Endoscopic submucosal dissection versus transanal local excision for rectal carcinoid: a comparative study

In this work, we compare the short-term clinical outcomes between endoscopic submucosal dissection (ESD) and transanal local excision (TALE) for rectal carcinoid tumors, so as to help surgeons decide which method should be chosen for these patients.

Rectal carcinoid tumors account for 18.5 % of all carcinoid tumors. Although these tumors represent only 1.3 % of all rectal neoplasms, their incidence is drastically increasing [1, 2]. These tumors can show a broad range of clinical behavior, from benign and asymptomatic to disseminated and metastatic [3]. Because rectal carcinoid tumors often present as small and localized tumors that rarely recur after resection, rectal carcinoid tumors have the best prognosis among all carcinoid tumors with a 5-year survival rate at 88.3 %, and thus have usually been managed with local excision [4‐6].

For rectal carcinoid tumors not amenable to conventional colonoscopic removal, the alternative treatment option is TALE procedure. This local procedure has proved to be safe and effective in the treatment of low rectal lesions. However, TALE approach must be performed with the patient under anesthesia, such as spinal anesthesia, general endotracheal anesthesia (GETA), and IV sedation + local depending on tumor location and size, especially the characteristics and comorbidities of patients.

ESD is a novel colonoscopic method that enables en bloc resection for colorectal lesions. It can be performed with patients without anesthesia. The ESD approach has a reported perforation rate of 2 to 10 %, an en bloc resection rate of 80 to 90 %, and a short-term recurrence rate for colorectal ESD of 0 to 2.1 % [7].

In the traditional sense, the indications of TALE for rectal carcinoid tumors are as follows: (1) tumor located less than 7 cm to anal edge, (2) tumor size accounted less than 1/3 lumen diameter, (3) tumor node metastasis (TNM) staged earlier than T1. Except the above situation, choose surgical oncologic resection. Despite a growing understanding of the clinical effectiveness of local excision for small rectal carcinoid tumors, there is still controversy concerning the best surgical choice for rectal carcinoid tumors with different diameters [8]. The aim of this study is to report our experiences of adopting two different local excision procedures according to tumor diameter. To our knowledge, there is no report about the surgical strategies and results of ESD and TALE for rectal carcinoid tumors.

The baseline characteristics of the two groups were shown in Table 1. The two groups did not differ in terms of age, sex, or distance from anal verge. The mean size of tumors was significantly bigger in the TALE group (0.8 ± 0.2 versus 1.1 ± 0.5 cm; P = 0.018). En bloc resection was achieved for 30 patients (97 %) in the ESD group and all the patients in the TALE group.

Operative time was longer in the TALE than in the ESD group (40.0 ± 22.7 min versus 12.2 ± 5.3 min; P < 0.001). Complications in the TALE group were five cases of AROU. There were no bleeding or perforation cases in either group. Table 2 summarizes procedure-related parameters.

Follow-up data was available in 24 patients in the ESD group because seven patients were not due for follow-up at the time of analysis. One patient underwent additional surgery (TALE) after ESD because the ESD specimen showed positive resection margin. Follow-up data was analyzed in 18 patients in the TALE group. The median follow-up period was 16.4 months (range 8–31 months) in the ESD group and 28.4 months (range 8–68 months) in the TALE group. The median number of follow-up colonoscopies was 1.9 times (range 1–4 times) in the ESD group and 2.5 times (range 1–5 times) in the TALE group. There was no local recurrence or distant metastasis in any patients in either group during the follow-up period.

Rectal carcinoid tumor is a rare condition accounting for only 1.3 % of the overall rectal tumor cases [10, 11]. Tumor size has been a known prognostic factor for rectal carcinoid tumors. ESD, TALE, and radical resection have been performed as treatments of rectal carcinoid tumor. However, it is currently difficult to decide between treatments such as local excision and radical surgery, especially for tumors that are >1 to ≤2 cm in diameter. It appears that small rectal carcinoids <1 cm in size can be safely managed by local excision. For tumors >1 to ≤2 cm, local excision is usually recommended, but radical surgery should be considered if there is evidence of lymph node metastasis [12]. The preoperative radiological evaluation of lymph node metastasis was critical. Pelvic imaging evaluation such as CT or endorectal ultrasound was made, and no enlarged lymph nodes were found in our patients before surgery.

ESD and TALE are performed for local excision of rectal carcinoids in daily clinical work. Which is the best method for the local resection of rectal carcinoids? Son et al. reported pathologically determined complete-resection (P-CR) rates for small rectal carcinoid tumors excised by using several methods. The P-CR rates were 30.9, 72.0, and 81.8 % for a conventional endoscopic polypectomy, ESD, and TALE [13]. TALE is a traditional procedure for treating lower rectal tumors and provides deeper vertical resection margin. Kim et al. [14] described the complete-resection rate for transanal surgery as over 97 %. Recently Son et al. reported that the pathologically complete-resection rates were 30.9, 72.0, and 81.8 % for conventional polypectomy, advanced endoscopic techniques, and surgical local excision, respectively. Pathologically complete-resection of small rectal carcinoid tumors was more likely to be achieved when using surgical local excision [14]. Ono et al. [15] described results obtained with 14 rectal carcinoid tumors treated by ESD between 1999 and 2002. All tumors were completely resected, and no recurrence was noted at a median follow-up of 10.5 months. In our study, the mean tumor size was 1.1 ± 0.5 cm and 0.8 ± 0.2 cm in TALE and ESD group, respectively. All lesions were confined to the submucosal layer. The pathologically complete-resection rates were 97 and 100 % for ESD and TALE, respectively. The results suggested that pathologically complete resection of rectal carcinoid tumors can be achieved when using proper procedure according to the tumor size.

However, TALE must be also considered to be more invasive because of the risk associated with the use of anesthesia [14]. Spinal anesthesia is a risk factor for acute retention of urine (AROU). In fact, anal dilation or retraction because of operation may cause anal pain and also may result in AROU. These factors explain why the TALE group had a significantly higher incidence of AROU. On the other hand, ESD is performed without anesthesia, and there is no need to dilate the anal sphincter. This may account for the lower morbidity rate and shorter operative time in the ESD group.

But for a local recurrence case, TALE may be more appropriate. ESD was performed after a mixture of glycerin and fructose, normal saline, adrenaline, and methylene blue was injected into the submucosal layer in order to achieve en bloc resection and avoid perforation. However, the lesion cannot be lifted after injection because of the existence of fibrosis in the submucosal layer in the case of local recurrence. The cut and the dissection steps that use cutting devices may be technically difficult. Fujishiro et al. reported that endoscopic en bloc resection was not achieved in some colorectal tumors because of fibrosis which prevented a sufficient submucosal fluid cushion in the submucosal layer [16]. In the TALE group, one patient had a reoperation because of positive resection margin with ESD. By TALE procedure, the tumor was removed with R0 resection. From our opinion, TALE may be a safe and effective method in the treatment of scar embedded lesion.

This study had some limitations. First, this was a retrospective study. We were unable to fully evaluate possible confounders, owing to the retrospective nature of this study. The second limitation of this study was that further follow-up studies are required to more accurately define the long-term outcomes of TALE and ESD. The third limitation of this study was the limited presented data and the number of patients enrolled. It is because the disease incidence is low that there is a difficulty of achieving an adequate number of cases for comparative analysis. Best results should be achieved with work with more patients and preferably a multicenter.

In conclusion, for the treatment of rectal carcinoid tumors with diameter <1 cm, ESD has better short-term clinical outcomes than TALE in terms of faster recovery and possibly a lower morbidity rate. TALE may be the first therapeutic choice of scar embedded rectal carcinoid tumors. Prospective studies with larger samples are needed to validate the benefits of TALE.

AROU, acute retention of urine; P-CR, pathologically determined complete resection; CT, computed tomography; EUS, endorectal ultrasonography; ESD, endoscopic submucosal dissection; TALE, transanal local excision; GETA, general endotracheal anesthesia; TNM, tumor node metastasis.