Durvalumab-Induced Myocarditis and Dilated Cardiomyopathy in a Patient With Non-small Cell Lung Cancer: A Diagnostic Conundrum

Immune checkpoint inhibitors have been a therapeutic oncological breakthrough in managing diverse malignancies. We present a 78-year-old male with stage IIIb non-small cell lung cancer (NSCLC) managed by concurrent chemotherapy with carboplatin/pemetrexed and radiotherapy followed by monthly durvalumab injections. He presented to the hospital with shortness of breath and fluid overload after eight months of starting durvalumab. Workup, including laboratory investigations, coronary angiography, and stress myocardial magnetic resonance imaging, increased our suspicion for the diagnosis of durvalumab-induced myocarditis and nonischemic dilated cardiomyopathy. He was managed with aggressive diuresis and pulse dose steroids with an improvement in his symptoms and his cardiac function. This case illustrates an under-reported clinical side effect in the era of advancement in oncological immunotherapy.