Abstract Introduction Pembrolizumab is a drug that is part of a class of immunotherapy drugs that targets Programmed Cell Death Protein 1 (PD-1) preventing immune cells from attacking the body’s own tissues. Granulomatous pneumonitis is a rare immune-related adverse event (irAE) associated with immune checkpoint inhibitor (ICI) treatment and typically affects bilateral lungs; making unilateral lung involvement rare. Sarcoid-like granulomatosis is characterized by non-caseating granulomas without typical multisystem involvement and has been increasingly observed in patients undergoing chemotherapy. Case The patient is a 61-year-old male with pertinent past medical history of tobacco dependency and stage IV non-small-cell lung carcinoma status post chemotherapy and radiation complicated by brain metastasis status post cyberknife who was referred to Pulmonology for evaluation of a right lower lobe lung mass. The patient completed chemotherapy with carboplatin, pemetrexed, and pembrolizumab due to recurrent frontal lobe lesions with associated mediastinal adenopathy. PET CT obtained after chemotherapy showed a hypermetabolic large right lower lobe lung mass. Associated symptoms included dyspnea, cough, and unintentional weight loss of 20-30 pounds. The patient underwent navigational bronchoscopy and endobronchial ultrasound, and pathology showed granulomatous pneumonitis with no malignant cells seen; staining positive for CD3, CD20, and CD68. Treatment of pembrolizumab-induced granulomatous sarcoid-like reaction included prednisone taper of 30mg daily for two weeks, then 20mg daily for two weeks, then 10mg daily for two weeks, and then 5mg daily for two weeks; and levofloxacin 750mg daily for 7 days. Repeat CT imaging 2 months after treatment showed resolution of initial granulomatous pneumonitis findings and only residual scarring in the right lower lobe. Oncology terminated the patient’s pembrolizumab treatment. Discussion Sarcoid-like reactions (SLR) typically affect the lungs and skin. There is no associated dose in which SLRs develop, and treatment with corticosteroids is not always required. Commencement of treatment typically occurs with persistent symptoms of dyspnea, fever, cough, and fatigue. Based on previous studies, SLR trends toward increased length of time to cancer progression or recurrence and overall improved mortality. The mechanisms in which these granulomas form has not been studied extensively; however, the literature states ICIs can potentiate cell lines associated with granuloma formation. Neoadjuvant ICI therapy is now being initiated prior to surgical intervention more than before and with lymph node sampling during surgical resections, this can lead to increased diagnoses of SLR. Further investigation into the mechanism and pathophysiology of SLRs is needed to provide more information on this disease process. This abstract is funded by: None
Duong et al. (Fri,) studied this question.