The HER2CLIMB study showed that adding tucatinib to trastuzumab and capecitabine significantly improved outcomes in HER2-positive breast cancer with BMs, reducing intracranial progression or death by 68% and doubling the intracranial objective response rate (47.3% vs. 20.0%), establishing its role as an effective treatment option [87]. This evidence concerns the gene ERBB2 and breast cancer.