• Stage IIa only: advanced or metastatic solid tumor confirmed by histopathology or cytology.

• Only stage IIb and III: Patients with mCRC confirmed by histopathology or cytology, who are not suitable for radical surgical excision or local therapy, and who have not previously received systemic antitumor therapy for CRC (including systemic chemotherapy, molecular targeted drug therapy, biotherapy and investigational therapy, and have completed adjuvant chemotherapy for ≥6 months) can be admitted to the group.

• Age range from 18 to 75 years old (including the critical value), gender is not limited.

• Proof of HER2-positive (IHC) 3+, or IHC 2+ and FISH +, by immunohistochemical (IHC) staining and/or fluorescence in situ hybridization (FISH), and wild type KRAS, NRAS, and BRAF genes. HER2 positive status was interpreted according to the current Chinese guidelines for detecting HER2 in gastric cancer.

• According to the researchers' judgment, CAPEOX scheme is suitable.

• At least one measurable lesion according to RECIST 1.1 criteria (tumor lesion located in the area of prior radiotherapy or other local regional treatment site is generally not considered as a measurable lesion unless it shows definite progression or persists three months after radiotherapy).

• The physical status score of the Eastern Oncology Consortium (ECOG) was 0-1.

• Expected survival ≥3 months.

• Adequate organ function: 1) Blood system (no blood transfusion or hematopoietic stimulating factor treatment within 14 days) : absolute neutrophil count (ANC) ≥1.5×109/L, platelet count (PLT) ≥90×109/L, hemoglobin (HGB) ≥90 g /L; Liver function: total bilirubin (TBIL) ≤1.5 times the upper limit of normal (ULN), except for Gilbert syndrome; Aspartate aminotransferase (AST) and alanine aminotransferase (ALT) ≤3.0 times ULN, liver metastasis or liver cancer patients need AST and ALT≤5.0 times ULN. 3. Renal function: serum creatinine (Cr) ≤1.5 ULN; If creatinine Creatinine clearance (Ccr) ≥50 ml/min (calculated by Cockcroft-Gault formula) was required at 1.5 ULN. Coagulation function: prothrombin International Normalized ratio (INR) ≤1.5 ULN, activated partial thrombin time (APTT) ≤1.5 ULN.

⁃ Eligible patients (male and female) who are fertile must agree to use a reliable contraceptive method (hormonal or barrier method or abstinence) with their partner during the trial period and for at least 6 months after the last medication; Women of reproductive age must have a negative blood or urine pregnancy test 7 days before first use of the study drug.

⁃ Subjects must give informed consent to the study prior to the study and voluntarily sign written informed consent.