Disitamab Vedotin Combined With Sintilimab as First-line Treatment of Elderly Patients With Gastric Cancer

Inclusion Criteria:

* 1\) Volunteer to take part in the study ;
* 2\) Age ≥65 , male or female;
* 3\) Gastric cancer or adenocarcinoma of gastroesophageal junction confirmed by histology and/or cytology;
* 4\) Have not received systematic treatment; If the subject has received adjuvant therapy after completing radical treatment for early gastric cancer and the subject has relapsed disease, ensure that the end of adjuvant therapy is more than 6 months from the first dose of the study and that various toxicities due to the adjuvant therapy have recovered.
* 5\) The HER2 immunohistochemistry (IHC) test result is IHC 3+or 2+, and the previous test results of the subject (confirmed by the investigator) are acceptable;
* 6\) At least one assessable lesion (RECIST 1.1 );
* 7\) Expected survival time ≥ 6 months;
* 8\) ECOG 0-2;
* 9\) If the main organs function normally, they meet the following standards:

Blood routine examination (no blood transfusion and G-CSF use within 14 days before screening):

1. Hemoglobin ≥ 90 g/L;
2. Absolute neutrophil count (ANC) ≥ 1.5 × 109/L；
3. White blood cell count ≥ 3.0 × 109/L；
4. Platelet count ≥ 80 × 109/L；

   Blood biochemical examination (albumin was not used within 14 days before screening):
5. Albumin ≥ 28 g/L;
6. Total bilirubin ≤ 2 × Upper limit of normal value (ULN);
7. In the absence of liver metastasis, aspartate aminotransferase (AST), alanine aminotransferase (ALT), alkaline phosphatase (ALP) ≤ 2.5 × ULN； ALT, AST and ALP ≤ 5× ULN in case of liver metastasis ；
8. Alkaline phosphatase (ALP) ≤ 5 × ULN；
9. Creatinine ≤ 1.5 × ULN； Or the creatinine clearance rate (CrCl) calculated by Cockcroft Gault formula is ≥ 50 mL/min;

   Coagulation function:
10. International normalized ratio (INR) or prothrombin time (PT) ≤ 1.5 × ULN；

j) Activated partial thromboplastin time (APTT) ≤ 1.5 × ULN。

Exclusion Criteria:

* 1\) Have a history of malignant tumors other than gastric cancer, except for the following two cases:

  1. The patient has received possible curative treatment and there is no evidence of the disease within 5 years;
  2. The resected skin basal cell carcinoma, skin squamous cell carcinoma, superficial bladder cancer, cervical carcinoma in situ and other carcinoma in situ were successfully received;
* 2\) Have received allogeneic stem cells or solid organ transplantation in the past;
* 3\) Patients who have received other anti-tumor systemic therapy in the past (including traditional Chinese medicine with anti-tumor indications), and have been less than 4 weeks from the completion of treatment to the administration of this study, or the adverse events caused by previous treatment have not recovered to ≤ CTCAE level 1 (except hair loss and pigmentation);
* 4\) Previous or current congenital or acquired immunodeficiency disease;
* 5\) Allergic to the study drug;
* 6\) Other significant clinical and laboratory abnormalities, which the researchers think affect the safety evaluation;
* 7\) Serious infection in active period or poorly controlled clinically;
* 8\) Not recovered from the operation;
* 9\) Pregnant or lactating women, and women or men with fertility who are unwilling or unable to take effective contraceptive measures;
* 10\) Other situations that the investigator thinks are not suitable for inclusion.