Myocarditis related to immune checkpoint inhibitors treatment: two case reports and literature review

Immune checkpoint inhibitors can cause immune-related toxicity in various systems, and myocarditis is the most serious life-threatening toxicity. This report introduces diagnosis and treatment of two cases which developed myocarditis after receiving PD-1 inhibitors therapy. The first case was a 77-year-old male with chordoma, who was treated by third-line sintilimab combined with anlotinib, and presented with symptoms of chest tightness, shortness of breath and upper eyelid ptosis three weeks later. He was diagnosed as immune-checkpoint-inhibitors-related myocarditis and myositis-myasthenia-gravis overlap syndrome based on his clinical symptoms, serum biomarkers, electrocardiogram, echocardiogram, and characteristic findings on cardiac 18F-FDG PET-MRI. Methylprednisolone was given 480 mg/d initially and was gradually reduced to 40 mg/d in 4 weeks, with the myocardial injury biomarkers declined in the same time. The second case was a 69-year-old female with advanced non-small cell lung cancer, who was treated by pemetrexed combined with bevacizumab and camrelizumab, and presented with palpitations 20 days later. She was diagnosed as immune-checkpoint-inhibitors-related myocarditis based on her clinical symptoms, serum biomarkers, electrocardiogram and echocardiogram. Methylprednisolone was given 240 mg/d initially and was gradually reduced to 40 mg/d with good response of myocardial injury biomarkers decline. However, the patient developed fatal myasthenia gravis afterwards, with little response to all treatments. These two cases revealed that, early detection and timely intervention, including discontinuation of immune checkpoint inhibitors and initiation of adequate steroid therapy, can reduce morbidity and mortality and improve prognosis.