The goal of this prospective study is to learn whether there is a synergistic effect when radiotherapy is combined with ripretinib in the treatment of patients with unresectable advanced GIST. It will also learn about the safety of this regimen.The main questions it aim to answer is: Dose radiotherapy combined with ripretinib prolong the time to disease progression for patients with advanced GIST?

ripretinib is the standard fourth-line treatment agent for inoperable advanced GIST patients, but the mPFS is only 6.3 months. Prolonging the time to TKI resistance by using a new treatment approach is important to increase the chances of surgery ,improve the survival time, and quality of life for patients. GIST was previously thought to be a tumor that was insensitive to radiotherapy, but a growing number of studies have shown that GIST is moderately sensitive to radiotherapy and that radiotherapy is effective in controlling the tumor. In our previous work, palliative radiotherapy was given to patients with advanced GIST after multiline drug resistance, and we achieved local control for nearly 2 years while significantly improving the patient's symptoms .

In recent years, radiotherapy technology has been continuously improved, and new radiotherapy techniques can be more precise and have less impact on surrounding organs, making it possible to increase the dose of radiotherapy. For large GIST, our research team has optimized the radiotherapy technique by using simultaneous integrated boost intensity-modulated radiotherapy technique, which can deliver a safe dose at the edge of the tumor while delivering a high dose of radiotherapy at the center of the tumor, ensuring safety and resulting in better therapeutic effects.

We proposed to select some patients with unresectable advanced GIST to explore the feasibility of radiotherapy combined with TKI for the treatment of advanced GIST after failure of first-, second-, and third-line drug therapies with simultaneous addition of radiotherapy to oral ripretinib treatment

Inclusion Criteria:

• Voluntary participation and signed informed consent;
• age: 18 to 75 years, Male or female
• Patients with histologically confirmed GIST and Imaging evaluated as unresectable recurrent and metastatic disease or locally advanced.
• ECOG Performance Score: 0-2
• Subjects who have progressed or documented intolerance after previous first-line, second-line, and third-line treatments.
• At least one measurable lesion in the abdominal or pelvic cavity that has progressed after frontline treatment
• Adequate organ function and bone marrow reserve

Exclusion Criteria:

• estimated life-expectancy less than 3 months.
• Patients who have received previous radiotherapy to the proposed radiotherapy site, or the tumor has significant mobility, poor tolerance of radiotherapy in adjacent organs, and who are considered unsuitable for radiotherapy after MDT discussion
• Any other clinically significant comorbidities, which in the judgment of the investigator, could compromise compliance with the protocol, interfere with interpretation of the study results, or predispose the patient to safety risks.
• If female, the patient is pregnant or lactating, or plans to become pregnant during the study treatment period