Cytokine release syndrome caused by immune checkpoint inhibitors: a case report and literature review.

1.
Introduction
Immune checkpoint inhibitors (ICIs) are a new approach in cancer immunotherapy [1]. This therapy works by blocking the inhibitory effects of tumor cells on T cells, thereby reducing the immune system’s tolerance to tumor cells and enhancing T cells’ ability to effectively recognize and eliminate these cells [2]. Compared with traditional chemotherapy, the combination of tislelizumab with chemotherapy not only improves the survival rate of patients with advanced gastric/gastroesophageal junction (G/GEJ) adenocarcinoma but also extends their survival time [3]. Currently, the efficacy of PD-1 inhibitors as monotherapy for patients with advanced gastric cancer (GC) has been confirmed and is supported by multiple studies. However, 30–60% of patients still do not respond to PD-1 inhibitors, which may be related to factors such as T cell exclusion or exhaustion, insufficient T cell trafficking, and the accumulation of various immunosuppressive factors within the tumor microenvironment [4]. Cytokine release syndrome (CRS) is a systemic inflammatory response triggered by various factors, including infections and different forms of immunotherapy. CRS constitutes one of the most frequent severe adverse reactions associated with immunotherapy involving T cells (including bispecific antibody and chimeric antigen receptor T cell therapy). While CRS can also occur in patients receiving ICIs, its rarity is reflected in the limited number of scattered case reports [5,6]. Currently, there are no diagnostic standards or treatment guidelines for CRS induced by ICIs [6], which poses challenges for diagnosis and treatment. The clinical manifestations of CRS can easily be mistaken for infections or other ailments, potentially leading to diagnostic oversights and misdiagnosis. Therefore, enhancing clinicians’ comprehension of ICI-induced CRS becomes imperative. This study presents a case report of a patient treated at Zhongshan Hospital, affiliated with Fudan University, who developed CRS following the administration of ICIs.

2.
Case introduction
A 76-year-old male patient, height: 165 cm, weight: 50 kg, body surface area: 1.51 m2, presented on 10 June 2022, with the onset of nausea and vomiting. On 17 June 2022, Gastroscopy suggested: a giant ulcer of the gastric body, about 5 × 3 cm in size; Pathology indicted low-differentiated adenocarcinoma (of the gastric body) with elevated AFP; Immunohistochemistry: AFP (+), Claudin18.2 (-), EBER (-), Her-2 (-), Ki-67 (80% positive), Met (100%+), MLH1 (+), MSH2 (+), MSH6 (+), PMS2 (+), PD-1 (-), PD-L1 (-). 18F-FDG PET/CT showed: a malignant tumor of the gastric body invading the peripheral fat interstitial space, accompanied by multiple lymph node metastases in the intra-abdominal cavity, retroperitoneum, posterior diaphragm pedicle, mediastinum and bilateral clavicular region, liver metastases and plantation metastases in the abdominal and pelvic cavities with effusion. AJCC Staging: cT3N2M1, stage IV. The patient and his family had no history of autoimmune disease nor other immunological disorders. On 27 June 2022, gastric artery embolization was performed, with intraoperative administration of oxaliplatin 100 mg and irinotecan 100 mg. On 28 June 2022 tumor markers: AFP:34332.0 ng/ml; on 23 July 2022, 18 August 2022 and 10 September 2022, the patient received three completed cycles of therapy with a combination of PD-1 inhibitor, anlotinib and combination of capecitabine (xeloda) and oxaliplatin (XELOX) during the first-line therapy cycles: tislelizumab 200 mg d1+ anlotinib 8 mg d1–14 po+ oxaliplatin 200 mg (130 mg/m2) d1+ capecitabine 1500 mg (1000 mg/m2) bid d1–14, q3w. Partial response (PR) was evaluated on 29 September 2022 (Figure 1). Biomarker: AFP:502 ng/ml (normal reference range <20 ng/ml); (Figure 2); 19 days after the third dose of therapy, the patient experienced sudden unconsciousness, frothing at the mouth, and the convulsion lasted for 1 min, which relieved spontaneously. The blood oxygen saturation was 94%, the blood pressure was 150/90 mmHg (1 mmHg = 0.133 kpa), the heart rate was 98 bpm, and the respiratory rate was 35 breaths/min. Of 14 proinflammatory and regulatory cytokines and chemokines evaluated, interleukin (IL)-17A, tumor necrosis factor alpha (TNF-α), interferon gamma (IFN-γ), IL-6 and IL-8 were increased at CRS onset (Table 1). Systemic inflammatory markers CRP and ferritin were also increased at CRS onset (Table 2). EEG: mildly abnormal, with full lead slow waves. Plain CT scan of the head: scattered ischemic infarct foci, partial softening foci and aged brain. Cranial MR plain scan: multiple cerebral infarct ischemic foci (some old and softened), old brain. In terms of treatment, there was limited amelioration of symptoms after mannitol treatment from 30 September 2022. Considering the epileptic-like clinical manifestations, acute systemic inflammatory response syndrome, and elevated ferritin levels, the diagnosis of immune-related adverse reaction CRS is confirmed. Starting from 1 October 2022, the patient was treated with 50 mg of methylprednisolone (1 mg/kg) once daily for 7 consecutive days, and intravenous immunoglobulin 20 g (0.4 g/kg) once daily for 5 consecutive days. The patient did not experience subsequent seizure episodes thereafter, and inflammatory indicators, ferritin and cytokines gradually decreased. Expectedly, the aberrantly activated immune response partly returned to balance at CRS resolution. It was recommended to pursue further evaluation through lumbar puncture; however, the patient declined the procedure. Subsequent to this decision, systemic antitumor treatment was discontinued, and died clinically on 31 January 2023 (Figure 3).

3.
Discussion
CRS is a phenomenon of excessive immune activation in immunotherapy, characterized by a large release of cytokines leading to a systemic inflammatory syndrome. Among immune-related adverse events (irAEs) caused by PD-1 inhibitors, the incidence of CRS is less than 0.01% [7]. This article introduces a case of CRS induced by the administration of tislelizumab. The patient exhibited pronounced symptoms including altered consciousness, frothing at the mouth, convulsions and other epileptiform episodes. Despite inadequate response to dehydration therapy, notable improvement occurred subsequent to glucocorticoid and intravenous gamma globulin intervention. Clinical CRS manifestations encompass fever, fatigue, headache, seizures, nausea, chills, myalgia, dyspnea, hypotension, tachycardia, as well as hepatic and renal impairment, along with acute respiratory distress syndrome. The first reports of CRS emerged in the context of chimeric antigen receptor T cell therapy, characterized by rapid T lymphocyte expansion and substantial release of inflammatory cytokines. Key cytokines include IL-1β, IL-6, IL-17, TNF-α and IFN-γ. Since its identification, CRS has been documented not only in cases involving ICIs treatment but also in severe infection scenarios [8–10].
The severity of CRS is closely related to the levels of inflammatory cytokines and their receptors [11]. CRS is characterized by the excessive secretion of inflammatory cytokines by various inflammatory cells, such as B lymphocytes, T lymphocytes and natural killer cells, including TNF, IL-6, IL-5, IL-1, IL-10, IFN-γ and transforming growth factor, with IL-6 playing a particularly significant role as a key factor in the development of inflammatory toxicity [12]. Moreover, CRS induces heightened cytokine secretion upon interaction with endothelial cells, monocytes, macrophages and dendritic cells, thereby exacerbating various symptoms and eliciting varying degrees of organ impairment [13]. Notably, severe CRS may lead to abnormal elevation of systemic inflammatory markers, such as high-sensitivity CRP and ferritin [14].
Cytokines are of great interest due to their wide range of biological functions. They can contribute to the pathophysiology of irAEs by mediating a decrease in self-tolerance, and they can also be involved in the anti-tumor effects of ICIs by enhancing the activation of cytotoxic T cells [15]. Recent studies [16–18] have gradually confirmed the correlation between irAEs and treatment efficacy, following the observation by Downey et al. [19] that melanoma patients treated with PD-1 inhibitors who experienced irAEs had better treatment outcomes. Multiple studies [20–22] have shown that patients with irAEs have significantly better progression-free survival compared with those without irAEs. In this case, the patient’s serum predominantly showed an upregulation of Th1-type cytokines (IL-2, IFN-γ and IL-8), which play a positive role in anti-tumor immunity. Despite severe CRS following immunotherapy, the treatment effect was evaluated as PR, and after cessation of antitumor therapy, serum tumor markers continued to decline with prolonged efficacy. This is consistent with literature reports. However, disease progression and eventual death occurred after stopping systemic anti-tumor treatment.
It should be noted that not all types of irAEs are associated with the efficacy of ICIs. For instance, skin toxicity or endocrine toxicity often indicates better efficacy [23,24] and prognosis, while the relationship between other types of irAEs and treatment efficacy remains unclear [21]. Future prospective studies with larger sample sizes are anticipated to further explore this relationship.
In terms of CRS diagnosis, FAJ-GENBAUM et al. [10] proposed three evaluation criteria: elevated levels of circulating cytokines; acute systemic inflammatory response syndrome; secondary organ dysfunction ( typically involving the kidneys, liver or lungs). A definition of systemic inflammatory response syndrome (SIRS) [25] requires meeting any two of the following criteria: temperature exceeding 38°C or below 36°C; 2) heart rate greater than 90 beats per min; respiratory rate greater than 20 breaths per min or CO2 pressure less than 32 mmHg; white blood cell count greater than 12,000 or less than 4000/ml, or the proportion of neutrophil bands greater than 10%.
The clinical manifestations of CRS may meet the diagnostic criteria for SIRS. In this case, the clinical symptoms included altered consciousness, frothing at the mouth and convulsive epileptic-like seizures, along with elevated circulating cytokine levels (such as IL-6, IL-10, TNF-α and IFN-γ), combined with SIRS and significantly elevated ferritin, all of which are consistent with CRS. Therefore, patients who exhibit SIRS symptoms after receiving ICIs should be monitored closely for the possibility of CRS.
The 2018 American ASBMT consensus defines CRS as a supraphysiological response that causes the activation or participation of endogenous or infused T cells or other immunological effector cells after immunotherapy [26]. Clinically, it needs to be differentiated from tumor progression, infection, immune encephalitis, etc. In the context of this case, both cranial CT and MR scans failed to reveal intracranial tumor metastasis. Assessment of tumor PR was executed via enhanced CT scans of the chest, abdomen, and pelvis. There were no clinical manifestations indicative of infection such as fever, fear of cold, chills, etc. during the course of the disease. Therefore, there was insufficient evidence of tumor progression and infection. In addition the patient was treated with a combination of chemotherapeutic agents and targeted agents, which needs to be differentiated from drug related reversible posterior leukoencephalopathy syndrome (RPLS). RPLS has been reported in the literature to be induced by oxaliplatin and anlotinib [27,28], with signs and symptoms including headache, altered mental status, seizures and altered visual function with or without hypertension [29–31]. CT can detect cerebral edema due to RPLS, but cranial MRI is more sensitive, and the typical MRI manifestation of RPLS is bilateral parieto–occipital lobe predominantly vasogenic cerebral edema [29]. There was no cerebral edema manifestation in the cranial CT and MRI of our patient, so there was insufficient basis for encephalopathy caused by oxaliplatin and anlotinib. In concert with epileptiform clinical manifestations, prominent elevation in inflammatory response markers and ferritin levels was noted. The administration of glucocorticoids and intravenous gamma globulin was effective. Considering the lack of evidence substantiating infection as the cause, the clinical picture, coupled with treatment response, substantiated a CRS diagnosis. However, the patient, in this case, declined a lumbar puncture examination during the course of treatment, imaging studies showed no evidence of infection, thus impeding further clarification on the potential co-occurrence of immune encephalitis.
Therapeutically, steroid drugs are effective treatments for inhibiting excessive inflammatory responses and managing CRS. In cases of severe adverse reactions associated with immunotherapy, such as CRS and neurotoxicity, the administration of high-dose intravenous glucocorticoids is recommended at the earliest possible stage [32]. Additionally, when considering the potential necessity for prolonged steroid use, antibiotics can be used prophylactically to prevent opportunistic infections such as fungi. To avoid the rebound phenomenon, a gradual reduction In steroid dosage Is advisable. Current research has indicated that using glucocorticoids is very effective in treating CRS and neurotoxic reactions [33]. It may be the broad anti-inflammatory effects of high-dose glucocorticoids, coupled with their ability to penetrate the central nervous system, allowing direct treatment of neurotoxicity [34].
Given the pivotal role of cytokines in driving the pathology of CRS, they can be detected by using IL-6, IL-1, IFN-γ or TNF-α and other cytokine inhibitors to curb the cascade of cytokine signaling [22]. Tocilizumab, a recombinant humanized monoclonal antibody targeting the IL-6 receptor, is presently utilized primarily for the treatment of rheumatoid arthritis. However, a standardized treatment approach for ICIs-induced CRS has not yet been established. Most case reports use glucocorticoids [35] or glucocorticoids in combination with tocilizumab [5,36,37]. While some patients exhibit suboptimal responses to glucocorticoids, they respond well to tocilizumab [5]. At present, the US FDA has approved tocilizumab for the treatment of severe or life-threatening CRS [38]. In addition, studies have shown that anakinra, an IL-1 receptor antagonist, significantly reduces the occurrence of CRS and neurotoxicity during immunotherapy [39]. However, the dosages and courses of glucocorticoids and cytokine inhibitors are not yet standardized. In this particular case, a combination of glucocorticoids and intravenous gamma globulin was administered. The patient’s symptoms rapidly ameliorated, abnormal laboratory indicators significantly decreased, and cytokine inhibitors were not used. Following a 4 month cessation of antitumor therapy, the patient experienced a resurgence of tumor-related symptoms and ultimately deceased. The likelihood of tumor progression was considered a significant factor contributing to the cause of death.

4.
Conclusion
In conclusion, the administration of ICIs can incite CRS, a severe, rapidly progressing condition with a poor prognosis, demanding clinical attention.
CRS is a rare, yet potentially life-threatening adverse reaction observed during ICIs treatment. Currently, there are no established biomarkers to predict severe ICIs-induced CRS. Early diagnosis is key to effective treatment of CRS. However, due to the lack of specific clinical manifestations and the rapid progression of the condition, CRS is often misdiagnosed or diagnosed too late before patient death. Laboratory tests, including elevated levels of transaminases, lactate dehydrogenase and triglycerides, may be diagnostic features of CRS [40]. Elevated inflammatory markers, such as serum ferritin, are also typical characteristics of CRS [41]. In the era of immunotherapy, if clinical symptoms arise that cannot be attributed to tumor progression and are accompanied by a significant elevation in inflammatory markers, the possibility of CRS should be considered. In the treatment of CRS, the efficacy of singular therapeutic approaches is limited. With the emergence of multidisciplinary integrated treatments, the effectiveness of combined treatment strategies for CRS management has improved. However, exploring more effective treatment options for ICIs-induced CRS remains a crucial area of investigation.