Efficacy of T-Dxd in the Treatment of HER2-positive BCBM After Prior Pyrotinib

Inclusion Criteria: (1) Women ≥18 years of age :(2) pathological diagnosis of HER2-positive breast cancer, defined as positive immunohistochemistry detection (+++) or FISH(Fluorescent In Situ Hybridization); (3) Imaging evidence of brain metastases; (4) Progression of brain metastases after prior treatment with pyrotinib, defined as progression of new or pre-existing brain metastases during treatment with pyrotinib; (5)ECOG score ≤3 points; (6) The efficacy of T-DXd should be evaluated at least once after treatment; (7) Bone marrow and organ functions are basically normal; (8) Complete medical records Exclusion Criteria: * Has uncontrolled or significant cardiovascular disease * Has history of (noninfectious) interstitial lung disease (ILD)/pneumonitis that required steroids, has current ILD/pneumonitis, or suspected ILD/ pneumonitis that cannot be ruled out by imaging at screening * Has any medical history or condition that per protocol or in the opinion of the investigator is inappropriate for the study