The study is to investigate the efficacy and safety of apatinib for the first-fine treatment in elderly patients with locally advanced or metastatic adenocarcinoma of stomach or gastroesophageal junction, unable or unwilling to chemotherapy, through progression-free survival (PFS). Apatinib will be given to patients with an efficacy assessment of stable disease (SD), partial response (PR), or complete response (CR) every 2 cycles. Patients were assigned to 500 mg/d apatinib continually until disease progression or intolerable toxicity or patients withdrawal of consent. The dose of apatinib may be decreased to 250 mg/d following the occurrence of a clinically significant adverse event (AE). Treatment will be discontinued if the subject is unable to tolerate a daily dose of 250 mg, and the sample size is about 30 individuals. Tumor tissue samples will be collected from each enrolled subjects before the start of treatment, and detected using next generation sequencing (NGS)-based comprehensive genomic profiling. The potential biomarkers in predicting apatinib efficacy or safety will be explored.

Inclusion Criteria:

1. Patients with histologically proven primary locally advanced or metastatic gastric or gastroesophageal junction adenocarcinoma;
2. Age ≥ 65 years;
3. ECOG Performance Status: 0-2;
4. No previous anti-cancer therapy for the locally advanced or metastatic disease;
5. Unable or unwilling to chemotherapy;
6. At least one measurable lesion as defined by RECIST 1.1;
7. With acceptable hematologic, cardiac, hepatic, pulmonary and renal function;
8. Can take apatinib orally;
9. Life Expectancy: 3 months or more.

Exclusion Criteria:

1. History of other primary malignancy (except basal cell skin cancer or cervical carcinoma in situ);
2. Patients with un-controlled blood pressure on medication (> 140/90 mmHg);
3. Patients with other nonmeasurable disease such as un-controlled diabetes, severe cardiovascular and cerebrovascular diseases;
4. Patients with bleeding tendency, receiving thrombolytics or anticoagulants；
5. Patients with massive hydrothorax or ascites;
6. Patients with uncontrolled central nervous system (CNS) metastases;
7. Proteinuria 2+ or 24-hour urinary protein ≥ 1g;
8. History of drug addiction or abuse;
9. Patients cannot take apatinib orally for any reason;
10. Estimated life expectancy ˂ 3 months;
11. Current, recent (within 4 weeks prior to study entry), or planned participation in any other clinical trials;
12. Inability to understand and agree to informed consent.