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.