• Age\> 18 years old, female

• KPS≥70

• HER2-positive breast cancer is confirmed by the pathology laboratory with an immunohistochemical (IHC) score of 3+ and/or 2+ and a positive in situ hybridization (ISH) test (ISH amplification rate ≥ 2.0)

• Brain metastasis confirmed by MRI, in line with the indications for whole brain radiotherapy

• At least one measurable brain lesion exists according to the RECIST 1.1 standard

• Unlimited number of previous chemotherapy lines

• Have not used capecitabine in the past, or progressed 6 months after capecitabine stopped, or progressed after capecitabine as adjuvant therapy stopped for one year

• The expected survival period is more than 12 weeks

• Patients must have adequate organ function, criteria as follows.

∙ Blood routine examination：Absolute Neutrophil Count (ANC)≥1.5×109/L；PLT ≥100×109/L； Hb ≥90g/L

‣ Blood chemistry test：TBIL ≤1.5 times the upper limit of normal (ULN); ALT and AST≤3 times ULN; For patients with liver metastases, ALT and AST≤5×ULN; BUN and Cr≤1×ULN and creatinine clearance ≥50mL/min (CockcroftGault formula);

‣ Ultrasonic cardiogram: LVEF≥50%

‣ 12-lead ECG: The QT interval (QTcF) corrected by Fridericia's method is \< 470 ms

⁃ Patients with known hormone receptor status

⁃ Patients need to voluntarily join this study after they fully understand and sign the informed consent form. Patients need to have good compliance and be willing to cooperate with follow-up.