1) Reassessment of hormone receptor and HER2 status when breast cancer metastasizes can provide important information to guide treatment, as discordance rates between primary and metastatic tumors have been found to be as high as 30-50% for hormone receptors and 10-15% for HER2 in some studies.
2) Early administration of anti-HER2 targeted therapy for HER2-positive breast cancer is important, as several studies have shown improved outcomes when trastuzumab is started concurrently or shortly after diagnosis of metastatic disease rather than at later stages.
3) Continuing HER2-targeted therapy beyond progression on initial regimens provides clinical benefit, as evidenced by trials showing improved outcomes with extended trast