A41-20 Cetuximab-Induced Pneumonitis in a Patient With Metastatic Cutaneous Squamous Cell Carcinoma: A Rare and Fatal Complication

Abstract Introduction Cetuximab, a chimeric monoclonal antibody directed against the epidermal growth factor receptor (EGFR), is commonly employed in the treatment of metastatic colorectal cancer and head and neck squamous cell carcinoma (HNSCC) 1. Although generally well tolerated, cetuximab therapy can lead to a spectrum of adverse effects, including rare but potentially fatal pulmonary toxicities such as drug-induced pneumonitis or interstitial lung disease (ILD). The reported incidence of cetuximab-associated ILD is approximately 4.5% 2, with mortality rates exceeding 40% in severe cases 3. We describe a fatal case of cetuximab-induced pneumonitis in a patient with metastatic cutaneous squamous cell carcinoma (SCC), underscoring the diagnostic challenges and the critical importance of early recognition and intervention. Case Presentation A 75-year-old man with diabetes, coronary artery disease, and chronic kidney disease presented with progressive fatigue and hypoxemia two weeks after initiating concurrent radiation and cetuximab for stage IV metastatic cutaneous SCC. Chest radiography revealed dense bilateral interstitial opacities concerning for pneumonia with preserved cardiac function on echocardiogram. Despite broad-spectrum antibiotics and diuretics, his respiratory status deteriorated. Infectious studies, including respiratory viral and atypical pathogen panels, were negative. Given worsening bilateral infiltrates, absence of infection, and temporal association with cetuximab initiation, drug-induced pneumonitis was strongly suspected. High-dose intravenous methylprednisolone was started with stabilization is his symptoms. However, the patient elected to transition to comfort care, ultimately passed away. Discussion Cetuximab-induced pneumonitis is an uncommon but potentially fatal complication, often confounded by infectious or radiation-induced causes. The proposed mechanism involves immune-mediated alveolar injury secondary to EGFR blockade 2. Symptoms typically appear within 23 days of treatment initiation 2. Risk factors include advanced age, prior interstitial lung disease, poor performance status, and concurrent radiotherapy 4. Smoking and elevated serum KL-6 levels have also been linked to increased susceptibility 2. Early-onset pneumonitis is associated with higher mortality 3. Prompt discontinuation of cetuximab, exclusion of infection, and initiation of corticosteroid therapy are crucial for improving outcomes 3,4. This case underscores the importance of early recognition of new respiratory symptoms in patients receiving cetuximab, particularly during combined chemoradiation. Conclusion Although rare, cetuximab-induced pneumonitis carries high morbidity and mortality. Clinicians should maintain a high index of suspicion for this diagnosis and initiate prompt management to improve prognosis.Fig.1 Portable chest radiograph showing diffuse bilateral interstitial and alveolar infiltrates, more prominent in the right lung, consistent with acute pneumonitis in the setting of recent cetuximab therapy. This abstract is funded by: None