Aromatase Inhibitor Therapy Increases the Risk of New-Onset Atrial Fibrillation in Patients With Breast Cancer.

Background: Previous studies suggest that aromatase inhibitors (AIs) increase the risk of adverse cardiovascular events and cardiac arrhythmias in patients with breast cancer, but it is unclear whether AIs also increase the risk of new-onset atrial fibrillation (AF). Objectives: The purpose of this study was to investigate whether the use of AIs was associated with an increased risk of new-onset AF in patients with breast cancer. Methods: We performed a retrospective analysis involving 5,707 patients with breast cancer (mean age 63.9 ± 11.2 years and 99.9% women) who received adjunctive hormone therapy with an AI (AI group, n = 4,878) or tamoxifen (tamoxifen group, n = 829) in Hong Kong between January 1, 1999, and December 31, 2020. After propensity score matching, there were 1,658 and 829 patients with balanced characteristics in the AI group and tamoxifen group, respectively. Results: After 8,863 patient-years of follow-up, patients who were prescribed AI had a trend toward more new-onset arrhythmias compared with those prescribed tamoxifen (0.62 vs 0.30 per 100 patient-years; crude HR: 2.05; P = 0.053). The difference in arrhythmic risk was mainly driven by a higher incidence rate of new-onset AF in the AI group (0.59 vs 0.27 per 100 patient-years; crude HR: 2.18; P = 0.046). The use of AIs was confirmed to be an independent risk factor for new-onset AF on multivariate analysis (adjusted HR: 2.75; P = 0.01). Conclusions: Among breast cancer patients prescribed adjunctive hormonal therapy, AI was associated with an increased risk of new-onset AF. Regular surveillance for new-onset AF should be considered in breast cancer patients treated with an AI.

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.