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Transanal Endoscopic Resection for Rectal Tumour in BC
In the last two decades, a major advancement in rectal cancer surgery has been the adoption of total mesorectal excision (TME), involving the complete removal of the tumour (with negative margins) along with the complete lymphatic basin contained in the mesorectal envelope. Adhering to this principle has led to dramatic reductions in local recurrence.1-3 However, despite advances in our ability to perform low colorectal and coloanal anastomoses, a significant proportion of patients undergoing this procedure have functional problems with defecation, including incomplete evacuation, urgency, antidiarrheal dependence and fecal incontinence.
In an effort to reduce the morbidity of major rectal resection and low anastomoses, work has been done to develop transanal approaches to distal and small rectal cancers as an alternative to conventional abdominal surgery. In early rectal cancers, the risk of lymphatic involvement has been shown to be between 8 and 15%.4-6 Based on these data, local excision has been advocated by some for T1 and some T2 rectal lesions. However, this procedure can be technically difficult. Visualization of the tumour is limited and confidence in removal with the standard 1 cm circumferential margin can be compromised.
In 1984, Buess proposed a minimally invasive technique for transanal excision: transanal endoscopic microsurgery (TEM).7 In this technique, a 40mm operating proctoscope is inserted into the anus and held in place with an adjustable mount affixed to the operating table. This proctoscope forms an airtight seal with the anal canal and the rectumis insufflated with carbon dioxide. The proctoscope has three ports for instrument insertion and a fourth port for the camera (see diagram in Brown and Raval).8 Utilizing modified laparoscopic instruments that accommodate the smaller working space in the rectum, full thickness excision is more easily and reliably accomplished, as is a margin of normal tissue. While leaving small defects in the rectal wall below the peritoneal reflection is a safe and acceptable surgical approach, laparoscopic suturing techniques can be used to close the defect. TEM resection has been described for lesions up to 25cm away from the anal verge. Patients can often be sent home the same or next day. However, the procedure is time-consuming, sometimes difficult, and expensive.
The role of transanal excision by any method for T1 and T2 rectal cancer is controversial from an oncologic perspective. Several series in the last two decades have shown the recurrence rate to be anywhere from 0 to 33%. While no randomized, controlled trials have been performed comparing transanal and abdominal resection, the best evidence available comes from several recent cohort studies, which have shown inferior outcomes in local recurrence and overall survival with local excision. 9-11
The local recurrence rates after radical surgery for T1 rectal cancers in these studies mirror the less than 1% demonstrated in the Dutch Rectal Cancer trial in the surgery-only arm, while that after transanal excision is approximately 15-18%.
Most series of transanal excision use the conventional technique of anal retractors, hand-held instruments and electrocautery. This can be a challenging procedure to perform, even for the experienced surgeon. Thus, it is possible that some of the local recurrences cited are related to suboptimal surgical technique. In a recent systematic review of 31 studies evaluating TEM in patients with rectal cancer, the median local recurrence rate was 8.7% in patients with T1 cancers.12 While many of these studies were case series, the lone randomized trial in this review comparing TEM to radical surgery demonstrated a local recurrence rate of 4.1% (1/24) vs. 0% 0/26).13 A more recent randomized trial compared TEM and laparoscopic total mesorectal excision in patients with T2 rectal cancer undergoing preoperative chemoradiation (35 patients per arm, 84-month median follow up). The authors showed no significant differences in local recurrence (5.7% TEM vs. 2.8% laparoscopic), distant metastases (2.8% in both), or survival (94% in both).14 These data suggest that the TEM technique may be better at achieving local control than convention transanal excision.
While TEM may be better than conventional local excision for T1 rectal cancers, neither has been established as equivalent to radical resection.
Nonetheless, transanal strategies for T1 rectal cancers have not been abandoned. In some elderly patients with multiple comorbidities and high operative risk, increased local recurrence rates may be acceptable in order to avoid the morbidity of major abdominal surgery. While there is limited data on quality of life outcomes, Doornebosch et al. demonstrated significantly more problems with defecation after TME when compared to patients treated by TEM.15 Subclassification of T1 cancers based on depth of submucosal invasion suggests that there are subgroups of patients who can expect local recurrence rates comparable to those seen after radical surgery.16 Furthermore, there is some evidence that subsequent salvage by radical resection is possible in nearly 80% of patients with local recurrence after local resection.10 With aggressive surgical excision of both local and distant recurrent disease, Weiser et al. demonstrated five year disease specific survival of 53%.17 Finally, the role of neoadjuvant or adjuvant chemoradiation plus TEM has yet to be established (early results are encouraging), and trials are currently recruiting patients to help determine the role of pre or post-operative therapy.
The colorectal surgeons at St. Paul's Hospital in Vancouver (Dr. Terry Phang, Dr. Carl Brown, Dr. Manoj Raval) have recently acquired the TEM technology to offer this procedure to British Columbians. Since March 2007 we have operated on 42 patients, with the indication for operation as follows: 17 adenocarcinoma, 20 adenoma, 3 carcinoid, and 1 other. Patients have ranged in age from 39 to 95. Tumours varied in height from 2 to 12 cm above the anal verge and in size from 1.5 to 12 cm. Nine patients received chemoradiation (3 preop, 6 postop). Twenty of 42 patients had closure of the defect, with the remainder being left open. In 39/42 patients, a margin of 1cm or greater was obtained, and in 38/42 patients a full-thickness resection including mesorectal fat was performed (we obtained lymph nodes from 2 of these specimens). Four patients who had postoperative abdominal pain and were found to have intrabdominal or retroperitoneal free air on CT scan, though all were successfully treated nonoperatively with bowel rest and IV antibiotics (all patients underwent full bowel preparation). Two patients developed postoperative bleeding, neither of which required return to the operating room for control. Patients without complications were sent home the same or next day. We have had no recurrences in patients who underwent R0 resections, although our followup is short (maximum 21 months). We are currently performing a study to compare the pre- and postoperative rectal function in patients undergoing TEM.
Generally, our indications for using the TEM procedure have been rectal adenomas not amenable to endoscopic resection and rectal cancers in patients with major comorbidities who are at prohibitive risk to undergo a major transabdominal resection. To date, we have limited TEM resection to tumours in the extraperitoneal rectum, although full-thickness excision of tumours up to
25 cm have been described, with laparoscopic closure of the intraperitoneal colon.
In conclusion, transanal resection of rectal cancers, while not oncologically equivalent to radical resection, has a place in patients who would not tolerate abdominal resection well due to comorbidities, in patients where the diagnosis is in question, or where patients would prefer such an approach (provided they understand the oncological implications). Recent evidence suggests that TEM may be superior to conventional, "open" transanal resection from an oncologic perspective, and may be the procedure of choice in these patients. Neoadjuvant chemoradiation may play a role in further improving oncologic results.
References:
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2. Martling AL, Holm T, Rutqvist LE, et al. Effect of a surgical training programme on outcome of rectal cancer in the County of Stockholm. Stockholm Colorectal Cancer Study Group, Basingstoke Bowel Cancer Research Project. Lancet 2000;356:93-6.
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14. Lezoche G, Baldarelli M, Guerrieri M et al. A prospective randomized study with a 5-year minimum followup evaluation of transanal endoscope microsurgery versus laparoscopic total mesorectal excision after neoadjuvant therapy. Surg Endosc 2008;22:352-8.
15. Doornebosch PG, Tollenaar RA, Gosselink MP et al. Quality of life after transanal endoscopic microsurgery and total mesorectal excision in early rectal cancer. Colorectal Dis 2007;9:553-8.
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