A41-17 A Case of Afatinib-associated Pneumonitis in a Patient With Egfr-mutant Non-small Cell Lung Cancer

Abstract Introduction Afatinib is a second-generation epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor (TKI) that has demonstrated clinical efficacy in patients with non-small cell lung cancer (NSCLC) harboring EGFR mutations. Typical adverse events related to Afatinib are rash or gastrointestinal disturbances; a less common but significantly serious effect is drug-induced pneumonitis. We present a case of a patient with recently diagnosed metastatic lung adenocarcinoma, who, after initiating treatment with afatinib, develops worsening dyspnea and hypoxemia. Case presentation A 67-year-old female with recently diagnosed stage IV EGFR-mutant lung adenocarcinoma presented to the emergency department due to progressive shortness of breath and hypoxemia. One month prior, given her uncommon EGFR mutation, she had been started on Afatinib in the outpatient setting. The patient was hypoxic on room air, requiring oxygen supplementation with high-flow nasal cannula. Laboratory studies revealed a normal leukocyte count, chest radiograph showed diffuse bilateral interstitial infiltrates. CT pulmonary angiography ruled out pulmonary embolism but demonstrated confluent ground-glass opacities throughout both lungs, which had increased compared to prior outpatient imaging. No significant pleural effusion. A respiratory viral panel, MRSA nasal swab, Legionella and Streptococcus pneumoniae urine antigens, serum galactomannan, and β-D-glucan were negative. Due to concerns about her immunocompromised state, empirical antibiotics were started. The patient was admitted for acute hypoxic respiratory failure. Differential diagnosis included community-acquired pneumonia, atypical infections, cancer progression, and Afatinib-induced pneumonitis. Due to high concern of pneumonitis, Afatinib was held, and methylprednisolone at 1.5mg/kg was initiated. Antibiotics were given for a total of 5 days. The patient improved steadily, and she was titrated off supplemental oxygen. She was discharged on a 6-week tapering course of steroids with close outpatient follow-up. Afatinib was permanently discontinued. At a 3-week follow-up, she remained clinically stable, with repeat CT imaging showing improvement in bilateral infiltrates. Discussion EGFR TKI-induced pneumonitis is a less common but potentially fatal adverse complication. Its diagnosis is challenging due to nonspecific clinical and radiologic findings that may mimic infection or tumor progression. Management involves discontinuation of the offending agent and initiation of corticosteroids. However, case reports and small series have described a wide range of steroid regimens, varying from moderate to high doses, with treatment courses lasting from days to weeks. Outcomes have also been variable, further complicating therapeutic decisions. This case shows the importance of prompt identification and early treatment; however, further studies are required to determine ideal dosing strategies. This abstract is funded by: None