To evaluate the efficacy and safety of T-DXd in the treatment of HER2-positive breast cancer with brain metastases after treatment with 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

Patients with brain metastases from HER2 positive breast cancer after treatment with pyrotinib