This aligns with several previous studies that have shown an association of PI3KCA mutations with a lower pCR rate in patients with HER2-positive breast cancer who received neoadjuvant trastuzumab.37–40 Another noteworthy finding from our biomarker analysis is that the combination of TMB levels and mutational status in the RTK-RAS pathway may assist to identify patients who may benefit from the response-guided strategy. Here, ERBB2 is linked to breast cancer.