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This case highlights an unusual presentation of pneumonitis after immune checkpoint inhibitor therapy in a patient with small cell lung cancer.

May 20, 2026

B80-6-30 Atypical Presentation of Immune Checkpoint Inhibitor-Induced Pneumonitis in a Patient With Advanced Small Cell Lung Cancer

Puntos clave

This case highlights an unusual presentation of pneumonitis after immune checkpoint inhibitor therapy in a patient with small cell lung cancer.
Patient initiated on Durvalumab, Cisplatin, and Etoposide; received 4 cycles of chemotherapy followed by 12 cycles of Durvalumab.
Monitoring and imaging conducted to assess lung inflammation; intravenous methyl prednisone administered for treatment.
Diagnosis made by excluding other causes like infection or tumor progression, supported by symptom improvement after steroid treatment.
Initial chest X-ray showed mixed infiltrates concerning for pneumonia or pneumonitis.
Methyl prednisone treatment led to gradual symptom improvement, confirming the diagnosis of immune checkpoint inhibitor pneumonitis.
Diagnosis highlighted the need for awareness of atypical symptom presentations in immunotherapy patients.

Resumen

Abstract Introduction Immunotherapy drugs are monoclonal antibodies designed to prevent checkpoint proteins from binding to partner proteins, ultimately allowing for T cells to attack cancer cells. Pneumonitis is defined as focal or diffuse inflammation of the lung parenchyma due to damage from not only anti-programmed death 1 (PD-1)/programmed death ligand 1 (PD-L1) immune checkpoint inhibitors, but inhalation of sensitized allergens, chemicals, various antibiotics such as sulfonamides or even medications such as amiodarone. In this case, we present a patient diagnosed with small cell lung cancer, who later developed an unclear presentation of pneumonitis after initiation of durvalumab. Case A 59-year-old male with a history of metastatic head and neck squamous cell carcinoma in remission with newly diagnosed extensive stage small cell lung cancer in remission. He was initiated on Durvalumab 1,500 mg day 1, Cisplatin 75 mg/m2 day 1, Etoposide 100 mg/m2 days 1-3 for 4 cycles followed by Durvalumab for 12 cycles. He presented with fatigue, sudden weight loss, and treatment induced cachexia. He was afebrile without a cough or shortness of breath. Laboratory results revealed a normal white blood cell count with mild neutrophilia. Initial chest X-Ray showed development of mixed infiltrates throughout both lungs concerning for possible pneumonia versus immune checkpoint inhibitor induced pneumonitis. Intravenous methyl prednisone was initiated with gradual improvement in his symptoms. Based on a positive response from intravenous steroids, and review of imaging it was consistent with immune checkpoint inhibitor pneumonitis. Discussion This case demonstrates atypical presentation of pneumonitis in patients receiving checkpoint inhibitor treatment. Immune checkpoint inhibitor-induced pneumonitis (CIP) represents an immune-related adverse event characterized by pulmonary inflammation. It may originate from treatments involving anti-PD-1, anti-PD-L1, or anti-cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) antibody therapies, typically manifesting early during treatment. Diagnosis necessitates the exclusion of infection and tumor progression, frequently achieved through bronchoscopy with bronchoalveolar lavage (BAL) in cases of moderate to severe presentation. Mild cases can be addressed by withholding immune checkpoint inhibitors and close monitoring, whereas moderate to severe cases require systemic corticosteroids or immunosuppressive agents for resolution. Chronic pneumonitis can lead to pulmonary hypertension, lung fibrosis, irreversible lung damage, and death. This abstract is funded by: None

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