Pembrolizumab: Grade 3 immune-related myositis.

A 67-year-old man developed immune-related myositis while being treated with pembrolizumab for non-small cell lung cancer. He had a history of smoking and was diagnosed with locally advanced pulmonary sarcomatoid carcinoma. After receiving three cycles of chemotherapy and immunotherapy, his tumor size and lymph nodes significantly reduced. However, he developed grade 3 immune-related myositis after one cycle of adjuvant pembrolizumab therapy. The treatment was discontinued, and the patient experienced muscle weakness but eventually made a full recovery without specific treatment. He is currently in excellent health with no signs of recurrence. [Extracted from the article]