Robotic Duodenal Sleeve Resection for Gastrointestinal Stromal Tumor with Rare Exon 8 KIT Mutation Following Neoadjuvant Imatinib

In this video, we demonstrate a rare form of a gastrointestinal stromal tumor and its unique management. Gastrointestinal stromal tumors or GIST are most commonly found in the stomach, followed by the small intestine. Only 5%though are found in the duodenum.

GIST commonly harbor mutation in the receptor tyrosine kinase. Most commonly KIT Exons 9, 11, 13 and 17 or in PDGFRA. However, 10 to 15%have no detectable mutation in the most commonly tested KIT exons, and are thought to have no response to targeted therapies such as tyrosine kinase inhibitors, making them an important consideration for treatment.

Our case is a 73-year-old male with no significant past medical history. He underwent an EGD and colonoscopy for symptomatic anemia at an outside facility. A large lobulated mass was identified near the ampula of Vater.

Biopsies were negative for malignancy. Repeat EGD and EUS at our facility showed a mass originating from the muscularis propria opposite and one centimeter distal to the ampula. Biopsies were consistent with the GIST.

However, mitotic count could not be determined at that time due to small sample size. Staging imaging was performed and showed a clinical T2 tumor isolated to the duodenum. Genetic testing was then obtained for two reasons.

First being we were unable to fully risk stratify the patient without a mitotic count. Second, the tumors close proximity to the ampula would likely require a pancreaticoduodenectomy for resection. However, presence of a mutation sensitive to targeted therapies may allow shrinkage of the tumor in a more limited resection.

Initial testing was negative for common KIT mutations, but additional testing showed a rare exon 8 mutation. Few reports exist of exon 8 mutations in GIST, but one in vitro study suggests that tumors may be sensitive to the tyrosine kinase inhibitor imatinib. After a thorough discussion with the patient, imatinib was started.

On the left, you can see the patient's initial staging CT with repeat on the right six months after therapy. A 30%reduction in tumor size was noted, and we decided to perceive a surgery. We chose a minimally invasive robotic approach in an effort to minimize postoperative recovery time and expedite resumption of adjuvant oncologic therapy.

Here is a schematic of port placement for the robotic approach. After entry into the abdomen, a generous Kocher maneuver was performed to mobilize the duodenum. During this time, we encountered the lobulated mass.

We freed the lateral aspects of the mass from the surrounding attachments, which allowed us to further mobilize the duodenum. As we continued to mobilize the duodenum, we came to the ligament of Treitz. We divided the ligament of Treitz in order to pull the proximal duodenum toward the right upper quadrant.

A mesenteric window was made using the ligature. The bowel was then divided using an Endo GIA stapler with a 60 millimeter purple load. The ligature was then used to divide the proximal mesentery.

As we reached the mass, there were numerous retroperitoneale attachments that required lysis. We continued proximal to the mass until we were able to fit an Endo GIA stapler well past the proximal margin of the tumor. Again, a 60 millimeter purple load was used to divide the proximal duodenum.

In order to confirm the biliary system remained intact after resection, the gallbladder was mobilized and the cystic duct incised, allowing for insertion of the Fogarty catheter. As we advanced the Fogarty catheter, we could see the movement within the duodenum. An enterotomy was also made in the duodenum, and the presence of the Fogarty catheter was again confirmed.

This meant that the duodenal resection was sufficient and the patient would not require the more morbid pancreaticoduodenectomy. The duodenum and transected jejunum were approximated with stay sutures and an enterotomy was made in the jejunum. An Endo GIA stapler was used to make the common enterotomy.

A running 3-0 V-Loc suture was then used to close the common enterotomy. Interrupted 3-0 silk lumber sutures were also placed. The cystic duct was divided and the gallbladder was then removed.

The patient's recovery was largely unremarkable. He was advanced gradually to a regular diet, and his pain was well controlled. He was discharged on postoperative day five, and he had no postoperative complications.

Final pathology revealed a 4.3 by 4 by 2.1 centimeter GIST, grade one with one mitosis for five millimeters squared. All margins were negative. The patient was started on adjuvant imatinib five weeks postoperatively, and is now over three years without evidence of recurrence on active surveillance.