The outcome of local excision of large rectal polyps by transanal endoscopic microsurgery

Abstract

Introduction:

Local excision of large rectal polyps can be an alternative for radical rectal resection with total mesorectal excision. We aim to report the functional and oncological outcomes of transanal endoscopic microsurgery (TEM) for patients with large rectal polyps.

Methods:

All demographic and clinical data of patients who underwent TEM for rectal polyp of 5 cm or more at the Hasharon Hospital from 2005 to 2018 were retrospectively reviewed.

Results:

Twenty-eight patients were included. The mean age was 66 years. The mean polyp size was 6.2 cm (range: 5–8.5 cm) with a mean distance of 8.3 cm from the anal verge. Peritoneal entry during TEM was observed in five patients and additional laparoscopy after the completion of the TEM was performed in four patients. There were no major perioperative complications. Seven patients had minor complications. Final pathology revealed T1 carcinoma in five patients and T2 carcinoma in three patients. Re-TEM was performed in one patient with involved margins with adenoma. After a median follow-up of 64 months, one patient had local recurrence.

Conclusion:

TEM is an acceptable technique for the treatment of large polyps with minor complications and a reasonable recurrence rate. TEM may be considered regardless of the size of the rectal polyp.

INTRODUCTION

Adenomas of the rectum are a common condition, and the incidence of colorectal polyp is rapidly increasing worldwide.[1] All rectal adenomas should be excised since it is well established that a gradual increase in the size of the adenoma carries a parallel risk of malignant mutation and development of cancer, as part of the ‘adenoma–carcinoma sequence’.[2,3] Resection of rectal polyps includes local excision using: endoscopic mucosal resection (EMR), endoscopic submucosal dissection (ESD) and transanal excision. When endoscopic polypectomy is unsuccessful, the historical approach was radical rectal resection (anterior resection [AR] or abdominoperineal resection [APR]) with total mesorectal excision (TME).[4,5] Rectal resection by TME is the definitive surgery for rectal tumours, but this radical surgery holds excessive morbidity and mortality, with no added benefit for benign rectal lesions. Several transanal excision methods have proven much less morbid and oncologically safe for benign lesions and early cancer; one such method is transanal endoscopic microsurgery (TEM). TEM is more effective than TAE in achieving clear margins, resulting in a less fragmented specimen and associated with lower recurrence rates.[6] TEM is the best transanal technique and has many advantages over EMR[7] and ESD.[8,9] TEM has also demonstrated its effectiveness in treating early rectal cancer with favourable features and with no adverse pathologic findings.[10-12]

The traditional indications for transanal excision were for lesions within 8 cm of the anal verge, <3 cm in size and occupying <30%–40% of the circumference of the rectum.[13,14] With increasing surgeon experience, these formerly absolute contraindications have become relative. Some authors have advocated expanding the criteria for local excision to include not only benign lesions but any locally resectable T1N0 tumours.[15]

Resection by transanal endoscopic microsurgery for large lesions poses some problems

Technical obstacles include obtaining complete polyp resection, perforation of the rectum wall and entry to the peritoneal cavity during the procedure. Functional concerns include rectal stenosis and incontinence. Oncological issues include the presence of cancer in the polyp because large rectal polyps have higher probability cancer, and recurrence of the rectal polyp. The risk of recurrence after TEM is mitigated by the high repeatability of the procedure, as well as the satisfactory outcomes seen with salvage radical resection.

Few reports in the literature dealt with the excision of large rectal lesions by TEM.[16-19] We aim to report the outcome of patients undergoing TEM for large rectal polyps in our medical centre.

METHODS

Approval for this retrospective study was obtained from the Institutional Review Board of the Rabin Medical Center with a waiver of informed consent. All patients who underwent TEM procedures at the Hasharon Hospital, Rabin Medical Center from January 2005 to December 2018 were quarried. A large polyp was defined as a polyp larger than 5 cm.

Demographic and clinical and pathological data were retrospectively collected from electronic medical records. Among the variables collected were tumour dimension, location and polyp histology. Data regarding operative findings post-operative complications, and long-term outcomes were also collected.

Before surgery, patients underwent a pre-operative evaluation for TEM, according to a protocol that included full colonoscopy with biopsy, rigid proctoscopy to assess the tumour size, location within the rectal wall and distance from the anal verge and the number of lesions. Transrectal ultrasound was performed for lesions suspicious for cancer to assess the T stage.

The preparation for surgery in TEM patients was similar to the preparation of patients undergoing colon resection. It included mechanical bowel preparation on the day before the operation and administration of prophylactic antibiotics at the time of anaesthesia induction. The original Richard Wolf equipment was used to perform the procedure, and the procedure was performed according to the standard technique described by Buess et al.,[13] the detailed surgical technique of TEM is described elsewhere. The patients were placed in a prone jackknife or lithotomy position depending on the tumour location. The tumour was removed by full-thickness rectal wall excision with a 1-cm margin. The specimens were pinned and marked for orientation by the surgeon.

Closing methods of large rectal defects were the approximation of the edges of the defect by interrupted sutures. Suturing technique implemented is full-thickness transverse manner absorbable sutures. In the case of peritoneal entry, the closure of the defect was done in two layers with separate closure of the peritoneum when feasible. In the case of large rectal perforation, a laparoscopic exploration was done in order to visualise and explore the suture line of the rectal wall. Anastomotic leak testing was also performed.

All patients had a urinary catheter in place at the time of surgery, which was removed on the first day after surgery. Patients resume oral intake of a liquid and soft diet on the 1^st post-operative day and are subsequently advanced. Pain management included oral dipyrone or paracetamol, and narcotics as needed. Patients were discharged when the diet was well tolerated and no complications were detected. Perioperative complications were defined as unexpected and untoward events occurring either during the procedure or on the post-operative period.

Patients were evaluated 2 weeks after surgery and re-examined at 3-month intervals for the first 2 post-operative years and every 6 months thereafter. Clinical examination and rectoscopy were performed during each of the follow-up sessions.

Patients were referred to radical rectal resection whenever pathology specimen of the TEM showed rectal wall invasion; pT2, pT3 or high-risk T1 tumours; such as pT1 sm3, or lymphovascular invasion.

RESULTS

A total of 28 patients had a rectal polyp larger than 5 cm in size and underwent TEM during the study period. Table 1 summarises patients’ demographic data and tumours’ characteristics. The mean age was 66 years (range 42–83). Sex distribution was similar; 15 patients were male and 13 females. Most patients (n = 21) had an American Society of Anaesthesiology score of 1 or 2.

Table 1.

Patient demographics and clinical variables

Variable	Patients (n=28), n (%)
Age (years) (range)	66 (42-83)
Sex (male/female)	15/13
ASA score
1	13 (46)
2	9 (32)
3	6 (21)
Indication of surgery
VA LGD	6 (25)
TVA LGD	5 (21)
TVA HGD	4 (17)
TA LGD	4 (17)
TA HGD	5 (21)
Tumour diameter (cm) (range)	6.2 (5-8.5)
Distance from anal verge (cm) (range)	8.4 (5-13)
Rectal wall location
Posterior	10 (36)
Anterior	5 (18)
Right lateral	6 (21)
Left lateral	7 (25)

ASA: American Society of Anaesthesiology, VA: Villous adenoma, LGD: Low-grade dysplasia, TVA: Tubulovillous Adenoma, HGD: High-grade dysplasia, TA: Tubular adenoma

All initial biopsies from the rectal lesions were adenomas on pathology. The distribution of type of adenomas is detailed in Table 1, 15 patients had adenomas with low-grade dysplasia (LGD) and 13 patients had adenomas with high-grade dysplasia (HGD). The mean tumour diameter was 6.2 cm (range 5–8.5 cm); with a mean distance from the anal verge of 8.4 cm (range 5–13). Tumour location upon rectal wall varied among the patients; 10 patients had a lesion located in the posterior rectal wall, five patients in the anterior wall and 13 lesions were located in the lateral walls.

No major intraoperative or post-operative complications were recorded [Table 2]. In seven patients 109 min (range 80–135 min). In five patients, the peritoneal cavity was entered during full-thickness resection of the lesion. In four patients, an additional laparoscopy was required to visualise the suture line of the rectal wall and to perform an anastomotic leak test. For the remaining patient, trans-anal suture of the rectal wall was performed successfully. The additional laparoscopy added 25 min (range 20–35 min) to the total operating time.

Table 2.

Operative and perioperative course

Variable	Patients (n=28), n (%)
Changing patients’ position during TEM	7 (25)
Peritoneal entry	5 (18)
Laparoscopy	4 (14)
Operation time (min) (range)
TEM	109 (80-135)
Laparoscopy	25 (20-35)
Hospital length of stay (days) (range)	2 (1-4)
Perioperative complications (%)
Fever	1 (3.5)
Bleeding	1 (3.5)
Urinary retention	2 (7)
Pelvic sepsis	0
Peritonitis	0

TEM: Transanal endoscopic microsurgery

The median length of stay was 2 days (range 1–4). No major 30-day post-operative complication was noted. Urinary retention occurred in two patients and required a urinary catheter insertion; fever was noted in one patient and was attributed to atelectasis. Rectal bleeding occurred in one patient and was self-limiting; the patient was treated conservatively without the need for blood transfusion or any invasive intervention. No complications related to laparoscopy were noted.

Observing final pathology, surgical margins were involved in two specimens. These patients underwent additional surgery; one patient had LGD and underwent Re-TEM and the second patient had T2 adenocarcinoma in the final pathology with involved deep margins and underwent laparoscopic AR surgery. The final pathology of the specimens is detailed in Table 3. Adenocarcinoma was found in eight patients (T1 carcinoma in five patients and T2 in 3 patients), and the adenomatous polyp was found in 20 patients (LGD in nine patients and HGD in 11 patients). All five patients with T1 tumours had free surgical margins and were followed up without additional surgery. In three patients with T2 carcinomas, a completion of rectal resection was required. One patient had also involved surgical margins, and as mentioned before, he underwent LAR, the final pathology after LAR was T2N0. One patient underwent laparoscopic APR, and the final pathology revealed T2N0. The last patient, an 83-year-old woman, refused an additional surgery and was referred to radiation therapy.

Table 3.

Pathology results

Variable	Patients (n=28), n (%)
Involved specimen margins	2 (7)
Final pathology
Adenoma LGD	9 (32)
Adenoma HGD	11 (40)
Carcinoma T1	5 (18)
Carcinoma T2	3 (11)
Additional surgery
Re-TEM	3 (13)
Anterior resection	1 (4)
Abdominoperineal resection	1 (4)

LGD: Low-grade dysplasia, HGD: High-grade dysplasia, TEM: Transanal endoscopic microsurgery

Mean follow-up of 64 months (range 20–81 months). No long-term complications were noted. None of the patients reported incontinence or rectal stenosis. Local recurrence of the rectal tumour was detected in one female patient at 33 months after TEM. A 48-year-old female who had a 5 cm flat polyp posterior wall in the lower rectum, final pathology revealed a TVA HGD polyp with free margins. The patient developed a recurrence 26 months after the TEM. The patient underwent radiochemotherapy treatment, followed by laparoscopic APR. The final pathology was T3 without nodal involvement.

DISCUSSION

Minimally invasive colorectal surgical techniques such as TEM offer an effective treatment option with minimal morbidity. In the present study, TEM allowed for adequate complete macroscopic excision in all patients. All patients had a full-thickness excision and were excised in one specimen. All giant polyps have potential malignancy and need to have an R0 resection. Other studies examining TEM in the treatment of large and giant adenomas report full-thickness excision in 52%–100% of the cases.[16-18,20] Our results of 7.1% positive resection margins are lower compared with other studies on the subject, which report R1 resection in 9.7%–30.7% of patients. Only one patient (3.5%) in our study was diagnosed with a recurrence during the post-operative observation period. In the literature, the recurrence rate was 5.6%–25.6%, and the median time to recurrence was 10 (range 4–33) months.[16-18,20]

One of the most important factors in determining a patient’s candidacy for local excision is deciding the probability and risk of local recurrence. Risk of invasive carcinoma in colorectal adenomas assessed by size and site. Larger Rectal Polyps are likelier to have malignancy.[21] In our study, 8 (29%) patients resulted in T1 and T2 carcinoma, similar to the reported rates. Tumour size alone or in combination with submucosal invasion depth or tumour budding appeared to be a significant predictive factor for locoregional failure after TEM for T1 rectal cancer.[22]

Patients’ selection for TEM depends largely on various diagnostic modalities, such as trans-rectal ultrasound, computed tomography and magnetic resonance imaging.[23] Unfortunately, there are still some limitations to the pre-operative diagnosis of large rectal adenomas using these modalities, and in some reports, up to 26% of the adenomas resected by TEM were found, at the definitive pathological examination, to be invasive adenocarcinoma.[24] In our study, three patients had T2 tumours in their final pathology, and 2 of the patients who agreed to surgery had additional surgery. Completion of surgery has been demonstrated to be safe and returns oncological outcomes to that of primary radical TME surgery.[25,26] This effect is also seen in series where immediate reoperation is performed.[27] However, it is important to note that in patients with distal rectal lesions who need additional post-TEM radical resection, it is more likely to result in an APR rather than a low AR.[28,29] This is due to the more challenging nature of the procedure in these circumstances, secondary to scar formation.

Observing long-term results, no incontinence was reported among the patients. In accordance with published reports. Cataldo et al.[30] addressed this concern, looking at the ability to defer defecation, number of bowel movements per 24 h, Fecal Incontinence Severity Index and Fecal Incontinence Quality of Life survey. In their study, TEM did not have a significantly deleterious effect on fecal continence. In another study by Morino et al.,[31] it was observed that post-procedure anal resting pressure decreased temporarily but returned to pre-operative values at a mean of 4 months after surgery. No differences in maximum squeeze pressure or duration of voluntary contraction were noted.

None of the patients in our study suffered from post-operative rectal stenosis. Rectal stenosis following TEM excision is rare. Barker and Hill[32] reported a rate of 3.6% in their series, which occurred mainly in patients with circumferential rectal lesions. On the other hand, patients undergoing AR of rectum experience AR syndrome symptoms in 50%–90% of cases.[5]

One of the surgical challenges is rectal perforation and intraperitoneal entry during TEM. This challenge can occur in 9% of the patients and carries a risk of intra-abdominal complications.[33,34] In five patients, the peritoneal cavity was entered during full-thickness resection of the lesion. We routinely perform a laparoscopy when a rectal perforation with peritoneal entry occurs during TEM; this complication is more common in resection of large and upper rectal lesions. Securing the hand-sewn closure of the rectal defect during TEM by adding diagnostic laparoscopy and leak testing of the suture line area can be an important safety measure of good rectal wall closure.[35] This technique was implemented in four patients if our cohort.

Our study suffers from several limitations. First, it is limited by the retrospective nature of the study. Another limitation is the small sample size and the fact that this is only a single institution’s experience. Long accrual periods contribute to variability in perioperative care as it evolved over the years, and diagnostic modalities were not uniform for all patients.

CONCLUSION

TEM is an acceptable technique for the treatment of large polyps with minor complications and reasonable recurrence rates. Laparoscopy following peritoneal entry increases the ability to perform local excision with more safety. When salvage radical surgery is indicated, outcomes are satisfactory. TEM may be considered regardless of the size and the location of the rectal polyp.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.