Selective Internal Radiation Therapy (SIRT) for Gist Liver Metastases Resistant to Tyrosine Kinase Inhibitors

ABSTRACT Background and aim The liver is the typical location of metastases from gastrointestinal stromal tumors (GIST). Usually, metastases of GIST are treated by tyrosine kinase inhibitors (imatinib, sunitinib or others). In patients with multiple metastases resistant to drugs and not amenable to surgical resection interventional ablation techniques are considered. Selective internal radiation therapy (SIRT), delivering 90Y-loaded particles to liver metastases might offer a new treatment option. Material/methods We evaluated nine patients with liver metastases of GIST being progressive under drug (TKI) treatment and referred for SIRT. Five patients had liver metastases only, in another four patients extrahepatic disease was present but controlled by TKI therapy. One patient had to be excluded from treatment due to a hepato-pulmonary shunt volume exceeding 20 %. Depending on intrahepatic tumor distribution, either both liver lobes or one lobe were treated using 90Y spheres. Follow-up was done via dynamic MRI, contrast-enhanced (CE)-CT and 18F-FDG-PET-CT using modified RECIST criteria at 3 months intervals. All patients with targetable mutations in KIT or PD continued with drug to control extrahepatic tumor spread. Results In the eight patients, fourteen liver lobes were treated with a mean activity of 1.07GBq per lobe. No severe side effects occured in 7/8 patients, while one male developed an ulcer of the stomach not responding to high dose antacid therapy. Radiation induced liver disease (RILD) was not observed. Three patients showed a complete remission (CR) whereas four other patients developed a partial remission (PR) and two patients had to be classified as stable disease (SD). Median follow-up interval is 16 months (range, 4 - 52 months). The mean progression free interval regarding hepatic disease was 9,6 months. Conclusion SIRT offers a safe and effective treatment option in patients with liver metastases from GIST being progressive under TKI treatment. Disclosure All authors have declared no conflicts of interest.