[Trastuzumab Deruxtecan for EGFR-mutant Lung Adenocarcinoma
with Acquired High-level HER2 Amplification: A Case Report].

Trastuzumab deruxtecan is a newly developed antibody-drug conjugate (ADC) designed to overcome human epidermal growth factor receptor 2 (HER2) aberrations. Studies have confirmed that Trastuzumab deruxtecan yields promising efficacy with a manageable safety profile in previously treated non-small cell lung cancer (NSCLC) patients harboring HER2 mutations. However, data on efficacy of Trastuzumab deruxtecan for acquired HER2-amplified NSCLC are limited. Here, we report a case of a patient with metastatic lung adenocarcinoma who developed acquired high-level HER2 amplification (20 copies) after 2nd-line Osimertinib. A partial response (PR) was achieved with reduced-dose Trastuzumab deruxtecan. Plasma next-generation sequencing (NGS) further confirmed successful inhibition of HER2 amplification. 
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