Effect Of Sunitinib In A Patient With Primary Imatinib-Resistant Gastrointestinal Stromal Tumor.

e23516 Background: For newly diagnosed small intestinal GIST with hepatic metastases, imatinib (IM) resistance is sometimes seen during targeted therapy preoperatively. Subsequent treatment preferring to escalated IM dose or switch to sunitinib (SU) is not that clear in Chinese. Methods: Summarize a newly diagnosed case of small intestine GIST with hepatic metastases. In June 2014, the patient firstly visited to our hospital with the main complaint, abdominal pain with fever for 6 months. Basic test showed mild anemia, OB (+), ESR 51mm/h (normal 0-5). Abd and pelv enhanced CTshowed a low density area about 4.7 cm in hepatic VI Seg and another 1.0 cm in V Seg, and the 6th group of SI wall thickened with enhancement. MDT suspected it as SI-GIST, and a CT-guided liver biopsy was followed. Histological results confirmed the lesion as a metastatic GISTs (mitotic 5/10HPF) with IHC: CD117 (+), CD34 (-). Therefore, imatinib (IM) was prescribed as 400mg per day. Two months later, CT indicated primary imatinib resistance. We prescribed SU 37.5 mg per day orally for 1 month. And the CT implied positive SU response. 4 months after SU, CT showed a further reduction in SI as well as in VI Seg, while slightly increase in V seg. After SU for 6 months, partial small bowel resection and liver metastases resection (VI and V Segment) were performed on April, 2015. Results: Pathological results indicate that lesions in SI is GIST with metastases, 8x9x5 cm in size and mitotic count is 2/50 HPF after TKIs, and pelvic nodules and masses on liver V and VI seg are metastatic GIST (1-2/50 HPF). IHC results showed that SI mass is CD117 (+), CD34 (partial +), DOG (+), pelvic nodules, V and VI segment are CD117 (+), DOG-1 (+) . DNA testing shows that mass on SI has a KIT 9 exon ins-mutation, as well both of masses on liver V and VI seg are KIT 9 exon ins. Leukopenia and mouth ulcers occurred 2 months after surgery, and symptomatic treatment can manage these side effects. CT was performed every 3 to 6 months. No signs of recurrences in the liver and pelvis were found until Jan, 2018. Conclusions: For newly diagnosed SI-GIST with hepatic metastases, timely switching to SU after neoadjuvant primary IM-resistance may effectively control the disease in the long term.