LST is closely associated with colorectal carcinoma, and studies have revealed that LST is highly likely to transform into malignancy [9]. In our study, the risk for high-grade dysplasia and carcinoma in this study was 39.7%, including 25.3% for high-grade intraepithelial neoplasia, 14.4% for cancer, including 4.3% of mucosal cancer, 5.3% of sm1 submucosal invasion and 4.8% of sm2 submucosal invasion. Previous studies showed that the incidence of HGIN was 20.9–35.2%, and that the incidence of submucosal invasive carcinoma ranged from 2.6–12.3% [10]. Previous studies have shown that LST subtype, lesion size, non-lifting sign are significantly linked to high-grade dysplasia and carcinoma [9]. In our study, univariate and multivariate analysis revealed that male, diameter of lesion ≥ 30 mm, and endoscopic phenotype of LST-G-M and LST-NG-PD were key risk factors for the occurrence of high-grade dysplasia and carcinoma in LST, indicating that larger LST-G-M and LST-NG-PD have higher risk of malignant transformation. The risk of LST becoming malignant is connected to the endoscopic morphological type and that the risk differs among different subtypes. Studies have reported that non-granular LST has a higher risk of being malignant and SM invasion than granular LST [11, 12]. Moreover, dynamic observation of lesions reveals that flat lesions have a higher risk of malignancy than elevated lesions [13, 14]. Therefore, this kind of lesion should be treated as early as possible.
The kind of surgical method used is based on the size of the lesion, and the success of the surgery is dependent on how surgeons operate and their skills. For LST lesions < 2 cm in diameter, EMR can be used because it is simple, safe, and effective. EPMR can be performed on LST > 2 cm in diameter; however, there is a risk of a residual lesion and recurrence [15, 16]. ESD has a higher rate of en bloc resection and a lower risk of local residual tumor and recurrence than EMR and EPMR. As a result, ESD is a preferred treatment method for larger LST lesions. The en bloc resection rate of colorectal tumors by ESD in large medical centers in China ranged from 83.7–97.5%, the R0 resection rate was 82.8–90.1% [11, 17]. In our study, the en bloc resection rate of LST lesions was 96.3%, and the R0 resection rate was 93.3%. The above results were basically consistent with those reported in the domestic literature. Nevertheless, the shortcomings, such as the lengthy surgical time of ESD and the difficulty of the procedure, require surgeons to be experienced in ESD and to be able to deal with complications in a timely and accurate manner.
Submucosal invasion of LSTs is divided into superficial submucosal carcinoma and deep submucosal carcinoma according to the depth of invasion. Metastatic lymph nodes are rarely found in superficial submucosal carcinoma cases [18]. Moreover, the lesions can be curatively resected endoscopically. Nevertheless, deep submucosal invasion lesions need surgical intervention [9, 19]. The Japanese Society for carcinoma of the Colon and Rectum (JSCCR) guidelines classify submucosal invasive carcinoma into sm1 (< 1000um or head invasion) and sm2 (≥ 1000µm or pedicle invasion) [5]. Since the risk of the metastatic lymph node is higher for sm2, additional surgical procedures were required. In our study, all sm2 carcinoma and part of sm1 carcinoma with vessel tumor embolus and lesion invading the basal margins performed additional surgery. Postoperative pathological findings revealed a perienteric metastatic lymph node. The patients underwent colonscopy and the results showed no recurrence throughout the follow-up. Our univariate and multivariate analysis suggested that LST-NG-PD subtype and tumor budding were risk factors for submucosal invasion. In addition, the tumor budding was an independent risk factor for deep submucosal invasion. The present study revealed that larger lesions were more likely to become high-grade dysplasia/carcinoma, smaller lesions were also at risk of becoming cancerous, even submucosal invasion or deep submucosal invasion. The evaluation of pathological invasion depth and incisal margin after LST treatment through endoscopy is critical for clinical treatment and patient prognosis. After the analysis of the data from cases of invasive carcinoma in the study, lesion size cannot be used alone to determine whether the tumor has penetrated into the mucosal layer or the deep submucosa, LST-NG-PD was an independent risk factor for predicting submucosal infiltration before ESD surgery, postoperative pathological tumor budding was an independent risk factor for deep submucosal infiltration. Magnification endoscopy and ultrasound endoscopy are now widely used in minimally invasive treatment and can help to initially examine and judge the nature of LST lesions, the presence of carcinoma, and the depth of invasion [20]. Nonetheless, postoperative pathological results remain the only method to measure the depth of invasion, the presence of vascular invasion, and the cleanliness of the incisal margins [12, 13].
The most common complications of LST during an endoscopic procedure are bleeding and perforation [21]. In our study, the postoperative delayed bleeding rate was 2.1%, the perforation rate was 4.8%. In both domestic and international studies, the rate of delayed bleeding ranged from 2.3–11.9% [22], the frequency of postoperative perforation ranged from 2.3–4.9% [16, 22]. The risk of postoperative bleeding and perforation was closely related to the size of the lesion, the type of lesion, endoscopic resection and the experience of surgeons [23]. It is generally believed that the larger the postoperative wound, the greater the probability of complications such as delayed bleeding and perforation, and the slower the wound heals [24]. Our study suggested that the complications mostly happened during or postoperative ESD. Logistic analysis indicated that right colon, LST-G-M and size ≥ 30mm were risk factors for complication during endoscopic treatment of colorectal spreading tumors. As a result, proper management of postoperative wounds is the key to preventing complications. Studies have shown that early intraoperative diagnosis of small perforations and effective closure of the wound by clips via endoscopy can help the wound heal, which can significantly reduce the incidence of postoperative complications and decrease the need for additional surgeries [25].