The pathological types of SMTs are complex, but most of them are benign, while only a few are malignant. Gastrointestinal stromal tumor (GIST) is a tumor with certain malignant potential, but its malignant potential depends on its size, location, and type [13]. GIST with a diameter of less than 2 cm has a low risk of malignancy, and the treatment recommended in the guidelines is controversial[2, 13]. For GIST larger than 2cm, surgical treatment is recommended due to its high risk of malignancy[2, 13, 14]. In our study, 13 of 26 lesions were determined to be GIST, and only 5 of them were larger than 2 cm. Considering that both endoscopy and EUS are invasive examinations, and long-term follow-up will pose a significant economic burden, most patients who came to our center hope to undergo endoscopic resection even if small SMTs were found during the examination process.
Clinically, lesions of the gastrointestinal tract which originate from the MP layer, closely adhere to the serous layer or grow outside the cavity are the surgical indications of EFTR. Studies have shown that exposed EFTR can treat the lesion originated from MP of the stomach with good safety and efficacy[15–17]. But for the colorectal lesions, the studies were mainly focused on the non-exposed EFTR. The full-thickness resection device (FTRD) of the colorectal non-exposed EFTR can remove the lesions after the OTSC closes the wound, but it is limited by the size of the lesion, and is mainly applicable to complex adenoma, early adenocarcinoma and SMT with a diameter of < 2.0 cm[18]. Schmidt et al[18] reviewed 25 cases of colorectal EFTR treated with FTRD, of which 2 cases were colon SMT, with a complete resection rate of 75.0% (18/24). And, 1 patient was unable to use the FTRD device due to sigmoid stenosis. There were no significant adverse events happened. Subsequently, many studies have suggested that non-exposed EFTR is safe and effective in the treatment of colorectal lesions, but the lesions involved in the study are mostly mucosal lesions, and there are only a few reports of submucosal tumors[11, 19]. In our study, we demonstrated a total technical success rate of 100% for exposed EFTR on treatment of colorectal SMTs. The median tumor diameter was 13.5(8.5, 20.0) mm. And, 9 of 26 lesions were larger than 2 cm, which may suggest that exposed EFTR may not be limited by the size of the lesion as non-exposed EFTR. Additionally, lesions located in the ileocecum, sigmoid, and lower rectum were considered as technical difficult location for EMR or ESD, which is associated with high risk of adverse event or long procedure time[20]. In our study, 8 lesions located in the anatomically difficult part. All these lesions were removed completely without adverse event. Therefore, we supposed that compared with non-exposed EFTR, ESD and EMR, exposed EFTR were further extended the indication of endoscopic treatment for SMTs. It is worth noted that exposed EFTR require a high level of endoscopic treatment techniques, and the surgeons performing the procedures in our study were all expert with extensive experience in endoscopic treatment.
During the exposed EFTR procedure, physicians should pay more attention to the prevention of air and fluid leakage as well as the completeness of wound closure. Metal clip suturing is the most basic suturing technique for EFTR intraoperative wound closure. As the span of metal clamps is limited, the perforation cannot be closed at one time for larger wound. So, the Chinese guideline recommends "suction-clamping suture", which means to suction the gas in the lumen of the digestive tract to sufficiently reduce the perforation, and then use multiple metal clamps to close the perforation[21]. Alternatively, a double-clamp endoscope can be used to reinforced the suturing with nylon string using a "string suture" method[21]. In recent years, the development of novel techniques such as over-the-scope clip and OverStitch suture for repairing GI injuries and managing bleeding will further promote the use of EFTR techniques[22]. Among our study, 13(50%) surgical wounds were sutured by metal clip and 13(50%) were sutured with Metal clips combined with nylon cord.
Literatures reported that postoperative bleeding rate of EFTR with FTRD were 2.2%-4.5%[10, 18, 23]. The common complications were post-polypectomy syndrome with abdominal pain, fever and signs of inflammation on blood chemistry tests of which the accident rate was 1.7%-8.9%[7, 10, 18]. In our study. only one patient (3.85%) whose lesion sized 10mm and located in cecum suffered from postoperative perforation and transferred to perform exploratory laparotomy to repair the defect. And, 3 of the 26 patients were suffered from post-polypectomy syndrome (11.54%). 1 patient were suffered from postoperative bleeding and performed emergency endoscopic hemostasis. All patients improved after treatment, and no patient died because of the adverse events. Compared with the previous study, we supposed that adverse events in our study were acceptable.
Our study still has some limitations. The sample size of our study is still insufficient for factor regression analysis. Moreover, our study was included two centers’ data for analysis. It’s necessary to carry out a multi-center study with large sample for further analysis of the safety and efficacy of exposed EFTR.
In summary, exposed EFTR of colorectal SMTs have a reliable efficacy and the complication rates are acceptable. Therefore, exposed EFTR as a treatment of colorectal SMT considered to be safe and effective, but adequate preoperative evaluation should be done, and the procedure should be conducted by expert with sufficient experiences.