Background
Transanal endoscopic microsurgery (TEM) offers several advantages over conventional transanal excision. It provides better exposure and visualization than standard transanal excision and affords access to lesions higher in the rectum. It is associated with less morbidity and quicker recovery time than a radical transabdominal approach. The major limitations of TEM have been that it requires expensive, highly specialized equipment and has a steep learning curve. [1] Accordingly, it should be performed only by skilled and experienced surgeons.
Transanal minimally invasive surgery (TAMIS) was developed to address some of the issues encountered with TEM. [2] It offers several benefits over TEM: It requires minimal setup time, and the use of existing laparoscopic cameras and instruments offers a lower-cost alternative to TEM. Nonetheless, the learning curve appears to be generally comparable.
A comparison of patients who underwent TEM (n = 53) or TAMIS (n = 68) for resection of intraluminal rectal tumors showed that although median operating time was significantly shorter for TAMIS (45 vs 65 min), blood loss was negligible in both groups. [3] Resection margins, lesion grade, and invasion depth were comparable for the two approaches; however, the postoperative readmission rate was significantly higher in the TEM group (17% vs 4.4%).
Robotic TAMIS (R-TAMIS) has been proposed as a potential alternative to both TEM and standard TAMIS. [4] In a case series by Schwab et al, [5] the three techniques were compared, and R-TAMIS tended to be faster than TEM and TAMIS and to be more likely to result in negative surgical margins.
Indications
TEM can be used as a curative operation for rectal polyps that are not amenable to colonoscopic resection. [6] In addition, it may be used in selected patients with rectal cancer. [7, 8] The following indications have been recommended by various surgical societies, including the American Society of Colon and Rectal Surgeons (ASCRS):
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Lesions smaller than 3 cm; however, a study by Khoury et al reported the use of TEM to treat benign rectal lesions in the range of 5-8 cm [9]
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Mobile lesions
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Polypoid lesions
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Anatomically accessible lesions localized to the bowel wall (T1N0)
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Lesions confined to the extraperitoneal region of the rectum
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Lesions occupying less than 40% of the circumference of the bowel lumen; however, the use of TEM for giant circumferential rectal adenomas has been reported [10]
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Well-differentiated or moderately differentiated lesions [11]
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Lesions not associated with lymphovascular invasion
Management of rectovaginal fistulas and anastomotic dehiscence management by means of TEM has also been reported. [12]
TEM has become an accepted procedure for benign adenomas [13, 14, 15, 16, 17, 18, 19] and potentially for early carcinomas of the rectum. [20, 21] Low recurrence rates have been reported for adenomas treated with TEM. [14, 16, 17, 22, 23]
Definitive treatment of T2 or T3 rectal lesions with TEM has not been recommended. However, a study by González et al, which examined surgical and long-term oncologic outcomes of TEM for treatment of T2-3 rectal cancer after chemoradiotherapy and complete clinical response, found TEM to be oncologically safe and effective in this setting. [24] The use of TEM as palliative surgery for advanced rectal lesions is also acceptable for patients with comorbid conditions and disseminated disease who are otherwise unfit for more radical surgery. [25, 26]
In a meta-analysis comparing TEM with endoscopic submucosal dissection (ESD) for the treatment of rectal tumors, the two procedures were found to be similar with regard to the rates of resection, adverse events, and recurrence; however, both the procedure time and the duration of hospitalization were shorter with ESD. [27] An international collaborative study by Kim et al found ESD to be safer and more cost-effective than TEM for the treatment of early rectal cancer. [28]
An approach that combines TEM with ESD (TEM-ESD) has been described. [29]
TEM under fluoroscopic-endoscopic guidance was reported to manage anastomotic site stricture in a patient who had undergone a modified Duhamel operation for Hirschsprung disease, which was treated by creation of a neoanastomosis. [30]
Contraindications
Contraindications for TEM include the following:
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Positive lymph nodes
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Distant metastasis
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Ulcerated tumor
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Poorly differentiated tumor
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Lymphovascular invasion
Technical Considerations
Procedural planning
Patient selection is the key consideration, and strict criteria are defined for appropriate candidates.
Preoperative clinical evaluation and histologic grading of rectal lesions often prove inaccurate in assessing the staging and local spread. [32] The use of preoperative endoluminal ultrasonography (US), [33] pelvic magnetic resonance imaging (MRI), [34, 35] or both is imperative to ensure the most accurate assessment of tumor depth and nodal status.
In a study comparing transrectal US (TRUS) with MRI for preoperative evaluation of patients with rectal villous adenoma treated with TEM, Raynaud et al suggested that TRUS was preferable for this purpose, noting that MRI overstaged lesions in 54% of patients. [36]
In a study of 12 patients who underwent TEM where endoscopic US (EUS) was used in the preoperative staging of early rectal cancer, EUS was found to be accurate in determining the T stage in 90.8% of cases and the N stage in 76.7%, as confirmed histopathologically. [37]
Despite advances in clinical staging, as many as 15% of tumors may be staged inaccurately.
Complication prevention
Standard preoperative preparation is required to prevent complications. Optimizing medical status for anesthesia, when indicated, is important. In addition, prophylaxis for deep vein thrombosis (DVT), bowel preparation or preoperative rectal irrigation, and preoperative antibiotic prophylaxis are provided. A Foley catheter is placed after induction of anesthesia.
Preoperative nutritional status may be the most significant predictor of outcomes. Every effort should be made to assess the patient's nutritional status and to improve it if needed.
Outcomes
Winde et al conducted a prospective study and found that the operating time, blood loss, length of hospital stay, and analgesic requirement associated with TEM were significantly less than those associated with abdominal resection. [38] The recurrence rates of tumors following TEM have been reported to range from 2.4% to 16%, [14, 16, 17, 18, 31, 39, 40] whereas the recurrences rates associated with conventional anal excision have been in the range of 4-36%. [41, 42, 43]
In a systematic review and meta-analysis of local resection or TEM versus radical resection in stage I rectal cancer, Veereman et al found that for primary outcomes (overall survival, disease-free survival, local recurrence-free survival, and metastasis-free survival), no evidence could be found for the superiority of local or radical resection. [44] For secondary outcomes (blood loss, hospital stay, operating time, number of permanent stomas, and perioperative deaths), the evidence favored local resection.
There is a need for additional randomized studies comparing TEM with traditional local excision and radical resection.
In a multicentric trial aimed at assessing long-term oncologic outcome and health-related quality of life (QoL) in patients with cT1-3N0M0 rectal cancer who underwent neoadjuvant chemoradiotherapy (CRT) followed by TEM, Stijns et al reported a 7.7% 5-year recurrence rate, an 81.6% 5-year disease-free rate, and an 82.8% overall survival rate. [45] Two thirds of the patient had good long-term oncologic outcome and health-related QoL, with some amount of bowel dysfunction.
TAMIS offers several benefits over TEM. It requires minimal setup time, and its use of existing laparoscopic cameras and instruments is associated with lower cost. Nonetheless, the learning curve is generally comparable, though it may be shorter for laparoscopic surgeons already proficient with single-port approaches. [46] In the hands of experienced laparoscopic surgeons, TAMIS also provides magnified visualization of tumors by the rectosigmoid junction. [47] Thus, it is cost-effective, [48] innovative, safe, and feasible in carefully selected patients. [49] More comparative studies and randomized trials are required to establish its efficacy with respect to cancer recurrence rates and overall survival. [50]
