(1171) Chemotherapy (Trastuzumab)-Induced Pneumonitis: A Case Report

Introduction: Trastuzumab, a monoclonal antibody targeting HER2 protein, is crucial in the treatment of HER2-positive breast cancer. This therapy has significantly improved prognosis and survival. Pulmonary complications such as interstitial lung disease (ILD) and pneumonitis have been reported with onset varying from brief to extended treatment periods. We describe a case of progressive dyspnea in a patient receiving long-term trastuzumab.

Description: A 58-year-old female with HER2-positive metastatic breast cancer post right modified mastectomy and radiotherapy with a three-week history of shortness of breath, productive cough, and exertional dyspnea. She denied hemoptysis, night sweats, and sick contacts. She was hypoxic with oxygen saturation of 88%. She had been on trastuzumab and anastrozole for four years. A chest X-ray revealed patchy infiltrates in the right lung apex and lower lobe. She received antibiotics without improvement. Computed tomography (CT) scan of the chest revealed diffuse ground-glass opacities, suggesting pneumonitis. Infectious etiologies, pulmonary embolism, and heart failure were ruled out through appropriate tests. Given the temporal relationship with trastuzumab therapy and a negative workup, trastuzumab-induced subacute pneumonitis was considered. She was started on intravenous methylprednisolone and discharged on oral prednisone and 2 L of oxygen via nasal cannula due to persistent hypoxia. At a follow-up appointment, pulmonary function tests (PFTs) indicated restrictive disease with increased residual volume to total lung capacity (RV/TLC) ratio and decreased diffusing capacity for carbon monoxide (DLCO) consistent with ILD.

Discussion: Trastuzumab can lead to pulmonary toxicity, even years after therapy. Trastuzumab-induced pneumonitis, though rare, should be considered in patients with unexplained respiratory symptoms and a history of trastuzumab use. CT scan plays a crucial role in early detection, often revealing diffuse ground-glass opacities and consolidations. Corticosteroids are the mainstay of treatment for drug-induced pneumonitis. Oxygen therapy, bronchodilators, and supportive measures may be required depending on the severity of the respiratory symptoms.