Research suggests that quantitative her2 profiling may help refine the use of trastuzumab deruxtecan in treating metastatic breast cancer. Studies indicate that her2 tissue and plasma profiling, as well as genomic assays, can predict the effectiveness of trastuzumab deruxtecan. However, there are also reports of existing evidence gaps and challenges related to her2 expression in breast cancer, highlighting the need for further assessment and improvement.