Thymus alterations and susceptibility to immune checkpoint inhibitor myocarditis.

Immune checkpoint inhibitors (ICI) have transformed the therapeutic landscape in oncology. However, ICI can induce uncommon life-threatening autoimmune T-cell-mediated myotoxicities, including myocarditis and myositis. The thymus plays a critical role in T cell maturation. Here we demonstrate that thymic alterations are associated with increased incidence and severity of ICI myotoxicities. First, using the international pharmacovigilance database VigiBase, the Assistance Publique Hôpitaux de Paris-Sorbonne University data warehouse (Paris, France) and a meta-analysis of clinical trials, we show that ICI treatment of thymic epithelial tumors (TET, and particularly thymoma) was more frequently associated with ICI myotoxicities than other ICI-treated cancers. Second, in an international ICI myocarditis registry, we established that myocarditis occurred earlier after ICI initiation in patients with TET (including active or prior history of TET) compared to other cancers and was more severe in terms of life-threatening arrythmias and concurrent myositis, leading to respiratory muscle failure and death. Lastly, we show that presence of anti-acetylcholine-receptor antibodies (a biological proxy of thymic-associated autoimmunity) was more prevalent in patients with ICI myocarditis than in ICI-treated control patients. Altogether, our results highlight that thymic alterations are associated with incidence and seriousness of ICI myotoxicities. Clinico-radio-biological workup evaluating the thymus may help in predicting ICI myotoxicities

Immune Checkpoint Inhibitor Myocarditis and Left Ventricular Systolic Dysfunction.

Immune checkpoint inhibitors (ICIs) have transformed cancer treatment, but ICI myocarditis (ICI-M) remains a potentially fatal complication. The clinical implications and predictors of left ventricular ejection fraction (LVEF) <50% in ICI-M are not well understood. The aim of this study was to identify factors associated with LVEF <50% vs ≥50% at the time of hospitalization for ICI-M. A secondary objective was to evaluate the relationship between LVEF and 30-day all-cause mortality. The International ICI-Myocarditis Registry, a retrospective, international, multicenter database, included 757 patients hospitalized with ICI-M. Patients were stratified by LVEF as reduced LVEF (<50%) or preserved LVEF (≥50%) on admission. Cox proportional hazards models were used to assess the associations between LVEF and clinical events, and multivariable logistic regression was conducted to examine factors linked to LVEF. Of 757 patients, 707 had documented LVEFs on admission: 244 (35%) with LVEF <50% and 463 (65%) with LVEF ≥50%. Compared with patients with LVEF ≥50%, those with LVEF <50% were younger (<70 years), had a body mass index of <25 kg/m <sup>2</sup> , and were more likely to have received chest radiation (24.2% vs 13.5%; P < 0.001). Multivariable analysis identified predictors of LVEF <50%, including exposure to v-raf murine sarcoma viral oncogene homolog B1/mitogen-activated protein kinase inhibitors, pre-existing heart failure, dyspnea at presentation, and at least 40 days from ICI initiation to ICI-M onset. Conversely, myositis symptoms were associated with LVEF ≥50%. LVEF <50% was marginally associated with 30-day all-cause mortality (unadjusted log-rank P = 0.062; adjusted for age, cancer types, and ICI therapy, HR: 1.50; 95% CI: 1.02-2.20). Dyspnea, time from ICI initiation, a history of heart failure, and prior cardiotoxic therapy may be predictors of an initial LVEF <50% in patients with ICI-M

Immune checkpoint inhibitor-associated myocarditis: a novel risk score.

Immune checkpoint inhibitors (ICI) are associated with life-threatening myocarditis but milder presentations are increasingly recognized. The same autoimmune process that causes ICI myocarditis can manifest concurrent generalized myositis, myasthenia-like syndrome, and respiratory muscle failure. Prognostic factors for this 'cardiomyotoxicity' are lacking. The main aim of this study was to determine predictors and construct a risk score associated with negative outcomes in patients admitted for ICI myocarditis. A multicentre registry collected data retrospectively from 17 countries between 2014 and 2023. A multivariable Cox regression model was used to determine risk factors for the primary composite outcome: time to severe arrhythmia, heart failure, respiratory muscle failure, and/or cardiomyotoxicity-related death. Covariates included demographics, comorbidities, cardiomuscular symptoms, diagnostics, and treatments. Time-dependent covariates were used, and missing data were imputed. A point-based prognostic risk score was derived and externally validated. In 748 patients (67% male, age 23-94 years), 30-day incidence of the primary composite outcome, cardiomyotoxic death, and overall death were 33%, 13%, and 17%, respectively. By multivariable analysis, the primary composite outcome was associated with active thymoma (hazard ratio [HR] 3.6, 95% confidence interval [CI] 1.7-7.7), presence of cardiomuscular symptoms (HR 2.6 [1.5-4.2]), low QRS voltage on presenting electrocardiogram (HR for ≤0.5 mV vs >1 mV 1.9 [1.1-3.1]), left ventricular ejection fraction (LVEF) < 50% (HR 1.7 [1.1-2.6]), and incremental troponin elevation (HR 1.8 [1.4-2.4], 2.9 [1.8-4.7], and 4.6 [2.3-9.3], for 20, 200, and 2000-fold above upper reference limit, respectively). A prognostic risk score developed using these parameters showed good performance; 30-day primary outcome incidence increased gradually from 4% (risk score = 0) to 81% (risk score ≥ 4). This risk score was externally validated in two independent French and US cohorts. This risk score was used prospectively in the external French cohort to identify low-risk patients who were managed with no immunosuppression resulting in no cardiomyotoxic events. ICI-associated myocarditis can manifest with high morbidity and mortality. Myocarditis severity is associated with magnitude of troponin, thymoma, low QRS voltage, depressed LVEF, and cardiomuscular symptoms. A risk score incorporating these features performed well. NCT04294771 and NCT05454527