Case Report: Limbic encephalitis following treatment with durvalumab for small-cell lung cancer

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.

Antibody-positive paraneoplastic neurological syndromes associated with immune checkpoint inhibitors: a systematic review

BACKGROUND AND OBJECTIVES

This study aimed to describe the clinical and prognostic characteristics of antibody-positive paraneoplastic neurological syndrome (PNS) associated with immune checkpoint inhibitors (ICIs).

METHODS

We conducted a systematic review of relevant publications in PubMed and Embase from inception to December 2023. Patients with positive anti-neuronal antibodies who had a definite, probable, or possible diagnosis of PNS based on the 2021 PNS-Care Score criteria were included.

RESULTS

A total of 76 records with 108 antibody-positive ICI-PNS patients were included in this systematic review. According to the updated 2021 criteria, 60.2% of patients were classified as definite PNS, 29.6% as probable PNS, and 10.2% as possible PNS. The median age was 66 years (range: 26-82), and 56.5% of patients were male. The most frequently associated tumors included lung cancer, melanoma, and Merkel cell carcinoma, and 72.2% of patients developed neurological symptoms within 6 months after ICIs treatment. The most common clinical phenotypes were limbic encephalitis (35.2%), rapidly progressive cerebellar syndrome (19.4%), and Lambert-Eaton myasthenic syndrome (13.0%), while the most common autoantibodies were anti-Hu (34.3%), anti-Ma2 (16.7%), and anti-P/Q VGCC (14.8%) antibodies. CSF inflammation was observed in 63.0% patients, predominantly lymphocytic. Corticosteroids were the mainstay of immunotherapy (90.9%), followed by intravenous immunoglobulin (IVIG) and plasma exchange. Outcome information was reported for 103 patients. The median follow-up was 4 months (IQR: 2, 10), and 56.3% of patients showed improvement, while 37.0% of patients died at the last follow-up. Patients with anti-Hu or  anti-Ma2 antibodies had a higher proportion of deterioration and mortality (P < 0.05).

CONCLUSION

Limbic encephalitis and anti-Hu antibody are relatively common in antibody-positive ICI-PNS, and most patients present with CSF inflammation. Discontinuation of ICIs and corticosteroids are the main treatments. High-risk antibodies may be a risk factor for an unfavorable prognosis, particularly anti-Hu and anti-Ma2 antibodies.

Immune checkpoint inhibitor-induced autoimmune limbic encephalitis with positivity for anti-Hu antibodies in a patient with small-cell lung cancer: A case report and literature review

In recent years, there has been an increasing number of studies on neurological symptoms induced as paraneoplastic neurological syndrome (PNS) or neurological immune-related adverse events (irAEs) in patients treated with immune checkpoint inhibitors (ICIs). Herein, we report a 68-year-old male patient with small-cell lung cancer who developed memory impairment and autonomic nervous system dysfunction after three courses of carboplatin, etoposide, and durvalumab therapy. Brain magnetic resonance imaging revealed hyperintense areas restricted to the bilateral temporal lobes. Moreover, based on the blood test results, the patient was strongly positive for anti-neuronal nuclear antibodies. Hence, he was diagnosed with autoimmune limbic encephalitis (ALE). Corticosteroid pulse therapy was administered. After treatment, the patient exhibited gradual improvement in memory impairment. However, while tapering the prednisolone dose, the patient exhibited relapse of memory disturbance owing to ALE. It is challenging to distinguish PNS from neurological irAEs. However, ICI-induced ALE with positivity for anti-Hu antibodies has an extremely poor prognosis.

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.

Uncommon Adverse Events of Immune Checkpoint Inhibitors in Small Cell Lung Cancer: A Systematic Review of Case Reports

BACKGROUND

This study aimed to systematically review case reports documenting rare adverse events in patients with small cell lung cancer (SCLC) following the administration of immune checkpoint inhibitors (ICIs).

METHODS

A systematic literature review was conducted to identify case reports detailing previously unreported adverse drug reactions to ICIs in patients with SCLC. The scope of the literature reviewed was restricted to case studies on SCLC published up to 31 December 2023.

RESULTS

We analyzed twenty-four studies on ICI use for patients with SCLC. There were six reports on atezolizumab, four on durvalumab, and three on adverse events from monotherapy with nivolumab. Reports involving combination treatments were the most frequent, with a total of six, predominantly involving using nivolumab in combination with ipilimumab. Additionally, there was one report each on using pembrolizumab, nofazinilimab, sintilimab, tislelizumab, and toripalimab. We collected detailed information on the clinical course, including patient and disease characteristics, symptoms, treatment for each adverse event, and recovery status. Among the patients included in the case reports, 21 out of 24 (87.5%) had extensive-stage SCLC when initiating ICI therapy, with only 1 patient diagnosed with limited-stage SCLC. Respiratory system adverse events were most common, with seven cases, followed by neurological, endocrinological, and gastroenterological events. Three case reports documented adverse events across multiple systems in a single patient. In most cases, patients showed symptom improvement; however, four studies reported cases where patients either expired without symptom improvement or experienced sequelae.

CONCLUSIONS

Efforts to develop reliable biomarkers for predicting irAEs continue, with ongoing research to enhance predictive precision. Immunotherapy presents diverse and unpredictable adverse events, underscoring the need for advanced diagnostic tools and a multidisciplinary approach to improve patient management.

Paraneoplastic Neurological Syndromes as Initial Presentation of Tumors: An Eight-Year Single-Center Experience

BACKGROUND

Paraneoplastic Neurological Syndromes (PNS) comprise a diverse group of disorders propagated by immune-mediated effects of malignant tumors on neural tissue.

METHODS

A single-center longitudinal study was performed including consecutive adult patients treated at a tertiary academic hospital between 2015 and 2023 and diagnosed with PNS. PNS were ascertained using the 2004 and the revised 2021 PNS-Care diagnostic criteria.

RESULTS

Thirteen patients who fulfilled the 2004 definite PNS criteria were included. PNS comprise diverse neurological syndromes, with neuromuscular junction disorders (54%) and limbic encephalitis (31%) being predominant. PNS-related antibodies were detected in 85% of cases, including anti-AChR (n = 4), anti-P/Q-VGCC (n = 3), anti-Hu (n = 3), anti-Yo (n = 1), anti-Ma (n = 1), anti-titin (n = 1), anti-IgLON5 (n = 1), and anti-GAD65 (n = 1). Thymoma (31%), small-cell lung cancer (23%), and papillary thyroid carcinoma (18%) were the most frequent tumors. Imaging abnormalities were evident in 33% of cases. Early immunotherapy within 4-weeks from symptom onset was associated with favorable outcomes. At a mean follow-up of 2 ± 1 years, two patients with anti-Hu and anti-Yo antibodies died (18%). Four and three patients fulfilled the 2021 PNS-Care diagnostic criteria for definite and probable PNS, respectively.

CONCLUSIONS

This study highlights the clinical heterogeneity of PNS, emphasizing the need for early suspicion and prompt treatment initiation for optimal outcomes.