Abstract Introduction Malignant pericardial effusion is a rare initial manifestation of lung adenocarcinoma and isassociated with poor prognosis. Epidermal growth factor receptor (EGFR) tyrosine kinaseinhibitors (TKIs) have transformed outcomes in molecularly selected non-small cell lung cancer(NSCLC), yet their impact in patients who initially present with life-threatening complications isless frequently described. We report a case of EGFR-mutated metastatic lung adenocarcinomawith diffuse bilateral pulmonary metastases and malignant pericardial tamponade demonstratingdramatic radiologic response to osimertinib therapy. Case Presentation A 68-year-old never-smoking woman with a past medical history of hypothyroidism and asthmapresented with progressive dyspnea, orthopnea, and pleuritic chest discomfort. She wastachycardic but saturating 100 % on 2 L/min nasal cannula. Physical examination revealeddistant heart sounds and decreased breath sounds bilaterally. Laboratory testing wasunremarkable. CT chest demonstrated numerous bilateral pulmonary nodules measuring up to1.2 cm with associated interlobular septal thickening, mediastinal and right axillarylymphadenopathy, and a small circumferential pericardial effusion. Transthoracicechocardiography confirmed early tamponade physiology. Emergent pericardiocentesis wasperformed that drained 400 mL of hemorrhagic fluid. Cytology revealed adenocarcinomaconsistent with lung origin (TTF-1 and Napsin A positive). While awaiting molecular results, shebegan empiric carboplatin and pemetrexed chemotherapy. Upon confirmation of EGFRmutation, systemic therapy was transitioned to osimertinib 80 mg daily. A follow-up CT chestapproximately three months later demonstrated significant interval reduction in the size andnumber of bilateral pulmonary nodules, consistent with a strong treatment response. There wasno recurrence of pericardial effusion, and the patient reported marked improvement in dyspneaand functional capacity on continued osimertinib therapy. Discussion This case underscores the importance of early genomic testing in suspected lungadenocarcinoma. Osimertinib, a third-generation EGFR-TKI, is highly effective in tumorsharboring sensitizing EGFR mutations and may induce rapid regression of metastatic burden.This case illustrates a robust treatment response despite initial disseminated disease andhemodynamic compromise.ConclusionOsimertinib can achieve rapid and meaningful disease regression in EGFR-mutated NSCLC,even when patients initially present with malignant pericardial tamponade and extensive pulmonary metastases. Early molecular diagnosis enables timely initiation of precision therapyand may dramatically alter disease trajectory. This abstract is funded by: none
Sonti et al. (Fri,) studied this question.