The goal of this Mesylate apatinib versus standard second-line TKI in the treatment of advanced gastrointestinal stromal tumors: a randomized, open, controlled, single-center clinical study is to explore the efficacy and safety of Apatinib compared with second-line treatment in advanced GIST patients with first-line TKI failure. The main questions it aims to answer are:

• To explore the efficacy and safety of Apatinib compared with standard second-line treatment for GIST with advanced first-line TKI failure.
• To explore the expression level and MVD value of VEGFR2 in GIST, and to explore the relationship between the expression level and the location, size, mitotic image and recurrence risk grading of GIST.

Patients with advanced GIST were randomly included in the trial group and the control group at a ratio of 1:1.

The objectives of this study were as follows:

1. To explore the efficacy and safety of Apatinib compared with standard second-line treatment of advanced GIST with first-line TKI failure, and to provide high-level clinical evidence for the treatment of late-stage plasmatoma;
2. Explore the expression level and MVD value of VEGFR2 in GIST, and explore the relationship between the expression level and the location, size, mitotic image and recurrence risk grading of GIST.

Inclusion Criteria:

1. Patients were enrolled voluntarily and signed a written informed consent with good compliance and follow-up;
2. Age ≥18 years (calculated on the date of signing the informed consent) for both men and women;
3. Previous first-line TKI (Imatinib/Avatinib) therapy and eventual treatment failure (disease progression or toxicity intolerance during treatment);
4. Subjects who provide pre-C-Kit /PDGFRA test reporting can provide 10ml blood sample and fresh or archived tumor tissue for genetic testing.
5. ECOG score: 0 ~ 1;
6. Predicted survival ≥12 weeks.

Exclusion Criteria:

1. Previous molecular targeted therapy other than imatinib/Avatinib for the treatment of gastrointestinal stromal tumor;
2. Toxicity of previous imatinib/Avatinib treatment or other treatments has not recovered or reached NCICTCAE5.0≤ level 1;
3. Patients with clinical symptoms of ascites or pleural effusion who need puncture drainage or who have received thoracic and ascites drainage within 1 month before signing informed consent, except those who only show a small amount of ascites or pleural effusion without clinical symptoms;
4. A second primary malignancy within the last 5 years, except for basal cell carcinoma, squamous cell carcinoma of the skin, or carcinoma in situ of the cervix that has been adequately treated;
5. Gastrointestinal stromal tumor with central nervous system metastasis;
6. Inability to swallow, chronic diarrhea and intestinal obstruction, with multiple factors affecting drug administration and absorption.