Interestingly, when focusing on the ERBB2 copy numbers in the paired samples, we observed a trend of decreasing ERBB2 copy numbers in post-T-DXd samples compared to pre-T-DXd samples; however, cautions should be taken for this trend might have stemmed from the technical limitations of targeted sequencing or the discrepancy in tumor purity in each sample. This evidence concerns the gene ERBB2 and neoplasm.