Abstract
Immunotherapy is an important part of the first-line treatment for lung squamous cell carcinoma (LUSC) in the current guidelines. However, in case when patients experience immunotherapy-related adverse reactions, immunotherapy may be discontinued. Antibody-drug conjugates (ADCs) may be an alternative treatment if the patient harbors actionable mutations. Herein, we present a case of brain metastatic LUSC harboring HER2 mutation who experienced hypophysitis after immunotherapy. This patient benefited from Trastuzumab Deruxtecan (T-DXd) after discontinuing immunotherapy. Therefore, T-DXd may be an alternative treatment option for LUSC patients with HER2 mutation who are unable to continue immunotherapy.