Supplementary Material for: Entrectinib-induced pericarditis with cardiac tamponade in a patient with neurotrophic tropomyosin receptor kinase 1 fusion-positive breast cancer

Introduction: Entrectinib is a multikinase inhibitor used to treat neurotrophic tropomyosin receptor kinase (NTRK) fusion-positive, locally advanced, or metastatic tumors. Cardiovascular events, such as congestive heart failure and myocarditis, have been reported in association with entrectinib use. Case Presentation: A 31-year-old female with NTRK1 fusion-positive breast cancer presented to our hospital with dyspnea and orthopnea 21 days after initiating entrectinib therapy (600 mg/day orally). Transthoracic echocardiography revealed circumferential pericardial effusion with diastolic right atrial and ventricular collapse. Consequently, she was diagnosed with pericarditis complicated by cardiac tamponade, and pericardiocentesis was performed. Cardiac tamponade resolved after discontinuation of entrectinib and initiation of corticosteroid therapy. Subsequently, larotrectinib (200 mg/day orally) was initiated. Conclusion: To our knowledge, this is the first reported case of entrectinib-induced pericarditis complicated by cardiac tamponade. Patients should be closely monitored for signs of pericarditis and cardiac tamponade at the start of entrectinib therapy. In patients who develop cardiovascular toxicity due to entrectinib, larotrectinib may be considered as an alternative treatment.