checkpoint Inhibitor Myopathy: The Double-Edged Sword of Cancer Immunotherapy

Immune checkpoint inhibitor (ICI) therapy has revolutionized the treatment of several malignancies, with improved survival. These monoclonal antibodies target immune checkpoints, including cytotoxic T-lymphocyte-associated protein 4 (ipilimumab and tremelimumab), programmed death 1 (nivolumab, pembrolizumab, cemiplimab, and dostarlimab), programmed death ligand 1 (atezolizumab, avelumab, and durvalumab), and lymphocyte activation gene 3 (relatlimab), and effectively augment the immune response against tumor cells. Releasing the brakes on the immune system has consequences, however, in the form of immune-related adverse events (irAEs), which may affect any organ. Neurologic irAEs represent 1%-3% of all irAEs, with immune-mediated myopathy (ICI myopathy) being the most common manifestation. Recent large patient series and systematic reviews have established the key features and highlighted new insights into ICI myopathy. ICI myopathy is characterized by an acute or subacute onset of oculobulbar and/or proximal limb weakness, with or without associated respiratory insufficiency and myocarditis. Creatine kinase elevation is common. Oculobulbar presentations with or without respiratory failure may be misattributed to neuromuscular junction disorders, particularly because acetylcholine receptor antibodies are present in up to 40% of patients; however, an electrodiagnostic evidence of a defect of neuromuscular transmission is often absent even in patients with severe weakness, highlighting that the myopathic process is the driving force behind these presentations. Muscle histopathology commonly demonstrates a unique signature of multifocal clusters of necrotic and regenerating fibers, differentiating ICI myopathy from other autoimmune myopathies. Transcriptomic analysis has uncovered distinct subgroups within ICI myopathy, revealing varying degrees of type 1 and type 2 interferon pathway activation alongside notable upregulation of the interleukin (IL)-6 pathway in affected muscle tissue. This discovery presents a promising avenue for intervention through the use of therapies that suppress the interferon pathway and target IL-6 or its receptor. Despite clinical improvements with immunomodulatory therapy, with corticosteroids the mainstay of treatment, mortality remains high, particularly in those with associated myocarditis or respiratory failure requiring intubation, where mortality occurs in up to 50%. ICI withdrawal can lead to cancer progression and death, highlighting a need for improved approaches to ICI rechallenge, performed in limited patients with variable success to date.

Immune Checkpoint Inhibitor-Related Cerebellar Toxicity: Clinical Features and Comparison with Paraneoplastic Cerebellar Ataxia

Immune checkpoint inhibitors (ICIs) have revolutionized cancer therapy, and the association with immune-related adverse events (irAEs) is well-established. However, cerebellar irAEs are poorly defined and their relationship with paraneoplastic disorders remains unclear. Our aim was (i) to characterize cerebellar irAE; (ii) to compare it with paraneoplastic cerebellar ataxia (PCA). We performed a multicenter, retrospective, cohort study of patients developing new-onset, immune-mediated, isolated/predominant cerebellar dysfunction after ICI administration. In addition, a systematic review following PRISMA guidelines was performed. Cerebellar irAE cases were compared with a consecutive cohort of patients with PCA. Overall, 35 patients were included, of whom 12 were original cases (males: 25/35 (71%), median age: 65 [range: 20-82]). The most frequent tumor was non-small cell lung cancer (12/35, 34%). Anti-PD1 were adopted in 19/35 (54%). Symptoms developed at a median of 11 weeks after ICI onset. Neuronal antibodies were detected in 15/31 patients tested (48%). Cerebrospinal fluid was inflammatory in 25/30 (83%). Magnetic resonance imaging showed cerebellar hyperintensities in 8/35 (23%). Immunotherapy was applied in 33/35 cases (94%), and most patients improved with residual disability (16/35, 46%). When compared with a series of PCA (n = 15), the cerebellar irAE group was significantly more associated with male sex, lung cancer (rather than gynecological/breast cancers), isolated ataxia, and a better outcome. We provide a detailed characterization of cerebellar irAE. Compared to PCA, differences exist in terms of tumor association, clinical features, and outcome. Clinical presentation-antibody-tumor triad in the ICI group only partially reflects the associations described in paraneoplastic disorders.

Immune checkpoint inhibition of metastatic melanoma: achieving high efficacy in the face of high toxicity

INTRODUCTION

Immune checkpoint inhibitors (ICIs) have advanced the treatment of metastatic melanoma by blocking immune system down-regulators enhancing T-cell-mediated anti-tumor responses. However, many ICIs induce immune-related adverse effects (irAEs) that can impact many organ systems.

AREAS COVERED

Strategies used to manage irAEs include corticosteroids, anti-tumor necrosis factor alpha (TNF-α) agents, other biological therapies, fecal microbiota transplantation (FMT), and emerging regimens. In this review, we describe current evidence for the efficacy of ICIs, acute and chronic immune toxicities, and strategies to manage toxicities for patients treated with ICIs.

EXPERT OPINION

IrAE management will likely evolve by developing more tailored approaches to prevent toxicities, improving non-steroidal management strategies and tailoring the dose of steroids, and identifying biomarkers of severe toxicities.

Paraneoplastic Neurologic Syndromes Associated With Merkel Cell Carcinoma

BACKGROUND AND OBJECTIVES

To define the clinical and immunologic profile of patients with paraneoplastic neurologic syndromes (PNSs) associated with Merkel cell carcinoma (MCC).

METHODS

Retrospective analysis was conducted on patients with suspected MCC-related PNS assessed at the French Reference Center, and cases were identified by a systematic review of the literature (MEDLINE, Embase) following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines.

RESULTS

A total of 17 patients were identified in our center and 30 in the systematic review, resulting in an overall cohort of 47 patients. The median age was 65 years (range 41-90), and 30 of 46 (65%) were men. Lambert-Eaton myasthenic syndrome (LEMS) (14/47, 29%), rapidly progressive cerebellar syndrome (11/47, 23%), and encephalomyelitis (EM) (8/47, 17%) were the most common associated clinical phenotypes. The most frequently associated neural antibodies (Abs) were voltage-gated calcium channel (VGCC)-Abs (14/45, 31%), followed by Hu-Abs (8/45, 17%) and neurofilament (NF)-Abs (8/45, 17%). Patients with NF-Abs only exhibited CNS disorders (8/8, 100%) and often had antibodies against >1 NF subunit (6/8, 75%). At onset, 26 of 43 patients (60%) had no identifiable primary skin tumor but had lymph node metastasis; these patients were more frequently men (21/26, 80%, vs 7/17, 41%; p = 0.007), had more frequently VGCC-Abs (12/26, 46%, vs 2/17, 11%, p = 0.02) predominantly among those with LEMS, and presented reduced mortality than patients with a known primary tumor (5/25, 20%, vs 8/15, 53%; p = 0.02).

DISCUSSION

MCC-related PNSs present as a heterogeneous clinical spectrum including central and/or peripheral nervous system disorders such as LEMS, RCPS, and EM, mainly associated with VGCC-Abs, NF-Abs, and Hu-Abs. NF-Abs were only seen among patients with CNS disorders. At onset, the absence of a primary skin tumor but presence of lymph node metastasis is frequently observed, and this particular clinical presentation is linked to reduced mortality, highlighting distinctive clinical and immunologic features of MCC-related PNS.

Case report: Immune checkpoint inhibitor-induced paraneoplastic neurological syndrome in two patients: a case series

Immune checkpoint inhibitors (ICIs) combined with chemotherapy have improved overall survival in patients with small-cell lung cancer, but have also led to an increase in adverse effects. The incidence of ICI-induced paraneoplastic neurological syndrome (PNS) is relatively low when the primary lung lesion is well controlled. However, it is associated with high mortality and disability rates. In this report, we present two cases of extensive-stage small-cell lung cancer with neurological symptoms and positive paraneoplastic antibodies in the serum and cerebrospinal fluid (CSF) following ICI therapy. Although the symptoms improved after treatment with systemic high-dose immunoglobulin and glucocorticoids, one patient, unfortunately, succumbed to tumor progression four months later, whereas the other patient experienced persistent difficulty in standing and walking despite improved muscle strength. In cases where neurological symptoms that cannot be explained by tumor metastases arise during ICI treatment, paraneoplastic syndromes should be considered and testing for antineuronal antibodies is crucial, as early detection and intervention can help mitigate their impact. Further research is needed to develop better predictive strategies and treatment protocols for these adverse reactions.

Extra-Limbic Seronegative Encephalitis Preceding Recurrent Hodgkin's Lymphoma and Gastric Diffuse Large B-Cell Lymphoma: A Case Report

We describe a patient with extra-limbic seronegative encephalitis with relapsing progressive course as the harbinger of sequential Hodgkin's lymphoma and Diffuse Large B-Cell lymphoma. Diagnosis of probable paraneoplastic neurologic syndrome (PNS) was arrived at by exhaustive elimination of alternative causes and supportive tissue diagnosis. This case highlights the phenotypic variety of paraneoplastic neurologic syndromes associated with hematologic malignancies and the challenges in their recognition, diagnosis, and treatment. We discuss and apply the updated consensus diagnostic criteria for paraneoplastic syndromes to our case as a means of bolstering probability in cases of diagnostic uncertainty.

Peripheral nervous system immune-related adverse events due to checkpoint inhibition

Immune checkpoint inhibitors have revolutionized cancer therapy and are increasingly used to treat a wide range of oncological conditions, with dramatic benefits for many patients. Unfortunately, the resulting increase in T cell effector function often results in immune-related adverse events (irAEs), which can involve any organ system, including the central nervous system (CNS) and peripheral nervous system (PNS). Neurological irAEs involve the PNS in two-thirds of affected patients. Muscle involvement (immune-related myopathy) is the most common PNS irAE and can be associated with neuromuscular junction involvement. Immune-related peripheral neuropathy most commonly takes the form of polyradiculoneuropathy or cranial neuropathies. Immune-related myopathy (with or without neuromuscular junction involvement) often occurs along with immune-related myocarditis, and this overlap syndrome is associated with substantially increased mortality. This Review focuses on PNS adverse events associated with immune checkpoint inhibition. Underlying pathophysiological mechanisms are discussed, including antigen homology between self and tumour, epitope spreading and activation of pre-existing autoreactive T cells. An overview of current approaches to clinical management is provided, including cytokine-directed therapies that aim to decouple anticancer immunity from autoimmunity and emerging treatments for patients with severe (life-threatening) presentations.

Pembrolizumab-Induced Myasthenia Gravis With Myocarditis in the Setting of Metastatic Renal Cell Carcinoma

Immune checkpoint inhibitors (ICIs) like pembrolizumab are increasingly used for treating renal cell carcinoma (RCC), offering benefits such as enhanced specificity and activation of immunological memory. However, ICIs can lead to immune-related adverse events (irAEs), including rare but serious neurologic consequences such as myasthenia gravis (MG). We present a case of pembrolizumab-induced MG with concurrent orbital myositis and myocarditis. A 69-year-old male with a history of pT3aN1 kidney cancer presented with abdominal pain, night sweats, and weight loss. Initial imaging revealed a retroperitoneal mass and a thyroid mass, and a biopsy confirmed papillary RCC. The patient began neoadjuvant therapy with pembrolizumab and axitinib. Three weeks post-initiation, he developed dysphagia, ptosis, and proptosis, which progressed with each pembrolizumab infusion. Hospitalization was required after the third cycle due to bilateral ptosis, heart block, and elevated troponins. Despite initial steroid treatment, symptoms persisted. Diagnoses of ICI-related MG (irMG) and myocarditis were established, and treatment included cessation of pembrolizumab, high-dose steroids, IVIGs, and a pacemaker for heart block. Post-discharge, the patient showed a slight improvement in ptosis but persistent dysphagia. MG induced by ICIs is a rare but severe complication with rapid onset and progression, often presenting with bulbar involvement and a significant risk of respiratory failure. The therapeutic regimen for our patient, including high-dose methylprednisolone and IVIG, aligns with current recommendations. This case underscores the importance of recognizing cardiac irAEs like myocarditis in patients on ICIs, as early intervention can significantly affect outcomes. Despite therapeutic interventions, complete resolution of irMG symptoms is rare, and persistent sequelae are common. This case highlights the critical need for vigilant monitoring and prompt management of neurologic and cardiac irAEs in patients undergoing ICI therapy. Clinicians should maintain a high index of suspicion for MG and myocarditis to improve diagnostic accuracy and patient outcomes.

Autoimmune Neuromuscular Disorders Associated With Neural Antibodies

OBJECTIVE

This article reviews autoimmune neuromuscular disorders and includes an overview of the diagnostic approach, especially the role of antibody testing in a variety of neuropathies and some other neuromuscular disorders.

LATEST DEVELOPMENTS

In the past few decades, multiple antibody biomarkers associated with immune-mediated neuromuscular disorders have been reported. These biomarkers are not only useful for better understanding of disease pathogenesis and allowing more timely diagnosis but may also aid in the selection of an optimal treatment strategy.

ESSENTIAL POINTS

Recognition of autoimmune neuromuscular conditions encountered in inpatient or outpatient neurologic practice is very important because many of these disorders are reversible with prompt diagnosis and early treatment. Antibodies are often helpful in making this diagnosis. However, the clinical phenotype and electrodiagnostic testing should be taken into account when ordering antibody tests or panels and interpreting the subsequent results. Similar to other laboratory investigations, understanding the potential utility and limitations of antibody testing in each clinical setting is critical for practicing neurologists.

Paraneoplastic Neurologic Disorders

OBJECTIVE

This article reviews the clinical presentations, neural antibody associations, and oncologic accompaniments of paraneoplastic neurologic syndromes and neurologic autoimmunity in the context of immune checkpoint inhibitor (ICI) cancer immunotherapy.

LATEST DEVELOPMENTS

Neural antibody discovery has improved the diagnosis of paraneoplastic neurologic syndromes. Neural antibodies also delineate the underlying disease pathophysiology and thus inform outcomes and treatments. Neural antibodies specific for extracellular proteins have pathogenic potential, whereas antibodies specific for intracellular targets are biomarkers of a cytotoxic T-cell immune response. A recent update in paraneoplastic neurologic syndrome criteria suggests high- and intermediate-risk phenotypes as well as neural antibodies to improve diagnostic accuracy in patients with paraneoplastic neurologic syndromes; a score was created based on this categorization. The introduction of ICI cancer immunotherapy has led to an increase in cancer-related neurologic autoimmunity with distinct clinical phenotypes.

ESSENTIAL POINTS

Paraneoplastic neurologic syndromes reflect an ongoing immunologic response to cancer mediated by effector T cells or antibodies. Paraneoplastic neurologic syndromes can present with manifestations at any level of the neuraxis, and neural antibodies aid diagnosis, focus cancer screening, and inform prognosis and therapy. In patients with high clinical suspicion of a paraneoplastic neurologic syndrome, cancer screening and treatment should be undertaken, regardless of the presence of a neural antibody. ICI therapy has led to immune-mediated neurologic complications. Recognition and treatment lead to improved outcomes.

Orofacial complications from immune checkpoint inhibitors: A retrospective analysis from two academic medical centers

BACKGROUND

Immune checkpoint inhibitors (ICIs) are FDA-approved for various cancers, yet their orofacial immune-related adverse events (irAEs) remain poorly understood. Our two-center retrospective study aims to better understand the prevalence and nature of these orofacial irAEs.

METHODS

We retrospectively collected demographics, ICI details, and onset of orofacial irAEs in ICI-treated patients at University of California San Francisco and City of Hope (2013-2021). Orofacial irAEs were identified by ICD-10 codes and data categorized as dry mouth/xerostomia, oral mucosal lesions, and orofacial neuropathies. Patients with pre-existing orofacial conditions resembling the reported irAEs were excluded.

RESULTS

Among 3768 ICI-treated patients, 408 (10.8%) developed 467 orofacial irAEs: oral mucosal diseases (41.4%), dry mouth/xerostomia (41.0%), and orofacial neuropathies (17.6%). Notably, head and neck cancers had the highest incidence of orofacial irAEs.

CONCLUSIONS

Orofacial irAEs are relatively common in patients receiving ICIs, necessitating careful monitoring and management of these complications during and after the treatment.

Unravelling the Acute, Chronic and Steroid-Refractory Management of High-Grade Neurological Immune-Related Adverse Events: A Call to Action

Rare side effects of immune-checkpoint inhibitors (ICIs) are known as neurological immune-related adverse events (n-irAEs). Typically, n-irAEs affect the peripheral nervous system, primarily presenting as myositis, polyradiculoneuropathy, or cranial neuropathy. Less commonly, they impact the central nervous system, resulting in encephalitis, meningitis, or myelitis. High-grade n-irAEs managing and recognizing remains challenging, considering the risk of mortality and long-term disability. To date, strong scientific data are lacking to support the management of high-grade clinical forms. We performed a systematic literature search, selecting all articles describing high-grade steroid-resistance n-irAEs. and we reported them in a practical review. Specifically, current recommendations advise stopping ICI use and beginning corticosteroid treatment. Our findings highlighted that in steroid-resistant n-irAEs, it should be recommended to quickly escalate to plasma exchange (PLEX) and/or intravenously immunoglobulins (IVIg), usually in association with other immunosuppressants. Furthermore, newer evidence supports the use of drugs that may specifically block inflammation without reducing the anti-tumour effect of ICIs. In this practical review, we provide new evidence regarding the therapeutic approach of high-grade n-irAEs, particularly in steroid-resistant cases. We would also stress the importance of informing the scientific community of the discrepancy between current guidelines and clinical evidence in these rare forms of pathology.

Pituitary Complications of Checkpoint Inhibitor Use

Immune checkpoint inhibitors have revolutionized cancer therapy but are associated with a risk of endocrine immune-related adverse events, including pituitary complications. Autoimmune hypophysitis, traditionally a rare diagnosis, has become a more frequently encountered clinical entity with the emergence of antitumor immunotherapy. This mini-review aims to consolidate current knowledge, encompassing the epidemiology, pathophysiology, clinical presentation, diagnosis, and management of pituitary complications of immune checkpoint inhibitor use.

Chronic immune-related adverse events arising from immune checkpoint inhibitors: an update

Immune checkpoint inhibitors (ICIs) have transformed cancer treatment, improving outcomes for many patients. However, toxicities termed immune-related adverse events (irAEs) are limitations of these revolutionary treatments. These irAEs may resolve with treatment or ICI cessation (acute) or persist many months beyond therapy cessation (chronic). Acute irAEs were the first to be recognized and are thus more well studied. However, chronic irAEs have been highlighted in recent years and are becoming a topic of more intensive investigation. These chronic irAEs have been noted to affect many different organ systems, including endocrine, rheumatologic, gastrointestinal, dermatologic, neurologic, and cardiovascular systems. In this review, we discuss current knowledge surrounding the frequency, time course, and risk factors associated with chronic irAEs affecting various organ systems, treatment approaches, and future directions.

Cerebral 18F-FDG PET/CT Metabolism as Diagnostic Signature for Central Nervous System Toxicity After Immune Checkpoint Blockade Cancer Treatment

Our aim was to investigate probable biomarkers specific to immune-related central nervous system toxicity (CNST) in cancer patients treated with immune checkpoint inhibitors (ICI) by analysis of 18F-FDG PET/CT images. Methods: Cancer patients receiving ICI treatment were enrolled in a multicenter observational study that analyzed regional metabolic changes before and during CNST onset from January 2020 to February 2022. In 1:1 propensity score-matched pairs, the regional SUVmean of each bilateral brain lobe of CNST patients (CNST+) was compared with that of patients who had central nervous system infections (CNSIs) and patients without CNST or CNSI (CNST-). In a validation cohort, patients were recruited from February 2022 to July 2023 and followed up for 24 wk after the start of ICI. Early changes in regional SUVmean at 5-6 wk after therapy initiation were evaluated for ability to predict later CNST onset. Results: Of 6,395 ICI-treated patients, 2,387 underwent prognostic 18F-FDG PET/CT and 125 of the scanned patients had CNST (median time from ICI treatment to onset, 9 wk; quartile range, 2-23 wk). Regional 18F-FDG PET/CT SUVmean changes were higher in CNST+ than in CNST- patients (117 patient pairs) but were lower than in CNSI patients (50 pairs). Differentiating analysis reached an area under the curve (AUC) of 0.83 (95% CI, 0.78-0.88) for CNST+ versus CNST- and of 0.80 (95% CI, 0.72-0.89) for CNST+ versus CNSI. Changes in SUVmean were also higher before CNST onset than for CNST- (60 pairs; AUC, 0.74; 95% CI, 0.66-0.83). In a validation cohort of 2,878 patients, preonset changes in SUVmean reached an AUC of 0.86 (95% CI, 0.79-0.94) in predicting later CNST incidence. Conclusion: Brain regional hypermetabolism could be detected during and before CNST clinical onset. CNST may be a distinct pathologic entity versus brain infections defined by 18F-FDG PET/CT brain scans. Regional SUV differences may be translated into early diagnostic tools based on moderate differentiating accuracy in our study.

Neurological Immune-Related Adverse Events Induced by Immune Checkpoint Inhibitors

The use of immune checkpoint inhibitors (ICIs) for the treatment of various advanced and aggressive types of malignancy has significantly increased both survival and long-term remission rates. ICIs block crucial inhibitory pathways of the immune system, in order to trigger an aggravated immune response against the tumor. However, this enhanced immune activation leads to the development of numerous immune-related adverse events (irAEs), which may affect any system. Although severe neurological irAEs are relatively rare, they carry a high disability burden, and they can be potentially life-threatening. Therefore, clinicians must be alert and act promptly when individuals receiving ICIs present with new-onset neurological symptoms. In this narrative review, we have collected all the currently available data regarding the epidemiology, pathogenesis, clinical manifestations, diagnosis, and treatment of post-ICI neurological irAEs. This review aims to raise physicians' awareness, enrich their knowledge regarding disease pathogenesis, and guide them through the diagnosis and management of post-ICI neurological irAEs.

Central nervous system adverse events of immune checkpoint inhibitors

PURPOSE OF REVIEW

Immune checkpoint inhibitors (ICI) may trigger immune-related adverse events which rarely affect the central nervous system (CNS-irAEs). Over the past few years, cumulative data have led to the characterization of well defined syndromes with distinct cancer and antibody associations as well as different outcomes.

RECENT FINDINGS

The most frequent CNS-irAE is encephalitis, which includes three main groups: meningoencephalitis, a nonfocal syndrome usually responsive to corticosteroids; limbic encephalitis, associated with high-risk paraneoplastic neurological syndromes (PNS) antibodies (e.g. anti-Hu, anti-Ma2) and neuroendocrine cancers, characterized by poor treatment response and outcomes; and cerebellar ataxia, with variable outcomes (worse when high-risk PNS antibodies are detected). Additionally, a diffuse encephalopathy without inflammatory findings, with poor response to corticosteroids and high mortality has been described. The spectrum of CNS-irAEs also includes meningitis, myelitis, and rarer presentations. A subset of CNS-irAEs (i.e. limbic encephalitis and/or rapidly progressive cerebellar ataxia) is undistinguishable from ICI-naïve PNS.

SUMMARY

The clinical and outcomes diversity of CNS-irAEs suggests different pathogenic mechanisms, which need to be understood to establish more effective and specific treatment modalities. It is crucial to identify biomarkers able to predict which patients will experience severe CNS-irAEs, to anticipate their diagnosis, and to predict long-term outcomes.

Neurological autoimmunity in patients with non-pulmonary neuroendocrine neoplasms: clinical manifestations and neural autoantibody profiles

BACKGROUND AND PURPOSE

Paraneoplastic neurological autoimmunity is well described with small-cell lung cancer, but information is limited for other neuroendocrine neoplasms (NENs).

METHODS

Adult patients with histopathologically confirmed non-pulmonary NENs, neurological autoimmunity within 5 years of NEN diagnosis, and neural antibody testing performed at the Mayo Clinic Neuroimmunology Laboratory (January 2008 to March 2023) were retrospectively identified. Control sera were available from patients with NENs without neurological autoimmunity (116).

RESULTS

Thirty-four patients were identified (median age 68 years, range 31-87). The most common primary tumor sites were pancreas (nine), skin (Merkel cell, eight), small bowel/duodenum (seven), and unknown (seven). Five patients received immune checkpoint inhibitor (ICI) therapy before symptom onset; symptoms preceded cancer diagnosis in 62.1% of non-ICI-treated patients. The most frequent neurological phenotypes (non-ICI-treated) were movement disorders (12; cerebellar ataxia in 10), dysautonomia (six), peripheral neuropathy (eight), encephalitis (four), and neuromuscular junction disorders (four). Neural antibodies were detected in 55.9% of patients studied (most common specificities: P/Q-type voltage-gated calcium channel [seven], muscle-type acetylcholine receptor [three], anti-neuronal nuclear antibody type 1 [three], and neuronal intermediate filaments [two]), but in only 6.9% of controls. Amongst patients receiving cancer or immunosuppressive therapy, 51.6% had partial or complete recovery. Outcomes were unfavorable in 48.3% (non-ICI-treated) and neural autoantibody positivity was associated with poor neurological outcome.

DISCUSSION

Neurological autoimmunity associated with non-pulmonary NENs is often multifocal and can be treatment responsive, underscoring the importance of rapid recognition and early treatment.

Neurological autoimmunity in melanoma patients: a comparison between those exposed and non-exposed to immune checkpoint inhibitors

BACKGROUND

The clinical spectrum of melanoma-associated neurological autoimmunity, whether melanoma-associated paraneoplastic neurological syndromes (PNS) or induced by immune checkpoint inhibitors (ICI), is not well characterized. We aim to describe the clinical spectrum of melanoma-associated neurological autoimmunity.

METHODS

A systematic review of the literature combined with patients from French databases of paraneoplastic neurological syndromes was conducted. All melanoma patients with a possible immune-mediated neurologic syndrome were included and classified according to whether they had previously been exposed to ICI (ICI-neurotoxicity) or not (ICI-naïve) at first neurological symptoms.

RESULTS

Seventy ICI-naïve (literature: n = 61) and 241 ICI-neurotoxicity patients (literature: n = 180) were identified. Neuromuscular manifestations predominated in both groups, but peripheral neuropathies were more frequent in ICI-neurotoxicity patients (39.4% vs 21.4%, p = 0.005) whereas myositis was more frequent in ICI-naïve patients (42.9% vs 18.7%, p < 0.001). ICI-naïve patients had also more frequent central nervous system (CNS) involvement (35.7% vs 23.7%, p = 0.045), classical paraneoplastic syndrome (25.7% vs 5.8%, p < 0.001), and more frequently positive for anti-neuron antibodies (24/32, 75.0% vs 38/90, 42.2%, p = 0.001). Although more ICI-neurotoxicity patients died during the acute phase (22/202, 10.9% vs 1/51, 2.0%, p = 0.047), mostly myositis patients (14/22, 63.6%), mortality during follow-up was higher in ICI-naïve patients (58.5% vs 29.8%, p < 0.001). There was no significant difference in the frequency of life independence (mRS ≤ 2) in the surviving patients in both groups (95.5% vs 91.0%, p = 0.437).

CONCLUSIONS

Melanoma-associated PNS appear remarkably rare. The clinical similarities observed in neurological autoimmunity between ICI-treated and ICI-naïve patients, characterized predominantly by demyelinating polyradiculoneuropathy and myositis, suggest a potential prior immunization against melanoma antigens contributing to ICI-related neurotoxicity.

A bibliometric analysis of immune-related adverse events in cancer patients and a meta-analysis of immune-related adverse events in patients with hepatocellular carcinoma

Background and Objectives

Immunotherapy has become the standard treatment for hepatocellular carcinoma (HCC), but it carries a risk of immune-related adverse events (irAEs) that can be life-threatening. This study employs bibliometric analysis to understand global scientific research on irAEs in cancer, focusing on characteristics and areas of interest. Additionally, a meta-analysis provides a comprehensive overview of irAEs in HCC patients receiving immune checkpoint inhibitor (ICI)-based therapies.

Methods

We conducted a thorough search of Web of Science Core Collection (WoSCC) publications from 1999 to 2022. R and VOSviewer software were used for analysis. A meta-analysis was performed using data from PubMed, Embase, and the Cochrane Library databases up to March 22, 2022. Trials with HCC patients reporting irAE incidence were included. Quality assessment followed Cochrane risk of bias, Newcastle-Ottawa Scale (NOS), and Methodological Index for Non-Randomized Studies (MINORS). We used random-effects or fixed-effects models based on I2 values. Primary outcomes included any-grade irAEs and grade ≥ 3 irAEs. This review and meta-analysis are registered in PROSPERO as CRD42022318885.

Results

In bibliometric analysis, we included 2946 papers, showing a consistent rise in annual publications on irAEs in cancer research. Frequent keywords were "nivolumab", "immune checkpoint inhibitor", and "immune-related adverse event". "Hepatocellular carcinoma" emerged as a prominent research focus linked to irAEs. We conducted a comprehensive meta-analysis on irAE incidence in HCC patients, including 29 studies. The overall incidence of any-grade irAEs was 61.0% (95% CI 38.5%-81.3%), and grade ≥ 3 irAEs was 13.2% (95% CI 7.9%-19.6%). Treatment-related mortality occurred in 3.1% (95% CI 0.8%-6.3%), with treatment discontinuation at 10.7% (95% CI 6.3%-16.0%). Reactive cutaneous capillary endothelial proliferation (RCCEP) was the most common any-grade irAE, while elevated aspartate aminotransferase (AST) was the most common grade ≥ 3 irAE. Treatment strategies were independently associated with specific irAEs, as indicated by multivariable analysis.

Conclusion

This study provides valuable insights into the current research landscape of irAEs in cancer and ofers a comprehensive overview of irAEs in HCC patients undergoing ICI-based therapy. The relatively high incidence of irAEs and their association with treatment strategies emphasize the need for careful management by clinicians when treating HCC patients. These findings offer significant guidance for optimizing care and treatment for HCC patients.

Update on Neuro-ophthalmic Manifestations of Immune Checkpoint Inhibitors

PURPOSE OF REVIEW

Immune checkpoint inhibitor (ICI) use has been on the rise for treatment of many different malignancies. Subsequently, more has been learned about immune-related adverse events (irAEs) that occur up to 12 months after treatment. This review summarizes the latest findings and management of neuro-ophthalmic associated irAEs.

RECENT FINDINGS

irAEs can affect the afferent and efferent neuro-ophthalmic pathways, thereby targeting central and peripheral nervous systems. As more cases are being reported, it is becoming apparent that neuro-ophthalmic irAEs often present with atypical features when compared to their spontaneous autoimmune counterparts. These neuro-ophthalmic presentations can also be signs of a more extensive inflammatory process that spans other organ systems, such as myopathies, endocrinopathies, and paraneoplastic syndromes. Awareness of neuro-ophthalmic irAEs and their atypical presentations can lead to early detection, termination of ICI treatment, and immunosuppressant therapy initiation.

Autoimmune Movement Disorders Complicating Treatment with Immune Checkpoint Inhibitors

BACKGROUND

Immune checkpoint inhibitors (ICI) may trigger autoimmune neurological conditions, including movement disorders (MD).

OBJECTIVES

The aim of this study was to characterize MDs occurring as immune-related adverse events (irAEs) of ICIs.

METHODS

A systematic literature review of case reports/series of MDs as irAEs of ICIs was performed.

RESULTS

Of 5682 eligible papers, 26 articles with 28 patients were included. MDs occur as a rare complication of cancer immunotherapy with heterogeneous clinical presentations and in most cases in association with other irAEs. Inflammatory basal ganglia T2/fluid attenuated inversion recovery abnormalities are rarely observed, but brain imaging is frequently unrevealing. Cerebrospinal fluid findings are frequently suggestive of inflammation. Half of cases are associated with a wide range of autoantibodies. Steroids and ICI withdrawal usually lead to improvement, even though some patients experienced relapses or a severe clinical course.

CONCLUSION

MDs are a rare complication of ICIs that should be promptly recognized to offer patients a correct diagnosis and treatment.

Neurological Adverse Events Related to Immune Checkpoint Inhibitors: A Practical Review

The increasing use of immune checkpoint inhibitors (ICI) in cancer therapy has brought attention to their associated neurotoxicities, termed neurological immune-related adverse events (n-irAEs). Despite their relatively rare incidence, n-irAEs pose a significant risk, potentially leading to severe, long-lasting disabilities or even fatal outcomes. This narrative review aims to provide a comprehensive overview of n-irAEs, focusing on their recognition and management. The review addresses a spectrum of n-irAEs, encompassing myositis, myasthenia gravis, various neuropathies, and central nervous system complications, such as encephalitis, meningitis, and demyelinating diseases. The key features of n-irAEs are emphasized in this review, including their early onset after initiation of ICIs, potential association with non-neurological irAEs and/or concurrent oncological response, the significance of ruling out other etiologies, and the expected improvement upon discontinuation of ICIs and/or immunosuppression. Furthermore, this review delves into considerations for ICI re-challenge and the intricate nature of n-irAEs within the context of pre-existing autoimmune and paraneoplastic syndromes. It underscores the importance of a multidisciplinary approach to diagnosis and treatment, highlighting the pivotal role of severity grading in guiding treatment decisions.

Defining D-irAEs: consensus-based disease definitions for the diagnosis of dermatologic adverse events from immune checkpoint inhibitor therapy

With an increasing number of patients eligible for immune checkpoint inhibitors, the incidence of immune-related adverse events (irAEs) is on the rise. Dermatologic immune-related adverse events (D-irAEs) are the most common and earliest to manifest, often with important downstream consequences for the patient. Current guidelines lack clarity in terms of diagnostic criteria for D-irAEs. The goal of this project is to better define D-irAE for the purposes of identification, diagnosis, and future study of this important group of diseases.The objectives of this project were to develop consensus guidance for an approach to D-irAEs including disease definitions and severity grading. Knowing that consensus among oncologists, dermatologists, and irAE subspecialists would be critical for usability, we formed a Dermatologic irAE Disease Definition Panel. The panel was composed of 34 experts, including oncologists, dermatologists, a rheumatologist, and an allergist/immunologist from 22 institutions across the USA and internationally. A modified Delphi consensus process was used, with two rounds of anonymous ratings by panelists and two virtual meetings to discuss areas of controversy. Panelists rated content for usability, appropriateness, and accuracy on 9-point scales in electronic surveys and provided free text comments. A working group aggregated survey responses and incorporated them into revised definitions. Consensus was based on numeric ratings using the RAND/UCLA Appropriateness Method with prespecified definitions.Following revisions based on panelist feedback, all items received consensus in the second round of ratings. Consensus definitions were achieved for 10 core D-irAE diagnoses: ICI-vitiligo, ICI-lichen planus, ICI-psoriasis, ICI-exanthem, ICI-bullous pemphigoid, ICI-Grover's, ICI-eczematous, ICI-eruptive atypical squamous proliferation, ICI-pruritus without rash, and ICI-erosive mucocutaneous. A standard evaluation for D-irAE was also found to reach consensus, with disease-specific exceptions detailed when necessary. Each disorder's description includes further details on disease subtypes, symptoms, supportive exam findings, and three levels of diagnostic certainty (definite, probable, and possible).These consensus-driven disease definitions standardize D-irAE classification in a useable framework for multiple disciplines and will be the foundation for future work. Given consensus on their accuracy and usability from a representative panel group, we anticipate that they can be used broadly across clinical and research settings.

Immune-Related Peripheral Neuropathy Associated with Immune Checkpoint Inhibitors: Case Report and Review of Literature

Immune checkpoint inhibitors (ICIs) are a group of drugs that have improved outcomes for patients with various cancers. Generally considered safe and well tolerated, these drugs are occasionally linked to immune-mediated or immune-related adverse events. Among these, autoimmune neurological events are rare, displaying varying incidence rates across different studies. Peripheral neuropathy, although one of the more common neurological immune-related events, is at times underestimated. This case report highlights an adult patient diagnosed with metastatic intrahepatic cholangiocarcinoma. Initially, the patient underwent chemoimmunotherapy with gemcitabine, cisplatin, and durvalumab for eight cycles, achieving partial response without significant toxicity. Following this, the patient continued with maintenance monotherapy with durvalumab every 28 days. After completing six cycles of maintenance therapy, the patient suddenly experienced paresthesia and hypoesthesia in four limbs, accompanied by apraxia in the hands that was more pronounced on the right side. Additionally, the patient reported neuropathic pain in the right arm and encountered limitations in certain instrumental activities of daily living. Diagnostic studies, including laboratory and electrophysiological studies, combined with the clinical presentation, identified immune-related peripheral polyneuropathy. Durvalumab was suspended and prednisolone therapy was initiated, resulting in a rapid resolution of all neuropathic symptoms. In addition to the clinical case, this article reviews the literature on immunotherapy-associated peripheral neuropathy.

Neuromuscular problems of the critically Ill neonate and child

Acute neuromuscular disorders occasionally occur in the Pediatric Neurologic Intensive Care Unit. Many of these are primary disorders of the motor unit that may present acutely or exacerbate during an intercurrent illness. Additionally, acute neuromuscular disorders may develop during an acute systemic illness requiring intensive care management that predispose the child to another set of acute motor unit disorders. This chapter discusses acute neuromuscular crises in the infant, toddler, and adolescent, as well as neuromuscular disorders resulting from critical illness.

Dataset for: Autoantibody profiles in patients with immune checkpoint inhibitor-induced neurological immune-related adverse events

The rise of cancer immunotherapy has been a milestone in clinical oncology. Above all, immune checkpoint inhibitor treatment (ICI) with monoclonal antibodies targeting programmed cell death protein 1 (PD-1), programmed cell death-ligand 1 (PD-L1), and cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) has improved survival rates for an increasing number of malignancies. However, despite the clinical benefits, ICI-related autoimmunity has become a significant cause of non-relapse-related morbidity and mortality. Neurological immune-related adverse events (irAE-n) are particularly severe toxicities with a high risk for chronic illness, long-term steroid dependency, and early ICI treatment termination. While the clinical characteristics of irAE-n are well described, little is known about underlying immune mechanisms and potential biomarkers. Recently, high frequencies of neuronal autoantibodies in patients with irAE-n have been reported, however, their clinical relevance is unclear. Here, we present a dataset on neuronal autoantibody profiles in ICI-treated cancer patients with and without irAE-n, which was generated to investigate the potential role of neuronal autoantibodies in ICI-induced autoimmunity. Between September 2017 and January 2022 serum samples of 29 cancer patients with irAE-n post-ICI treatment) and 44 cancer control patients without high-grade immune-related adverse events (irAEs, n = 44 pre- and post-ICI treatment) were collected and tested for a large panel of brain-reactive and neuromuscular autoantibodies using indirect immunofluorescence and immunoblot assays. Prevalence of autoantibodies was compared between the groups and correlated with clinical characteristics such as outcome and irAE-n manifestation. These data represent the first systematic comparison of neuronal autoantibody profiles between ICI-treated cancer patients with and without irAE-n, providing valuable information for both researchers and clinicians. In the future, this dataset may be valuable for meta-analyses on the prevalence of neuronal autoantibodies in cancer patients.

Synergistic effects of immune checkpoints and checkpoint inhibitors in inflammatory neuropathies: Implications and mechanisms

Immune checkpoint molecules play pivotal roles in the regulation of immune homeostasis. Disruption of the immune checkpoints causes autoimmune/inflammatory as well as malignant disorders. Over the past few years, the immune checkpoint molecules with inhibitory function emerged as potential therapeutic targets in oncological conditions. The inhibition of the function of these molecules by using immune checkpoint inhibitors (ICIs) has brought paradigmatic changes in cancer therapy due to their remarkable clinical benefits, not only in improving the quality of life but also in prolonging the survival time of cancer patients. Unfortunately, the ICIs soon turned out to be a "double-edged sword" as the use of ICIs caused multiple immune-related adverse effects (irAEs). The development of inflammatory neuropathies such as Guillain-Barré syndrome (GBS) and Chronic Inflammatory Demyelinating Polyradiculoneuropathy (CIDP) as the secondary effects of immunotherapy appeared very challenging as these conditions result in significant and often permanent disability. The underlying mechanism(s) through which ICIs trigger inflammatory neuropathies are currently not known. Compelling evidence suggests autoimmune reaction and/or inflammation as the independent risk mechanism of inflammatory neuropathies. There is a lack of understanding as to whether prior exposure to the risk factors of inflammatory neuropathies, the presence of germline genetic variants in immune function-related genes, genetic variations within immune checkpoint molecules, the existence of autoantibodies, and activated/memory T cells act as determining factors for ICI-induced inflammatory neuropathies. Herein, we highlight the available pieces of evidence, discuss the mechanistic basis, and propose a few testable hypotheses on inflammatory neuropathies as irAEs of immunotherapy.

Immune signatures of checkpoint inhibitor-induced autoimmunity-A focus on neurotoxicity

BACKGROUND

Neurologic immune-related adverse events (irAE-n) are rare but severe toxicities of immune checkpoint inhibitor (ICI) treatment. To overcome diagnostic and therapeutic challenges, a better mechanistic understanding of irAE-n is paramount.

METHODS

In this observational cohort study, we collected serum and peripheral blood samples from 34 consecutive cancer patients with irAE-n (during acute illness) and 49 cancer control patients without irAE-n (pre- and on-ICI treatment, n = 44 without high-grade irAEs, n = 5 with high-grade nonneurologic irAEs). Patients received either anti-programmed cell death protein (PD)-1 or anti-PD ligand-1 monotherapy or anti-PD-1/anti-cytotoxic T-lymphocyte-associated protein-4 combination therapy. Most common cancers were melanoma, lung cancer, and hepatocellular carcinoma. Peripheral blood immune profiling was performed using 48-marker single-cell mass cytometry and a multiplex cytokine assay.

RESULTS

During acute illness, patients with irAE-n presented higher frequencies of cluster of differentiation (CD)8+ effector memory type (EM-)1 and central memory (CM) T cells compared to controls without irAEs. Multiorgan immunotoxicities (neurologic + nonneurologic) were associated with higher CD8+ EM1 T cell counts. While there were no B cell changes in the overall cohort, we detected a marked decrease of IgD- CD11c+ CD21low and IgD- CD24+ CD21high B cells in a subgroup of patients with autoantibody-positive irAE-n. We further identified signatures indicative of enhanced chemotaxis and inflammation in irAE-n patients and discovered C-X-C motif chemokine ligand (CXCL)10 as a promising marker to diagnose high-grade immunotoxicities such as irAE-n.

CONCLUSIONS

We demonstrate profound and partly subgroup-specific immune cell dysregulation in irAE-n patients, which may guide future biomarker development and targeted treatment approaches.

Metabolic and Toxic Myelopathies

OBJECTIVE

This article reviews the clinical presentation, diagnostic evaluation, and treatment of metabolic and toxic myelopathies resulting from nutritional deficiencies, environmental and dietary toxins, drugs of abuse, systemic medical illnesses, and oncologic treatments.

LATEST DEVELOPMENTS

Increased use of bariatric surgery for obesity has led to higher incidences of deficiencies in nutrients such as vitamin B12 and copper, which can cause subacute combined degeneration. Myelopathies secondary to dietary toxins including konzo and lathyrism are likely to become more prevalent in the setting of climate change leading to drought and flooding. Although modern advances in radiation therapy techniques have reduced the incidence of radiation myelopathy, patients with cancer are living longer due to improved treatments and may require reirradiation that can increase the risk of this condition. Immune checkpoint inhibitors are increasingly used for the treatment of cancer and are associated with a wide variety of immune-mediated neurologic syndromes including myelitis.

ESSENTIAL POINTS

Metabolic and toxic causes should be considered in the diagnosis of myelopathy in patients with particular clinical syndromes, risk factors, and neuroimaging findings. Some of these conditions may be reversible if identified and treated early, requiring careful history, examination, and laboratory and radiologic evaluation for prompt diagnosis.

Mononeuritis multiplex following immune checkpoint inhibitors in malignant pleural mesothelioma

Introduction

Mononeuritis multiplex is frequently related to vasculitic neuropathy and has been reported only sporadically as an adverse event of immune checkpoint inhibitors.

Methods

Case series of three patients with mononeuritis multiplex-all with mesothelioma-identified in the databases of two French clinical networks (French Reference Center for Paraneoplastic Neurological Syndromes, Lyon; OncoNeuroTox, Paris; January 2015-October 2022) set up to collect and investigate n-irAEs on a nationwide level.

Results

Three patients (male; median age 86 years; range 72-88 years) had pleural mesothelioma and received 10, 4, and 6 cycles, respectively, of first-line nivolumab plus ipilimumab combined therapy. In patient 1, the neurological symptoms involved the median nerves, and in the other two patients, there was a more diffuse distribution; the symptoms were severe (common terminology criteria for adverse events, CTCAE grade 3) in all patients. Nerve conduction studies indicated mononeuritis multiplex in all patients. Peripheral nerve biopsy demonstrated necrotizing vasculitis in patients 1 and 3 and marked IgA deposition without inflammatory lesions in patient 2. Immune checkpoint inhibitors were permanently withdrawn, and corticosteroids were administered to all patients, leading to complete symptom regression (CTCAE grade 0, patient 2) or partial improvement (CTCAE grade 2, patients 1 and 3). During steroid tapering, patient 1 experienced symptom recurrence and spreading to other nerve territories (CTCAE grade 3); he improved 3 months after rituximab and cyclophosphamide administration.

Discussion

We report the occurrence of mononeuritis multiplex, a very rare adverse event of immune checkpoint inhibitors, in the three patients with mesothelioma. Clinicians must be aware of this severe, yet treatable adverse event.

Neurologic manifestations of autoimmunity with immune checkpoint inhibitors

Immune checkpoint inhibitors (ICIs) are cancer immunotherapies that enhance the body's own immune system to treat cancer. ICI treatment, however, can cause immune-related adverse events (irAEs) that can affect any organ, resulting in significant morbidity and mortality. Neurologic irAEs (nirAEs) are rare and can affect the peripheral nervous system more commonly than the central nervous system. Treatment is dependent on the severity of the neurologic manifestations and often includs discontinuation of the ICI and initiation of steroid therapy as the first line; other treatments have also been used. NirAEs and cardiac irAEs have higher fatality rates underlying the importance of early recognition and appropriate management. This chapter reviews the clinical manifestations of neurologic immune-related adverse events associated with ICI treatment as well as diagnostic and therapeutic modalities.

Neurological adverse events of immune checkpoint inhibitors and the development of paraneoplastic neurological syndromes

Immune checkpoint inhibitors, a class of oncological treatments that enhance antitumour immunity, can trigger neurological adverse events closely resembling paraneoplastic neurological syndromes. Unlike other neurological adverse events caused by these drugs, post-immune checkpoint inhibitor paraneoplastic neurological syndromes predominantly affect the CNS and are associated with neural antibodies and cancer types commonly found also in spontaneous paraneoplastic neurological syndromes. Furthermore, post-immune checkpoint inhibitor paraneoplastic neurological syndromes have poorer neurological outcomes than other neurological adverse events of immune checkpoint inhibitors. Early diagnosis and initiation of immunosuppressive therapy are likely to be crucial in preventing the accumulation of neurological disability. Importantly, the neural antibodies found in patients with post-immune checkpoint inhibitor paraneoplastic neurological syndromes are sometimes detected before treatment, indicating that these antibodies might help to predict the development of neurological adverse events. Experimental and clinical evidence suggests that post-immune checkpoint inhibitor paraneoplastic neurological syndromes probably share immunological features with spontaneous paraneoplastic syndromes. Hence, the study of post-immune checkpoint inhibitor paraneoplastic neurological syndromes can help in deciphering the immunopathogenesis of paraneoplastic neurological syndromes and in identifying novel therapeutic targets.

Pathogenicity of functionally activated PD-1+CD8+ cells and counterattacks by muscular PD-L1 through IFNγ in myositis

Programmed-cell-death 1 (PD-1) expression is associated not only with T-cell activation but with exhaustion. Specifically, PD-1+ T cells present an exhausted phenotype in conditions of chronic antigen exposure, such as tumor microenvironments and chronic viral infection. However, the immune status regarding exhaustion of PD-1+CD8+ T cells in chronic autoimmune diseases including idiopathic inflammatory myopathies (IIMs) remains unclear. We aimed to clarify the role of PD-1+CD8+ T cells and PD-1 ligand (PD-L1) in IIMs. We showed that PD-1+ cells infiltrated into PD-L1-expressing muscles in patients with IIMs and immune checkpoint inhibitor-related myopathy. According to the peripheral blood immunophenotyping, the PD-1+CD8+ cell proportions were comparable between the active and inactive patients. Of note, PD-1+CD8+ cells in the active patients highly expressed cytolytic molecules, indicating their activation, while PD-1-CD8+ cells expressed low levels of cytolytic molecules in the active and inactive patients. A part of PD-1+CD8+ cells expressed the HMG-box transcription factor TOX highly and presented the exhausted phenotype in the active patients. Among PD-1+CD4+ T cells, PD-1highCXCR5-CD45RO+CD4+ peripheral helper T cells were increased in the active patients. PD-L1-deficient mice developed severer C-protein-induced myositis (CIM), a model of polymyositis, with abundant infiltration of PD-1+CD8+ cells expressing cytolytic molecules than wild-type mice, indicating pathogenicity of the PD-1+CD8+ cells and the protective role of PD-L1. The deficiency of IFNγ, a general PD-L1-inducer, impaired muscular PD-L1 expression and exacerbated CIM, indicating IFNγ-dependent muscular PD-L1 regulation. IFNγ-induced PD-L1 on myotubes was protective in an established muscle injury model. In conclusion, PD-1+CD8+ T cells rather than PD-1-CD8+ T cells were a pathogenic subset of IIMs. Muscular PD-L1 was regulated by IFNγ and exerted protective properties in IIMs.

Plasma Exchange in Patients With Myositis due to Immune Checkpoint Inhibitor Therapy

ABSTRACT

Immune checkpoint inhibitors used to treat malignancies may lead to various immune-related adverse events (irAEs) including conditions such as myositis and myasthenia gravis (MG). Here, we describe 2 cases of myositis treated effectively with therapeutic plasma exchange (PLEX). A 64-year-old man with thymic cancer developed leg weakness and dyspnea 1 month after the second dose of nivolumab with moderate weakness in proximal and distal muscles, with elevated creatine kinase levels. Another 77-year-old man with Stage IIIB squamous cell carcinoma of the lung developed progressive proximal muscle weakness and became nonambulatory after cycle 2 of durvalumab with persistently high creatine kinase levels despite prednisone treatment. Electrophysiology revealed irritative myopathy without evidence of neuromuscular junction dysfunction and MG antibody testing was nonrevealing. With PLEX, both patients noticed rapid improvement in strength. PLEX in conjunction with other immunosuppressive agents can result in rapid improvement in irAE-myositis even in patients without associated MG.

Neurologic Complications of Cancer Immunotherapy

OBJECTIVE

Immunotherapeutic approaches have revolutionized cancer treatment with immune checkpoint inhibitors and adoptive T-cell therapy now approved to treat a variety of solid and hematologic malignancies. This article summarizes the distinctive neurologic side effects of these therapies as well as their management.

LATEST DEVELOPMENTS

Neurologic immune-related adverse events are rare but potentially serious complications of immune checkpoint inhibitors. Both peripheral and central nervous system disorders have been described, often necessitating a pause or cessation of immunotherapy. Immune effector cell-associated neurotoxicity syndrome is a potentially serious complication of chimeric antigen receptor T-cell therapy. While symptoms may be mild and self-limited, delirium, encephalopathy, seizures, focal neurologic deficits, and fulminant cerebral edema can be seen. Close neurologic monitoring is imperative. The mainstay of treatment for neurologic complications includes high-dose corticosteroids, although other immunomodulatory strategies may be used in severe or refractory cases.

ESSENTIAL POINTS

The spectrum of neurologic complications of cancer immunotherapy is broad, encompassing both central and peripheral nervous system disorders, indolent as well as fulminant clinical presentations, and wide-ranging severity with variable response to treatment. Early identification and multidisciplinary management are crucial to balance neurologic recovery and antitumor control.

Neurotoxicity of Cancer Immunotherapies Including CAR T Cell Therapy

PURPOSE OF REVIEW

To outline the spectrum of neurotoxicity seen with approved immunotherapies and in pivotal clinical trials including immune checkpoint inhibitors, chimeric antigen receptor T-cell therapy, vaccine therapy, and oncolytic viruses.

RECENT FINDINGS

There has been an exponential growth in new immunotherapies, which has transformed the landscape of oncology treatment. With more widespread use of cancer immunotherapies, there have also been advances in characterization of its associated neurotoxicity, research into potential underlying mechanisms, and development of management guidelines. Increasingly, there is also mounting interest in long-term neurologic sequelae. Neurologic complications of immunotherapy can impact every aspect of the central and peripheral nervous system. Early recognition and treatment are critical. Expanding indications for immunotherapy to solid and CNS tumors has led to new challenges, such as how to reliably distinguish neurotoxicity from disease progression. Our evolving understanding of immunotherapy neurotoxicity highlights important areas for future research and the need for novel immunomodulatory therapeutics.