How can endoscopic R0 resection be ensured for relatively small gastric gastrointestinal stromal tumors?

Endoscopic resection of gastrointestinal stromal tumors (GISTs) has been reported in some clinical studies [1] [2] [3] [4]. These studies involved GISTs with an average size smaller than 2 cm, and demonstrated high en bloc resection rates, low recurrence rates at short-term follow-ups, and low risk of postoperative complications. The resection methods used in these studies mainly included endoscopic submucosal excavation (ESE), endoscopic band ligation (EBL), endoscopic submucosal dissection (ESD), and endoscopic full-thickness resection (EFTR). The results of these studies suggested that relatively small GISTs can be safely removed by endoscopic resection.

However, the R0 resection rate and long-term effectiveness of endoscopic resection of GISTs remain unclear. Most of the studies did not mention margin-negative R0 resection, and it was not clear whether the margins of resected tumors were pathologically negative or not. In addition, the studies reported only relatively short follow-ups. One study has suggested that stromal tumors typically recurred within 5 years after surgical removal while they rarely recurred over 10 years after surgery [5]. Therefore, the long-term effect of endoscopic resection of GISTs needs to be assessed.

Meining envisioned the concept of “the ability to work from within the lumen in the same way that a surgeon does in the abdominal cavity” [6]. If such an idea were to be realized, the issues related to endoscopic resection of GISTs, including the inherent risk of incomplete resection, peritoneal implantation due to tumor rupture, and difficulty in repairing any incidental perforation, would probably be easily resolved, and such an endoscopic platform would be helpful in the resection of large GISTs. However, for the resection of large tumors, to date, there is no reliable endoscopic platform that allows us to overcome all these difficulties.

Nevertheless, relatively small GISTs can be safely removed by endoscopic resection, as suggested by existing clinical studies. Perforations of the gastrointestinal (GI) tract can be effectively closed using titanium clips, nylon cord, and over-the-scope clips (OTSCs). A systematic review conducted in 2015 demonstrated that endoscopic closure of acute perforation of the GI tract is safe and effective: among the 183 cases of gastric perforation, 179 (98.4 %) were successfully treated by endoscopic closure [7]. Thus, there is no major obstacle to treatment of perforation after full-thickness resection of relatively small stromal tumors.

After safe resection of the tumor and successful closure of perforation can be ensured, in order to achieve R0 resection of GISTs, another requirement is to reduce the damage to the tumor surface during resection. This may be similar to the principle that holds in the laparoscopic or surgical removal of stromal tumors: the tumors should be completely resected without damage to their surfaces, and the resected tumors should be covered with complete capsules and some mucosal tissues. However, this principle is not emphasized in the endoscopic resection of GISTs. In ESE, EBL, ESD, and EFTR procedures, the submucosa and muscularis propria may be dissected very close to the tumor, making it difficult to avoid damage to the tumors. ESD procedures in particular could very easily injure the tumor surfaces. Thus, to ensure R0 resection, it may be necessary that full-thickness resection of GISTs should be done along their margins after the tumors are fully exposed, regardless of whether they are located in the deep layer or the superficial layer of the muscularis propria; this would reduce as much as possible the damage to the tumor surface caused by dissection very close to the tumor. This practice might help to improve the long-term effectiveness of endoscopic resection of GISTs and assure R0 resection.

At present, the feasibility of safe endoscopic resection of small GISTs and effective closure of gastric perforation has been proven to some extent. However, to potentially ensure R0 resection of GISTs, we may need to emphasize a concept of resection that is similar to the laparoscopic and surgical principle of completely resecting the fully exposed tumor along its margins without damaging its surfaces. In addition, pathological assessments of R0 resections and long-term follow-ups are needed to further verify the effectiveness of endoscopic resection of GISTs.

• References

• 1 Shen C, Chen H, Yin Y et al. Endoscopic versus open resection for small gastric gastrointestinal stromal tumors: safety and outcomes. Medicine (Baltimore) 2015; 94: e376
• 2 Huang LY, Cui J, Liu YX et al. Endoscopic therapy for gastric stromal tumors originating from the muscularis propria. World J Gastroenterol 2012; 18: 3465-3471
• 3 Bai J, Wang Y, Guo H et al. Endoscopic resection of small gastrointestinal stromal tumors. Dig Dis Sci 2010; 55: 1950-1954
• 4 Sun S, Ge N, Wang C et al. Endoscopic band ligation of small gastric stromal tumors and follow-up by endoscopic ultrasonography. Surg Endosc 2007; 21: 574-578
• 5 Joensuu H, Vehtari A, Riihimaki J et al. Risk of recurrence of gastrointestinal stromal tumour after surgery: an analysis of pooled population-based cohorts. Lancet Oncol 2012; 13: 265-274
• 6 Meining A. Endoscopic full-thickness resection: the logical step toward more extended endoscopic oncologic resections?. Endoscopy 2015; 47: 101-102
• 7 Verlaan T, Voermans RP, van Berge Henegouwen MI et al. Endoscopic closure of acute perforations of the GI tract: a systematic review of the literature. Gastrointest Endosc 2015; 82: 618-628