68Ga-DOTATOC PET/CT to detect immune checkpoint inhibitor-related myocarditis

Complementary use of cardiac magnetic resonance and 18 F-FDG positron emission tomography imaging in suspected immune checkpoint inhibitor myocarditis

BACKGROUND

Immune checkpoint inhibitor (ICI) myocarditis is an uncommon but potentially fatal complication of immunotherapy. Cardiac imaging is essential to make timely diagnoses as there are critical downstream implications for patients.

OBJECTIVE

To determine the agreement of cardiac magnetic resonance (CMR) and 18 F-fluorodeoxyglucose Positron Emission Tomography (FDG-PET) in patients with suspected ICI myocarditis.

METHODS

Patients with suspected ICI myocarditis, who underwent CMR and 18 F-FDG-PET imaging at a single cardio-oncology service from 2017 to 2023, were enrolled. CMR was performed according to recommended guidelines for assessment of myocarditis. 18 F-FDG-PET imaging was performed following 18 h carbohydrate-free fast. Imaging was analysed by independent reviewers to determine the presence or absence of ICI myocarditis.

RESULTS

Twelve patients (mean age 60 ± 15 years old, 7 [58%] male) underwent both CMR and 18 F-FDG-PET imaging. Three (25%) met the 2018 Lake Louise Criteria for CMR diagnosis of myocarditis; 4 (33%) had evidence of myocardial inflammation as determined by 18 F-FDG-PET. Amongst those with positive 18 F-FDG-PET, mean standard uptake value (SUV) was 3.5 ± 1.7. There was agreement between CMR and PET in 7 cases (CMR and PET positive (n = 1), CMR and PET negative (n = 6)) and discordance in 5 cases (CMR positive and PET negative (n = 2), CMR negative and PET positive (n = 3)).

CONCLUSION

Both CMR and PET provide complementary clinical information in diagnostic of ICI myocarditis. CMR informs on myocardial oedema, whilst 18 F-FDG-PET provides information on glucose metabolism reflecting monocyte and lymphocytic activity. Future studies should investigate the role of hybrid PET-CMR for the timely diagnosis of ICI myocarditis.

Cardiovascular toxicity in antitumor therapy: biological and therapeutic insights

The evolution of antitumor therapies has significantly improved cancer prognosis but has concurrently resulted in cardiovascular toxicities. Understanding the biological mechanisms behind these toxicities is crucial for effective management. Immunotherapy-related cardiovascular toxicities are primarily mediated by immune cells and secreted cytokines. Chemotherapy may cause cardiovascular damage through autophagy disruption and mitochondrial dysfunction. Targeted therapies can induce toxicity through endothelin-1 (ET-1) production and cardiac signaling disruption. Radiotherapy may lead to cardiomyopathy and myocardial fibrosis by affecting endothelial cells, triggering inflammatory responses and accelerating atherosclerosis. This review provides insights into these mechanisms and strategies, aiming to enhance the clinical prevention and treatment of cardiovascular toxicities.

Factors Associated with Myocardial Uptake on Oncologic Somatostatin PET Investigations and Differentiation from Myocardial Uptake of Acute Myocarditis

Myocardial somatostatin PET uptake is observed not only in most patients with acute myocarditis (AM) but also in some oncology patients referred for routine somatostatin PET. This raises concerns about the specificity of somatostatin PET for detecting myocarditis. The current study aims to identify factors associated with the detection of myocardial uptake on somatostatin PET scans recorded for oncology indications and differential PET criteria that characterize myocardial uptake in AM patients. Methods: We analyzed factors associated with the detection of myocardial [68Ga]Ga-DOTATOC uptake in 508 [68Ga]Ga-DOTATOC PET scans from 178 patients, performed for confirmed or suspected oncologic disease (Onc-PET) and PET criteria that could differentiate myocardial [68Ga]Ga-DOTATOC uptake in 31 patients with MRI-ascertained AM (AM-PET) from that in the Onc-PET group. Results: Significant myocardial uptake was detected in 137 (26.9%) Onc-PET scans and was independently associated with somatostatin analog treatment (exp(β), 0.805; 95% CI, 0.728-0.890; P < 0.001) and age (exp(β), 1.005; 95% CI, 1.001-1.009; P = 0.012). A comparable model was selected for predicting the myocardial-to-blood SUVmax ratio using somatostatin analog treatment (P < 0.001) and history of coronary artery disease (P = 0.022). Myocardial uptake was detected in 12.9% (25/193) of Onc-PET scans from patients treated with somatostatin analogs but in 43.4% (59/136) of untreated patients over the median age of 64 y. Myocardial uptake was apparent in all 31 AM-PET scans, with volume and intensity of uptake dramatically higher than in the 137 Onc-PET scans showing myocardial uptake. A myocardial-to-blood SUVmax ratio threshold of 2.20 provided a sensitivity of 87% (27/31) and a specificity of 88% (44/50) for differentiating myocardial uptake between the AM-PET group and an Onc-PET group restricted to patients with clinical characteristics comparable to those of patients in the AM-PET group (≤64 y of age, no coronary artery disease history, and no somatostatin agonists). A myocardial uptake volume threshold of 18 cm3 provided comparable diagnostic accuracy (sensitivity, 84% [26/31]; specificity, 94% [47/50]). Conclusion: Myocardial uptake was detected in 26.9% of somatostatin PET scans recorded for oncology indications. This rate was decreased by somatostatin analog treatments and increased in older individuals. However, somatostatin PET scans, analyzed with the quantitative criterion of uptake intensity or volume, are able to identify AM and to differentiate it from myocardial uptake of other origins.

Novel tracers to assess myocardial inflammation with radionuclide imaging

Myocardial inflammation plays a central role in the pathophysiology of various cardiac diseases. While FDG-PET is currently the primary method for molecular imaging of myocardial inflammation, its effectiveness is hindered by physiological myocardial uptake as well as its propensity for uptake by multiple disease-specific mechanisms. Novel radiotracers targeting diverse inflammatory immune cells and molecular pathways may provide unique insight through the visualization of underlying mechanisms central to the pathogenesis of inflammatory cardiac diseases, offering opportunities for increased understanding of immunocardiology. Moreover, the potentially enhanced specificity may lead to better quantification of disease activity, aiding in the guidance and monitoring of immunomodulatory therapy. This review aims to provide an update on advancements in non-FDG radiotracers for imaging myocardial inflammatory diseases, with a focus on cardiac sarcoidosis, myocarditis, and acute myocardial infarction.

Immune-Related Adverse Events Induced by Immune Checkpoint Inhibitors and CAR-T Cell Therapy: A Comprehensive Imaging-Based Review

Immunotherapy has revolutionized oncology care, improving patient outcomes in several cancers. However, these therapies are also associated with typical immune-related adverse events due to the enhanced inflammatory and immune response. These toxicities can arise at any time during treatment but are more frequent within the first few months. Any organ and tissue can be affected, ranging from mild to life-threatening. While some manifestations are common and more often mild, such as dermatitis and colitis, others are rarer and more severe, such as myocarditis. Management depends on the severity, with treatment being held for >grade 2 toxicities. Steroids are used in more severe cases, and immunosuppressive treatment may be considered for non-responsive toxicities, along with specific organ support. A multidisciplinary approach is mandatory for prompt identification and management. The diagnosis is primarily of exclusion. It often relies on imaging features, and, when possible, cytologic and/or pathological analyses are performed for confirmation. In case of clinical suspicion, imaging is required to assess the presence, extent, and features of abnormalities and to evoke and rule out differential diagnoses. This imaging-based review illustrates the diverse system-specific toxicities associated with immune checkpoint inhibitors and chimeric antigen receptor T-cells with a multidisciplinary perspective. Clinical characteristics, imaging features, cytological and histological patterns, as well as the management approach, are presented with insights into radiological tips to distinguish these toxicities from the most important differential diagnoses and mimickers-including tumor progression, pseudoprogression, inflammation, and infection-to guide imaging and clinical specialists in the pathway of diagnosing immune-related adverse events.

STING-Targeted PET Imaging for Specific Detection and Therapeutic Monitoring of Myocarditis

Imaging strategies for the specific detection and therapeutic monitoring of myocarditis are still lacking. Stimulator of interferon genes (STING) is a signal transduction molecule involved in an innate immune response. Here, we evaluated the feasibility of the recently developed STING-targeted radiotracer [18F]FBTA for positron emission tomography (PET) imaging to detect myocardial inflammation and monitor treatment in myocarditis mice. [18F]FBTA-PET imaging was performed in myocarditis mice and normal mice to verify the specificity of [18F]FBTA for the diagnosis of myocarditis. We also performed PET imaging in mice with myocarditis treated to verify the ability of [18F]FBTA in therapeutic monitoring. The expression of STING and inflammatory cell types was confirmed by flow cytometry and immunohistochemistry. [18F]FDG-PET imaging of myocarditis was used as a contrast. [18F]FBTA-PET imaging showed that the average radioactive uptake was significantly higher in the hearts of the myocarditis group than in the control group. STING was highly overexpressed in cardiac inflammatory cells, including macrophages, dendritic cells (DCs), and T cells. However, there was no significant difference in cardiac radiotracer uptake of [18F]FDG between the myocarditis group and the control group. Moreover, cardiac uptake of [18F]FBTA was significantly reduced in cyclosporin A-treated myocarditis mice and myocardial STING expression was also significantly reduced after the treatment. Overall, we showed that a STING-targeted PET tracer [18F]FBTA can be used to monitor changes in the inflammatory microenvironment in myocarditis. Besides, [18F]FBTA-PET is also suitable for real-time monitoring of myocarditis treatment, representing a promising diagnostic and therapeutic monitoring approach for myocarditis.

PET/CT Imaging of Infectious Diseases: Overview of Novel Radiopharmaceuticals

Infectious diseases represent one of the most common causes of hospital admission worldwide. The diagnostic work-up requires a complex clinical approach, including laboratory data, CT and MRI, other imaging tools, and microbiologic cultures. PET/CT with 18F-FDG can support the clinical diagnosis, allowing visualization of increased glucose metabolism in activated macrophages and monocytes; this tracer presents limits in differentiating between aseptic inflammation and infection. Novel PET radiopharmaceuticals have been developed to overcome these limits; 11C/18F-labeled bacterial agents, several 68Ga-labeled molecules, and white blood cells labeled with 18F-FDG are emerging PET tracers under study, showing interesting preliminary results. The best choice among these tracers can be unclear. This overview aims to discuss the most common diagnostic applications of 18F-FDG PET/CT in infectious diseases and, as a counterpoint, to describe and debate the advantages and peculiarities of the latest PET radiopharmaceuticals in the field of infectious diseases, which will probably improve the diagnosis and prognostic stratification of patients with active infectious diseases.

Cardiovascular toxicity of immune therapies for cancer

In addition to conventional chemoradiation and targeted cancer therapy, the use of immune based therapies, specifically immune checkpoint inhibitors (ICIs) and chimeric antigen receptor T cell therapy (CAR-T), has increased exponentially across a wide spectrum of cancers. This has been paralleled by recognition of off-target immune related adverse events that can affect almost any organ system including the cardiovascular system. The use of ICIs has been associated with myocarditis, a less common but highly fatal adverse effect, pericarditis and pericardial effusions, vasculitis, thromboembolism, and potentially accelerated atherosclerosis. CAR-T resulting in a systemic cytokine release syndrome has been associated with myriad cardiovascular consequences including arrhythmias, myocardial infarction, and heart failure. This review summarizes the current state of knowledge regarding adverse cardiovascular effects associated with ICIs and CAR-T.

Immune checkpoint inhibitor-related myositis and myocarditis: diagnostic pitfalls and imaging contribution in a real-world, institutional case series

BACKGROUND

Immune checkpoint inhibitors (ICIs) are reshaping the prognosis of many cancers, but often cause immune-related adverse events (irAEs). Among neurological irAEs, myositis is the most frequently reported. Our aim is to describe clinical and non-clinical characteristics, treatment and outcome of all irMyositis (skeletal limb-girdle and/or ocular myositis) and irMyocarditis cases in our reference center.

METHODS

We retrospectively enrolled all irMyositis/irMyocarditis patients seen between 2018 and 2022. We reviewed demographics, clinical characteristics, biological, neurophysiological, imaging workup, treatment and outcome.

RESULTS

We included 14 consecutive patients. The most frequent treatments were pembrolizumab (35%) or ipilimumab-nivolumab combination (35%). Limb-girdle, ocular (non-fluctuating palpebral ptosis and/or diplopia with or without ophthalmoparesis) and cardiac phenotypes were equally distributed, overlapping in 40% of cases. Ocular involvement was frequently misdiagnosed; review of brain MRIs disclosed initially missed signs of skeletal myositis in one patient and ocular myositis in 3. Seven patients had other co-existing irAEs. When performed, myography showed a myogenic pattern. CK was elevated in 8/15 patients, troponin-T in 12/12 and troponin-I in 7/9 tested patients. ICI were discontinued in all cases, with further immunosuppressive treatment in nine patients. In most cases, neurological and cardiological outcome was good at last follow-up.

CONCLUSION

Myositis is a potentially severe irAE. Despite its heterogeneous presentation, some highly suggestive clinical symptoms, such as ocular involvement, or radiological signs should raise physicians' attention to avoid misdiagnosis. We thus recommend a multidisciplinary assessment (including complete neuromuscular evaluation) even in case of isolated myocarditis. Our series underlines the importance of an early diagnosis, since suspension of ICI and adequate treatment are usually associated with good functional outcome.

CD40 is an immune checkpoint regulator that potentiates myocardial inflammation through activation and expansion of CCR2 + macrophages and CD8 T-cells

Novel immune checkpoint therapeutics including CD40 agonists have tremendous promise to elicit antitumor responses in patients resistant to current therapies. Conventional immune checkpoint inhibitors (PD-1/PD-L1, CTLA-4 antagonists) are associated with serious adverse cardiac events including life-threatening myocarditis. However, little is known regarding the potential for CD40 agonists to trigger myocardial inflammation or myocarditis. Here, we leveraged genetic mouse models, single cell sequencing, and cell depletion studies to demonstrate that an anti-CD40 agonist antibody reshapes the cardiac immune landscape through activation of CCR2 + macrophages and subsequent recruitment of effector memory CD8 T-cells. We identify a positive feedback loop between CCR2 + macrophages and CD8 T-cells driven by IL12b, TNF, and IFN-γ signaling that promotes myocardial inflammation and show that prior exposure to CD40 agonists sensitizes the heart to secondary insults and accelerates LV remodeling. Collectively, these findings highlight the potential for CD40 agonists to promote myocardial inflammation and potentiate heart failure pathogenesis.

Expansion of Pathogenic Cardiac Macrophages in Immune Checkpoint Inhibitor Myocarditis

BACKGROUND

Immune checkpoint inhibitors (ICIs), antibodies targeting PD-1 (programmed cell death protein 1)/PD-L1 (programmed death-ligand 1) or CTLA4 (cytotoxic T-lymphocyte-associated protein 4), have revolutionized cancer management but are associated with devastating immune-related adverse events including myocarditis. The main risk factor for ICI myocarditis is the use of combination PD-1 and CTLA4 inhibition. ICI myocarditis is often fulminant and is pathologically characterized by myocardial infiltration of T lymphocytes and macrophages. Although much has been learned about the role of T-cells in ICI myocarditis, little is understood about the identity, transcriptional diversity, and functions of infiltrating macrophages.

METHODS

We used an established murine ICI myocarditis model (Ctla4+/-Pdcd1-/- mice) to explore the cardiac immune landscape using single-cell RNA-sequencing, immunostaining, flow cytometry, in situ RNA hybridization, molecular imaging, and antibody neutralization studies.

RESULTS

We observed marked increases in CCR2 (C-C chemokine receptor type 2)+ monocyte-derived macrophages and CD8+ T-cells in this model. The macrophage compartment was heterogeneous and displayed marked enrichment in an inflammatory CCR2+ subpopulation highly expressing Cxcl9 (chemokine [C-X-C motif] ligand 9), Cxcl10 (chemokine [C-X-C motif] ligand 10), Gbp2b (interferon-induced guanylate-binding protein 2b), and Fcgr4 (Fc receptor, IgG, low affinity IV) that originated from CCR2+ monocytes. It is important that a similar macrophage population expressing CXCL9, CXCL10, and CD16α (human homologue of mouse FcgR4) was expanded in patients with ICI myocarditis. In silico prediction of cell-cell communication suggested interactions between T-cells and Cxcl9+Cxcl10+ macrophages via IFN-γ (interferon gamma) and CXCR3 (CXC chemokine receptor 3) signaling pathways. Depleting CD8+ T-cells or macrophages and blockade of IFN-γ signaling blunted the expansion of Cxcl9+Cxcl10+ macrophages in the heart and attenuated myocarditis, suggesting that this interaction was necessary for disease pathogenesis.

CONCLUSIONS

These data demonstrate that ICI myocarditis is associated with the expansion of a specific population of IFN-γ-induced inflammatory macrophages and suggest the possibility that IFN-γ blockade may be considered as a treatment option for this devastating condition.

Cardiovascular Imaging in Contemporary Cardio-Oncology: A Scientific Statement From the American Heart Association

Advances in cancer therapeutics have led to dramatic improvements in survival, now inclusive of nearly 20 million patients and rising. However, cardiovascular toxicities associated with specific cancer therapeutics adversely affect the outcomes of patients with cancer. Advances in cardiovascular imaging have solidified the critical role for robust methods for detecting, monitoring, and prognosticating cardiac risk among patients with cancer. However, decentralized evaluations have led to a lack of consensus on the optimal uses of imaging in contemporary cancer treatment (eg, immunotherapy, targeted, or biological therapy) settings. Similarly, available isolated preclinical and clinical studies have provided incomplete insights into the effectiveness of multiple modalities for cardiovascular imaging in cancer care. The aims of this scientific statement are to define the current state of evidence for cardiovascular imaging in the cancer treatment and survivorship settings and to propose novel methodological approaches to inform the optimal application of cardiovascular imaging in future clinical trials and registries. We also propose an evidence-based integrated approach to the use of cardiovascular imaging in routine clinical settings. This scientific statement summarizes and clarifies available evidence while providing guidance on the optimal uses of multimodality cardiovascular imaging in the era of emerging anticancer therapies.

Cardiovascular Toxicity Associated With Immune Checkpoint Inhibitor Therapy: A Comprehensive Review

Immune checkpoint inhibitors (ICIs), a significant breakthrough treatment of cancer, exert their function through enhancing the immune system's ability to recognize and attack cancer cells. However, these revolutionary cancer treatments have been associated with a range of immune-related adverse effects, including cardiovascular toxicity. The most commonly reported cardiovascular toxicities associated with ICIs are myocarditis, pericarditis, arrhythmias, and vasculitis. These cardiovascular manifestations are often severe and can lead to life-threatening complications. Therefore, prompt identification and management of these toxicities is critical, and a multidisciplinary teamwork by cardiologists and oncologists are required to ensure optimal patient outcomes. In this review, we summarize the current knowledge on the mechanisms underlying ICI-associated cardiovascular toxicity, clinical presentations of these toxicities, potential risk factors, diagnosis, management, and surveillance strategies during ICI therapy. While ICIs have already transformed cancer treatment, further research is needed to better understand and manage their immune-related cardiovascular effects, and possibly, to identify biomarkers which can predict the occurrence of these cardiovascular complications.

Effects of immune-related adverse events (irAEs) and their treatment on antitumor immune responses

Immune checkpoint inhibitors (ICIs) are potentially life-saving cancer therapies that can trigger immune-related adverse events (irAEs). irAEs can impact any organ and range in their presentation from mild side effects to life-threatening complications. The relationship between irAEs and antitumor immune responses is nuanced and may depend on the irAE organ, the tumor histology, and the patient. While some irAEs likely represent an immune response against antigens shared between tumor cells and healthy tissues, other irAEs may be entirely unrelated to antitumor immune responses. Clinical observations suggest that low-grade irAEs have a positive association with responses to ICIs, but the correlation between severe irAEs and clinical benefit is less clear. Currently, severe irAEs are typically treated by interrupting or permanently discontinuing ICI treatment and administering empirically selected systemic immunosuppressive agents. However, these interventions could potentially diminish the antitumor effects of ICIs. Efforts to understand the mechanistic relationship between irAEs and the tumor microenvironment have yielded meaningful insights and nominated therapeutic targets for irAE management that may preserve or even boost ICI efficacy. We explore the clinical and molecular relationship between irAEs and antitumor immunity as well as the role that irAE treatments may play in shaping antitumor immune responses.

Mediators and mechanisms of immune checkpoint inhibitor-associated myocarditis: Insights from mouse and human

The broad application of immune checkpoint inhibitors (ICIs) has led to significant gains in cancer outcomes. By abrogating inhibitory signals, ICIs promote T cell targeting of cancer cells but can frequently trigger autoimmune manifestations, termed immune-related adverse events (irAEs), affecting essentially any organ system. Among cardiovascular irAEs, immune-related myocarditis (irMyocarditis) is the most described and carries the highest morbidity. The currently recommended treatment for irMyocarditis is potent immunosuppression with corticosteroids and other agents, but this has limited evidence basis. The cellular pathophysiology of irMyocarditis remains poorly understood, though mouse models and human data have both implicated effector CD8+ T cells, some of which are specific for the cardiomyocyte protein α-myosin. While the driving molecular signals and transcriptional programs are not well defined, the involvement of chemokine receptors such as CCR5 and CXCR3 has been proposed. Fundamental questions regarding why only approximately 1% of ICI recipients develop irMyocarditis and why irMyocarditis carries a much worse prognosis than other forms of lymphocytic myocarditis remain unanswered. Further work in both murine systems and with human samples are needed to identify better tools for diagnosis, risk-stratification, and treatment.

Tales from the future-nuclear cardio-oncology, from prediction to diagnosis and monitoring

Cancer and cardiovascular diseases (CVD) often share common risk factors, and patients with CVD who develop cancer are at high risk of experiencing major adverse cardiovascular events. Additionally, cancer treatment can induce short- and long-term adverse cardiovascular events. Given the improvement in oncological patients' prognosis, the burden in this vulnerable population is slowly shifting towards increased cardiovascular mortality. Consequently, the field of cardio-oncology is steadily expanding, prompting the need for new markers to stratify and monitor the cardiovascular risk in oncological patients before, during, and after the completion of treatment. Advanced non-invasive cardiac imaging has raised great interest in the early detection of CVD and cardiotoxicity in oncological patients. Nuclear medicine has long been a pivotal exam to robustly assess and monitor the cardiac function of patients undergoing potentially cardiotoxic chemotherapies. In addition, recent radiotracers have shown great interest in the early detection of cancer-treatment-related cardiotoxicity. In this review, we summarize the current and emerging nuclear cardiology tools that can help identify cardiotoxicity and assess the cardiovascular risk in patients undergoing cancer treatments and discuss the specific role of nuclear cardiology alongside other non-invasive imaging techniques.

The Role of Advanced Cardiovascular Imaging Modalities in Cardio-Oncology: From Early Detection to Unravelling Mechanisms of Cardiotoxicity

Advances in cancer therapies have led to a global improvement in patient survival rates. Nevertheless, the price to pay is a concomitant increase in cardiovascular (CV) morbidity and mortality in this population. Increased inflammation and disturbances of the immune system are shared by both cancer and CV diseases. Immunological effects of anti-cancer treatments occur with both conventional chemotherapy and, to a greater extent, with novel biological therapies such as immunotherapy. For these reasons, there is growing interest in the immune system and its potential role at the molecular level in determining cardiotoxicity. Early recognition of these detrimental effects could help in identifying patients at risk and improve their oncological management. Non-invasive imaging already plays a key role in evaluating baseline CV risk and in detecting even subclinical cardiac dysfunction during surveillance. The aim of this review is to highlight the role of advanced cardiovascular imaging techniques in the detection and management of cardiovascular complications related to cancer treatment.

Immune checkpoint inhibitor-related myocarditis: current understanding and potential diagnostic and therapeutic strategies

INTRODUCTION

Myocarditis associated with immune checkpoint inhibitors presents with an often-severe clinical phenotype with arrhythmias and concurrent myositis. This condition tends to occur early after treatment onset and is associated with a high fatality rate. Diagnosis may be challenging, and treatment algorithms are still evolving.

AREAS COVERED

This review will provide an overview of immune checkpoint inhibitor mechanism of action and how it relates to myocarditis pathophysiology, diagnostic algorithms and potential pitfalls, and emerging treatment approaches published until May 2023. We will focus on the state of the field and potential new directions in research and patient care. We will also provide consensus-based diagnostic and therapeutic algorithms endorsed by major societies.

EXPERT OPINION

The field needs more evidence-based approaches to risk stratification so that therapy can be tailored toward less cardiotoxic alternatives in high-risk patients. For diagnostic and therapeutic approaches, data from animal models are unlikely to provide conclusive evidence given the complexity of the human immune system. We strongly invite practitioners in the field to contribute every case to the ongoing multicenter registries.

Detection of acute myocarditis by ECG-triggered PET imaging of somatostatin receptors compared to cardiac magnetic resonance: preliminary results

Somatostatin receptors are overexpressed by inflammatory cells but not by cardiac cells, under normal conditions. This study assesses the detection of acute myocarditis by the ECG-triggered digital-PET imaging of somatostatin receptors (68Ga-DOTATOC-PET), as compared to Cardiac Magnetic Resonance (CMR) imaging, which is the reference diagnostic method in this setting.

METHODS

Fourteen CMR-defined acute myocarditis patients had a first 15-minutes ECG-triggered 68Ga-DOTATOC PET recording, 4.4 ± 3.0 days from peak troponin, and 10 had a second 4.3 ± 0.3 months later. Myocardial/blood SUVmax ratio was analyzed relative to the normal upper limit of 2.18, which had been previously determined from oncology 68Ga-DOTATOC-PET recordings of patients with a similar age range as the myocarditis patients.

RESULTS

An increased myocardial 68Ga-DOTATOC uptake relative to blood activity was invariably observed during the acute phase. SUVmax ratio exceeded 2.18 in all patients during the acute phase but also in 3/10 patients at 4-months, at a time when there were no more signs of active inflammation on CMR. A residual myocardial 68Ga-DOTATOC uptake was still observed on all gated-PET cine loops at 4-months.

CONCLUSION

These preliminary results suggest that 68Ga-DOTATOC ECG-triggered digital-PET may be as sensitive as CMR at detecting myocarditis during the acute phase and more sensitive at later stages.

Positron Emission Tomography in Heart Failure: From Pathophysiology to Clinical Application

Imaging modalities are increasingly being used to evaluate the underlying pathophysiology of heart failure. Positron emission tomography (PET) is a non-invasive imaging technique that uses radioactive tracers to visualize and measure biological processes in vivo. PET imaging of the heart uses different radiopharmaceuticals to provide information on myocardial metabolism, perfusion, inflammation, fibrosis, and sympathetic nervous system activity, which are all important contributors to the development and progression of heart failure. This narrative review provides an overview of the use of PET imaging in heart failure, highlighting the different PET tracers and modalities, and discussing fields of present and future clinical application.

Expansion of Disease Specific Cardiac Macrophages in Immune Checkpoint Inhibitor Myocarditis

Background

Immune checkpoint inhibitors (ICIs), antibodies targeting PD-1/PD-L1 or CTLA4 have revolutionized cancer management but are associated with devastating immune-related adverse events (irAEs) including myocarditis. The main risk factor for ICI myocarditis is the use of combination PD-1 and CTLA4 inhibition. ICI-myocarditis is often fulminant and is pathologically characterized by myocardial infiltration of T lymphocytes and macrophages. While much has been learned regarding the role of T-cells in ICI-myocarditis, little is understood regarding the identity, transcriptional diversity, and functions of infiltrating macrophages.

Methods

We employed an established murine ICI myocarditis model ( Ctla4 +/- Pdcd1 -/- mice) to explore the cardiac immune landscape using single-cell RNA-sequencing, immunostaining, flow cytometry, in situ RNA hybridization and molecular imaging and antibody neutralization studies.

Results

We observed marked increases in CCR2 + monocyte-derived macrophages and CD8 + T-cells in this model. The macrophage compartment was heterogeneous and displayed marked enrichment in an inflammatory CCR2 + subpopulation highly expressing Cxcl9 , Cxcl10 , Gbp2b , and Fcgr4 that originated from CCR2 + monocytes. Importantly, a similar macrophage population expressing CXCL9 , CXCL10 , and CD16α (human homologue of mouse FcgR4) was found selectively expanded in patients with ICI myocarditis compared to other forms of heart failure and myocarditis. In silico prediction of cell-cell communication suggested interactions between T-cells and Cxcl9 + Cxcl10 + macrophages via IFN-γ and CXCR3 signaling pathways. Depleting CD8 + T-cells, macrophages, and blockade of IFN-γ signaling blunted the expansion of Cxcl9 + Cxcl10 + macrophages in the heart and attenuated myocarditis suggesting that this interaction was necessary for disease pathogenesis.

Conclusion

These data demonstrate that ICI-myocarditis is associated with the expansion of a specific population of IFN-γ induced inflammatory macrophages and suggest the possibility that IFN-γ blockade may be considered as a treatment option for this devastating condition.

Gallium-68 Labelled Radiopharmaceuticals for Imaging Inflammatory Disorders

Inflammation is an important component of several chronic and debilitating diseases that result in significant morbidity and mortality. This is best evidenced within the cardiovascular system where it may manifest as atherosclerosis or myocarditis, and at the extreme end of the spectrum as myocardial infarction, ventricular remodeling, or cardiac failure. Early non-invasive detection and monitoring of inflammation in these and other settings may better guide patient management with resultant improved outcomes. Key role players in inflammation pathophysiology include chemokines, macrophages, neutrophils, fibroblasts, integrins, and reactive oxygen species, amongst others. Examples of receptor expression and over-expression include somatostatin receptors, CXCR4-, folate-, mannose-, TSPO- receptors and secretion of various vascular adhesion molecules (such as VCAM and ICAM). Gallium-68-based PET offers imaging possibilities for nearly all the major pathophysiological role players in inflammation, with mounting recent interest in macrophage differentiation, various forms of receptor expression and secretion of chemokines and vascular adhesion molecules. The advantages in terms of logistics and costs of having generator-produced PET probes available is well known, and a ⁶⁸Ga-based tracer provides easily translatable theranostic possibilities to especially Lu-177. Some of the more versatile and better validated Ga-68-based inflammation probes include ⁶⁸Ga-DOTA-TATE/NOC/TOC, ⁶⁸Ga-NOTA-RGD, ⁶⁸Ga-CXCR4, ⁶⁸Ga-citrate and ⁶⁸Ga-FAPI.

Positron emission tomography molecular imaging to monitor anti-tumor systemic response for immune checkpoint inhibitor therapy

Immune checkpoint inhibitors (ICIs) achieve a milestone in cancer treatment. Despite the great success of ICI, ICI therapy still faces a big challenge due to heterogeneity of tumor, and therapeutic response is complicated by possible immune-related adverse events (irAEs). Therefore, it is critical to assess the systemic immune response elicited by ICI therapy to guide subsequent treatment regimens. Positron emission tomography (PET) molecular imaging is an optimal approach in cancer diagnosis, treatment effect evaluation, follow-up, and prognosis prediction. PET imaging can monitor metabolic changes of immunocytes and specifically identify immuno-biomarkers to reflect systemic immune responses. Here, we briefly review the application of PET molecular imaging to date of systemic immune responses following ICI therapy and the associated rationale.

Imaging assessment of toxicity related to immune checkpoint inhibitors

In recent years, a wide range of cancer immunotherapies have been developed and have become increasingly important in cancer treatment across multiple oncologic diseases. In particular, immune checkpoint inhibitors (ICIs) offer promising options to improve patient outcomes. However, a major limitation of these treatments consists in the development of immune-related adverse events (irAEs) occurring in potentially any organ system and affecting up to 76% of the patients. The most frequent toxicities involve the skin, gastrointestinal tract, and endocrine system. Although mostly manageable, potentially life-threatening events, particularly due to neuro-, cardiac, and pulmonary toxicity, occur in up to 30% and 55% of the patients treated with ICI-monotherapy or -combination therapy, respectively. Imaging, in particular computed tomography (CT), magnetic resonance imaging (MRI), and 2-deoxy-2-[¹⁸F]fluoro-D-glucose positron emission tomography/computed tomography (¹⁸F-FDG-PET/CT), plays an important role in the detection and characterization of these irAEs. In some patients, irAEs can even be detected on imaging before the onset of clinical symptoms. In this context, it is particularly important to distinguish irAEs from true disease progression and specific immunotherapy related response patterns, such as pseudoprogression. In addition, there are irAEs which might be easily confused with other pathologies such as infection or metastasis. However, many imaging findings, such as in immune-related pneumonitis, are nonspecific. Thus, accurate diagnosis may be delayed underling the importance for adequate imaging features characterization in the appropriate clinical setting in order to provide timely and efficient patient management. ¹⁸F-FDG-PET/CT and radiomics have demonstrated to reliably detect these toxicities and potentially have predictive value for identifying patients at risk of developing irAEs. The purpose of this article is to provide a review of the main immunotherapy-related toxicities and discuss their characteristics on imaging.

Novel Radiotracers for Molecular Imaging of Myocardial Inflammation: an Update Focused on Clinical Translation of Non-18F-FDG Radiotracers

Purpose of Review

The purpose of this paper is to provide a focused update on recent advances in non-18F-FDG radiotracers for myocardial inflammatory diseases, with a focus on cardiac sarcoidosis and myocarditis.

Recent Findings

Novel radiotracers targeting molecular features of inflammation have the potential to visualize underlying molecular mechanisms key to the pathogenesis of inflammatory cardiomyopathies such as sarcoidosis and myocarditis. These radiotracers may provide unique opportunities for improved mechanistic insight, higher specificity, and better quantification of disease activity, as well as potential for guidance and monitoring of immunomodulatory therapies.

Summary

Novel radiotracers provide unique possibilities in diagnosis, prognostic performance, and therapy guidance for cardiac sarcoidosis and myocarditis.

Immunopathogenesis of Immune Checkpoint Inhibitor Induced Myocarditis: Insights from Experimental Models and Treatment Implications

Despite the extraordinary success of immune checkpoint inhibitors (ICIs) in cancer treatment, their use is associated with a high incidence of immune-related adverse events (IRAEs), resulting from therapy-related autoimmunity against various target organs. ICI-induced myocarditis is one of the most severe forms of IRAE, which is associated with risk of hemodynamic compromise and mortality. Despite increasing recognition and prompt treatment by clinicians, there remain significant gaps in knowledge regarding the pathophysiology, diagnosis and treatment of ICI-induced myocarditis. As the newly emerged disease entity is relatively rare, it is challenging for researchers to perform studies involving patients at scale. Alternatively, mouse models have been developed to facilitate research understanding of the pathogenesis of ICI-induced myocarditis and drug discovery. Transgenic mice with immune checkpoint genes knocked out allow induction of myocarditis in a highly reproducible manner. On the other hand, it has not been possible to induce ICI-induced myocarditis in wild type mice by injecting ICIs monotherapy alone. Additional interventions such as combinational ICI, tumor inoculation, cardiac sarcomere immunization, or cardiac irradiation are necessary to mimic the underlying pathophysiology in human cancer patients and to induce ICI-induced myocarditis successfully. This review focuses on the immunopathogenesis of ICI-induced myocarditis, drawing insights from human studies and animal models, and discusses the potential implications for treatment.

The spectrum of cardiovascular complications related to immune-checkpoint inhibitor treatment : Including myocarditis and the new entity of non inflammatory left ventricular dysfunction

BACKGROUND

The full range of cardiovascular complications related to the use of Immune checkpoint inhibitors (ICI) is not fully understood. We aim to describe the spectrum of cardiovascular adverse events (cvAEs) by presenting our real-world experience of the diagnosis and management of these complications.

METHODS

Two thousand six hundred and forty-seven (2647) patients were started on ICI treatment between 2014 and 2020. Data from 110 patients referred to the cardio-oncology service with a suspected cvAE was collected prospectively and analysed.

RESULTS

Eighty-nine patients (3.4%) were confirmed to have cvAEs while on ICI therapy. Myocarditis was the most frequent event (33/89), followed by tachyarrhythmia (27/89), non-inflammatory left ventricular dysfunction (NILVD) (15/89) and pericarditis (7/89). Results from myocarditis and non-inflammatory left ventricular dysfunction cohorts were compared. Myocarditis and NILVD showed significant differences in respect toof troponin elevation, cardiac magnetic resonance abnormalities and ventricular function. Dual ICI therapy and other immune related adverse events were more frequently associated with myocarditis than NILVD. There was a significant difference in the median time from starting ICI treatment to presentation with myocarditis versus NILVD (12 vs 26 weeks p = 0.049). Through early recognition of myocarditis, prompt treatment with steroids and interruption of ICI, there were no cardiovascular in-hospital deaths. NILVD did not require steroid treatment and ICI could be restarted safely.

CONCLUSIONS

The full spectrum of cardiovascular complications in patients with immune checkpoint inhibitors is much broader than initially described. Myocarditis remains the most frequent cvAE related to ICI treatment. A novel type of myocardial injury was observed and defined as Atrial tachyarrhythmias and NILVD were also frequent in this cohort. NILVD has a This differs fromdifferent presentation from ICI-related myocarditis, mainly usually presenting afterby the lack of inflammatory features on CMR and biomarkers and a later presentation in time.

Cardiovascular complications of immune checkpoint inhibitors for cancer

Over the last decade or so, there has been a paradigm shift in the oncologic care of patients with a range of solid tumour and haematologic malignancies, away from traditional cytotoxic chemotherapy and towards personalized cancer treatments, using both targeted therapy and immunotherapy. This shift has contributed to the remarkable and sustained increase in the number of cancer survivors and the longevity of patients with a cancer diagnosis. This review will focus on the cardiovascular effects of immune checkpoint inhibitors and will present a background on immune checkpoint inhibition for cancer, the epidemiology, potential mechanisms, the potential insights into cardiovascular biology, and a diagnostic and therapeutic approach to potential cases. Our understanding of the cardiovascular effects of immune checkpoint inhibitors needs to improve. However, the evolution necessarily needs to be rapid. Initial observations noted that immune checkpoint inhibitor therapy can lead to a fulminant myocarditis. Recent reports have expanded the effect of immune checkpoint inhibitor therapy on the cardiovascular system to include an increase in cardiac dysfunction without myocarditis, arrhythmias, venous thromboembolic disease, accelerated atherosclerosis, and atherosclerosis-related cardiovascular events. The association between immune checkpoint inhibitor therapy and an increase in these cardiovascular events is not only limited to events occurring within the first few weeks after starting therapy but can also include events that occur months to years after therapy. The latter observation is especially of relevance in those treated with adjuvant or neoadjuvant therapy. There needs to be a shift from recognition of an increase in cardiovascular events to currently approved immune checkpoint inhibitor therapies to understanding the mechanisms that lead to adverse cardiovascular effects, understanding who is at risk, and understanding what we can do about it.

Case report of elevation of high-sensitivity cardiac troponin T in the absence of cardiac involvement in immune checkpoint inhibitor-associated myositis

Background

Immune checkpoint inhibitors (ICIs) have markedly improved outcome in various types of cancer. ICI-associated myocarditis is one of the most severe immune-related adverse events. In particular, high concentrations of cardiac troponin T (cTnT) are associated with a high risk of death and early detection and vigorous therapy with high-dose steroids may improve survival. However, chronic skeletal muscle disorders have been suggested as a non-cardiac source of elevated high-sensitivity cardiac troponin T (hs-cTnT) concentrations.

Case summary

Here, we present the case of a 72-year-old patient with metastatic melanoma treated with nivolumab and ipilimumab, who developed symptomatic myositis [creatine kinase (CK) max. 3113 U/L]. Due to substantially elevated concentrations of hs-cTnT (max. 1128 ng/L, normal <14 ng/L, Elecsys), the patient was referred to the cardio-oncology unit for evaluation of concomitant myocarditis. The patient did not report any cardiac symptoms and there were no clinical signs of congestion or rhythm abnormalities. Concentrations of NT-proBNP were within the normal range. Echocardiography showed normal cardiac dimensions and normal systolic and diastolic function. Cardiac magnetic resonance imaging confirmed these findings and also showed no evidence of acute or post-inflammatory myocardial tissue changes. Absence of relevant cardiomyocyte injury was supported by determination of normal levels of cardiac troponin I concentrations and made endomyocardial biopsy in this severely ill patient unnecessary.

Discussion

Our observation documents ICI-induced myositis as an alternative non-cardiac cause of hs-cTnT elevation. A global cardiologic approach employing clinical and cardiac magnetic resonance imaging data as well as NT-proBNP and cardiac troponin I helps to identify false positive hs-TnT elevation under ICI therapy.

Cardiac imaging techniques for the assessment of immune checkpoint inhibitor-induced cardiotoxicity and their potential clinical applications

Immune checkpoint inhibitors (ICIs) have encouraged a paradigm shift in the clinical management of patients with cancer. Despite the dramatically improved tumor response and patient prognosis, ICIs have been associated with ICI-related myocarditis, which has a high fatality rate. Cardiac imaging plays a critical role in the assessment of cardiac injury. Echocardiography, cardiac magnetic resonance imaging, and targeted tracer-based cardiac molecular imaging techniques alone or in combination reflect pathophysiology and depict different aspects of lesions at different clinical stages, i.e., they have potentially complementary value. Imaging techniques for identifying ICI-induced cardiotoxicity at the early stage may reduce the incidence of adverse cardiovascular events. Particularly in planned ICI therapy among patients with cancer, improved monitoring approaches to identify patients who are at the highest risk of ICI-related myocarditis may help in refining clinical decisions, allowing treatment to be more accurately targeted toward patients who are most likely to benefit. In this study, we systematically reviewed the studies on cardiac imaging techniques for assessing ICI-induced cardiotoxicity. We elaborated about the potential applications of cardiac imaging techniques for the optimized management of patients with ICI-related myocarditis, including risk stratification, diagnosis, and prognosis.

Shining Damaged Hearts: Immunotherapy-Related Cardiotoxicity in the Spotlight of Nuclear Cardiology

The emerging use of immunotherapies in cancer treatment increases the risk of immunotherapy-related cardiotoxicity. In contrast to conventional chemotherapy, these novel therapies have expanded the forms and presentations of cardiovascular damage to a broad spectrum from asymptomatic changes to fulminant short- and long-term complications in terms of cardiomyopathy, arrythmia, and vascular disease. In cancer patients and, particularly, cancer patients undergoing (immune-)therapy, cardio-oncological monitoring is a complex interplay between pretherapeutic risk assessment, identification of impending cardiotoxicity, and post-therapeutic surveillance. For these purposes, the cardio-oncologist can revert to a broad spectrum of nuclear cardiological diagnostic workup. The most promising commonly used nuclear medicine imaging techniques in relation to immunotherapy will be discussed in this review article with a special focus on the continuous development of highly specific molecular markers and steadily improving methods of image generation. The review closes with an outlook on possible new developments of molecular imaging and advanced image evaluation techniques in this exciting and increasingly growing field of immunotherapy-related cardiotoxicity.