While the standard treatment modality for low-grade rectal cancer is transabdominal perineal resection (APR), several new techniques have emerged in recent years to treat low-grade rectal cancer. In an article in World J Gastrointest Oncol, Dimitriou, MD, Greece, summarizes the indications, technical approach, and oncologic and functional outcomes of the new treatment techniques, emphasizing that treatment according to guidelines and patient characteristics will ensure maximum patient benefit.
Low-grade rectal cancer is defined as a tumor < 5 cm from the anal verge. The most fundamental advancement in rectal cancer surgery in the last 20 years or so has been total mesorectal excision (TME), introduced by Dr. Heald in 1982, which has never been compared prospectively with conventional surgical approaches, but has clearly demonstrated advantages in control of local recurrence and survival compared to historical controls.
The standardized TME has a recurrence rate of < 10% and 5-year survival of 80%. The Dutch TME trial confirmed these results and clearly demonstrated an increased risk of local recurrence if patients underwent incomplete rectal mesenteric resection.
Laparoscopy provides better visualization of the pelvis and facilitates rectal resection. Although laparoscopic TME is a standardized and reproducible procedure, it is still technically complex. the rate of positive circumferential margins (CRM) after laparoscopic anterior resection was very high in the UK MRC CLASICC trial, and the location of the tumor in the mid-distal rectum was an important risk for a positive CRM. Patients with positive CRM (<1 mm) have an increased risk of local recurrence and distant metastasis and reduced overall survival, and the TME technique may reduce the rate of positive CRM.
Another change in the surgical treatment of rectal cancer is the re-evaluation of the distal dissection margin (DRM) length, usually to ensure a 2 cm length. Because intra-distal bowel wall propagation or backward lymph node invasion is rare, and because recent review studies have shown no negative impact on local recurrence or overall survival in low-risk tumors when the DRM is <1 cm or even <5 mm, the TME technique allows for a shorter DRM and the circumferential anastomosis significantly reduces the transabdominal perineal resection rate.
A meta-analysis showed that patients treated with APR had a positive CRMs rate of 10%, a local recurrence rate of 20%, and a 5-year survival rate of 59%, whereas patients treated with LAR (low anterior rectal resection) had a positive CRMs rate of 5%, a local recurrence rate of 11%, and a 5-year survival rate of 70%, and the oncologic outcome after APR was not superior to that of LAR, and the worse outcome with APR may be due to defects in the surgical technique itself The worse outcome of APR may be caused by the defect of the surgical technique itself or the characteristics of the tumor itself.
In recent years, several new techniques have emerged for the treatment of very low rectal cancer with the aim of preserving the continuity of the GI (gastrointestinal tract) and improving oncologic outcomes and functional outcomes. This article will describe these new techniques and the data supporting improved oncologic and functional outcomes.
Intersphincteric resection (ISR)
Patient Selection
Patient selection is based on MRI, CT, endoanal ultrasound, rigid rectoscopy, and fingerprick findings. In particular, the examination under anesthesia is important to assess the tumor activity, the relationship between the tumor and the perianal sphincter, and the final decision on the surgical procedure. A recent review suggests that ISR should be used for T1-3 tumors within 30-35 mm of the anal verge, with or without invasion of the internal anal sphincter (IAS).
Absolute contraindications to ISR are T4 tumors, extra-anal spreaders (EAS) invasion, fixed tumors on finger palpation, poorly differentiated tumors, poor preoperative spreaders function, distant metastases, and the presence of psychiatric disease.
Surgical technique
ISR, first proposed by Dr. Schiessel in 1994, involves resection along the anatomic plane between the IAS and EAS, with the aim of increasing the retention of the dilator muscle and avoiding a permanent stoma in low-grade rectal cancer.
The procedure consists of two parts: abdominal and perineal. The abdominal procedure begins with separation of the peritoneum over the inferior mesenteric vessels, separation of the left colonic mesentery from the fascia, and exposure of the left colonic artery followed immediately by high ligation of the inferior mesenteric vein and inferior artery. After ligation of the vessels, the peritoneal folds around the sigmoid colon and rectum were separated, the sigmoid mesentery, rectal mesentery and fascia were separated, and resection continued along the rectal mesenteric plane. Sometimes it is also necessary to free the splenic flexure of the colon.
After separation of the mesenteric fascia, the left colonic mesentery, sigmoid mesentery and rectal mesentery are removed and the fascial integrity of the specimen is removed, as well as the lymph nodes to the greatest extent possible. Laparoscopic, open and robotic resections are all available for abdominal resections.
Perineal resection requires the patient to be placed in a high lithotomy position with a self-fixing puller to expose the perineum. 1 mg of epinephrine dissolved in 20 mL of saline is injected at multiple points into the submucosa of the anus to reduce bleeding and facilitate interdigital resection. A circumferential incision of the anal mucosa is made at least 1 cm distal to the T1 tumor and 2 cm to the T2-3 tumor to allow resection of the entire rectal wall and part/all of the IAS. purse-string sutures are used to close the anus to prevent trans-perineal dissemination of tumor cells.
The trans-perineal portion of the intersphincteric resection, A: Akagi et al; B: Saito et al, is continued under direct vision along the intersphincteric space towards the cephalic end to meet the abdominal TME plane, and the specimen is usually removed transanally. A recto-anal anastomosis is then performed to restore GI continuity. There are various types of anastomoses such as J-pouch, T-pouch or direct coloanal anastomosis, the choice of which is largely based on the surgeon’s personal preference. Finally, a rerouted colostomy or ileostomy is performed.
There are three types of ISR: partial, subtotal and total, differentiated by the extent of IAS resection. Partial ISR is resection of the upper third of the IAS, subtotal ISR is resection of two-thirds of the IAS, and total ISR is complete resection of the IAS. combined resection of the EAS is sometimes used when the tumor may have invaded the intersphincteric or external dilator muscle. ISR differs from traditional colorectal anastomosis after super-low anterior resection because ISR is characterized by resection of the internal dilator muscle along the intersphincteric plane.
Early postoperative outcomes
Surgical mortality fluctuates from 0%-1.7% and postoperative complications range from 8%-64%. The major causes of complications are anastomotic leak, anastomotic stricture, fistula formation, pelvic abscess, incisional complications, bleeding, and intestinal obstruction. Anastomotic leak is associated with postoperative anastomotic stricture, cancer recurrence, poor postoperative function, and increased operative mortality.
A meta-analysis showed a cumulative complication rate of 25.8%, an anastomotic leak rate of 9.1%, and a pelvic abscess rate of 2.4%. Akagi et al. reported a 12% complication rate for Dindo grade II and a 5.6% anastomotic leak rate, while Saito reported a 10% anastomotic leak rate.
Oncologic results
Tilney and Tekkis identified oncologic outcomes after ISR through a literature search, with 9.5% local recurrence, 81.5% mean 5-year survival, and 9.3% distant metastases. Martin et al. reported that negative distal margins required a mean of 17.1 mm, 96% of patients had a negative CRM margin, and 97% had R0 resection; with a median follow-up of 56 months, total local recurrence was 6.7%, 5-year disease-free survival was 78.6%, and 5-year overall survival was 86.3%.
A large prospective study enrolling 124 patients with low-grade rectal T1-3 tumors without preoperative chemoradiotherapy (CRT) was published in 2013. The results showed an overall postoperative recurrence rate of 16.1%, local recurrence of 4.8%, lateral lymph node metastases of 2.4%, pelvic floor recurrence in 2.4% of patients, and distant metastases of 10.5%; comparing the oncologic results of contemporaneous ISR and APR, the overall recurrence-free survival and local recurrence rates after ISR were similar to those of APR.
In Saito’s prospective study, 199 patients were recruited and treated with ISR, 25% received neoadjuvant CRT, and 20.6% underwent concomitant EAS resection. At a median follow-up of 6.5 years, 14.1% had lung metastases, 13.6% had local recurrence with or without distant metastases, 7.5% had liver metastases, and 4.5% had multiple recurrences. Positive CRM was 19.6%, with expected 7-year overall survival, disease-free survival and local recurrence-free survival of 78%, 67% and 80%, respectively. However, T4 tumors were included in this study.
Most studies comparing LAR, APR and ISR concluded that oncologic outcomes were not significantly different, except for Saito, who reported worse 5-year overall survival for APR than for ISR. 77, 68 and 33 patients were in the ISR, LAR and APR groups, respectively, with no significant differences in overall recurrence, local recurrence and 5-year local recurrence-free survival between the groups. 76.4% 5-year overall survival in the ISR group was better than 51.2% in the APR group and similar to 80.7% in the LAR group. This may be related to the fact that there were more patients in the APR group with progressive disease.
According to TNM staging, the 5-year overall survival was 90.0%, 79.8% and 65.6% for stage I, II and III patients in the ISR group, respectively; the 5-year overall survival for stage III patients in the ISR, LAR and APR groups was predicted to be 65.6%, 56.3% and 33.3%. These long-term results suggest that the oncologic outcomes of ISR are very good. However, T3 tumors and margin-positive patients are more likely to experience local recurrence after ISR.
CRM was a very strong predictor of local recurrence, with positive CRM patients having significantly worse overall survival, disease-free survival, and local recurrence-free survival than CRM-negative patients. Other factors contributing to local recurrence included undifferentiated tumors, preoperative CA199 above 37 U/mL, and pathologically poorly differentiated tumors with N1 or N2 lymph nodes.
Functional outcome: quality of life
Postoperative anal function is an important marker of clinical outcome in dilator preserving surgery for low rectal cancer, but only a few studies have reported short-term postoperative outcomes. resting anal pressure does not fully recover rapidly after ISR and needs to be gradually restored; maximum squeeze pressure is not affected. In conclusion, anal function needs to improve gradually over time.
Khler et al. reported a 29% reduction in resting anal pressure after ISR, with squeeze pressure returning to preoperative levels 12 months after surgery; Martin reported an average of 2.7 bowel movements per day, with nearly half of patients having normal bowel movements, 1/3 having fecal incontinence, 23.8% having gas incontinence, and 18.6% having urgency; Denost et al. reported half of patients functioning well, 39% having mild fecal incontinence, and 11% having severe fecal incontinence. Saito et al.
Saito et al. reported long-term functional outcomes in 199 patients with a bowel movement of 4.0±3.7/day and a median Wexner score of 8.5 at 5 years after fistula closure, with approximately 50% having fecal interruption, gas incontinence, 30% having fecal incontinence, and ¼ having difficulty emptying. In men, preoperative CRT was a predictor of poor bowel control, and type of surgery did not affect long-term functional outcomes. the Ito report also supports that preoperative CRT has the greatest impact on anal function, while the Yamada study showed that patient age at the time of surgery was the only postoperative risk factor for fecal incontinence.
Denost et al. reported that risk factors for fecal incontinence after ISR were directly related to tumor level and anastomotic height, and that to obtain good bowel control, the tumor needed to be more than 1 cm from the anorectal ring and the anastomosis more than 2 cm from the anal verge.
A recent study comparing functional outcomes after ISR and LAR found that postoperative defecation function such as frequency of defecation, presence of urgency, differentiation of venting and perianal skin itching was similar in both groups, with lower Wexner scores in the LAR group, but no difference in fecal incontinence quality of life scores (FIQL) between the two groups.
Bretagnol et al. used the SF-36 and FIQL questionnaires to compare quality of life (QoL) in patients with ISR and conventional colorectal anastomosis and did not find differences in physical and mental scores between the two groups. saito et al. reported that patients with ISR with or without EAS resection were in better or equal status at 5 years, whereas patients with preoperative CRT showed a significant decrease in FIQL quality of life scores at long-term follow-up.
Conclusions
ISR is an alternative to the classic surgical approach for the treatment of low-grade rectal cancer. The literature shows that ISR is indicated for T1-3 tumors, located 30-35 mm within the anal verge, with or without IAS invasion, with comparable oncologic outcomes to LAP and APR, and acceptable quality of life.APR can be used for locally progressive tumors.
Anterior Perineal Ultra-Low Anterior Rectal Resection (APPEAR)
Patient selection
Pre-perineal ultra-low anterior rectal resection is used to preserve the anal meatus during resection of benign and malignant rectal tumors that previously required conventional surgical treatment such as APR or total proctocolectomy. Recent cases have reported APPEAR for low rectal cancer 2-5 cm from the anal verge.
Surgical technique
The APPEAR technique, first proposed by Dr. Williams in 2008, includes both abdominal and perineal components and allows access to the low rectum between the levator muscle and the superior border of the EAS, which is more difficult to access. The abdominal procedure is consistent with the abdominal procedure in ISR and can be performed either open or laparoscopically.
The perineal procedure requires the patient to be placed in a high lithotomy position with 1/300,000 epinephrine solution in the rectovaginal/prostate plane and a crescentic incision in the skin between the base of the vagina/scrotum and the anal verge in the midline of the perineum. The skin and subcutaneous tissue at the external anal dilator and transverse perineal muscles are separated and folded back upwards. In female patients, the perineal body is accessed through the plane between the posterior vaginal wall and the anterior rectal wall.
In male patients, access is via the recto-urethral/prostate plane, with the bilateral recto-urethral muscles close to the rectum being freed at entry, followed by sharp/blunt separation of the anterior rectal wall from the prostate, with care being taken to avoid damage to the neurovascular bundle when separating the inferior aspect of the prostate from the rectum due to its close proximity to the rectum. The separation is continued cephalad to the level reached by the abdominal surgeon. The rectum is then freed laterally and the specimen is removed via the perineum. A direct colorectal anastomosis or colonic pouch establishes GI continuity and protects the ileostomy.
Early postoperative results
The main postoperative complication was perineal incision infection with an incidence of 15.4%-60%, and in some patients, perineal fistulae of the colonic/ileal pouch. Anastomotic stricture was reported in 3 patients in the early study.
Oncologic outcomes
Only two studies have addressed oncologic outcomes, including one study in which only half of the patients had rectal cancer with a median DRM of 20 mm and a median CRM of 5 mm, with no local recurrence and one case of raw distant metastasis at 2 years of follow-up. No recurrence was also found in a recent study, but the median follow-up was only 11 months.
Functional outcome: QoL
Only two studies have addressed functional outcomes. One early study showed a median Wexner score of 5 in patients with colorectal anastomosis after ileostomy closure, and all patients had bowel control, with only one patient having fecal incontinence and one case of urgency. In another study, the mean Wexner score after stoma closure was 5.5. Both articles showed normal anal resting and squeezing pressures in patients after APPEAR. Only one study involved QoL and there was no significant change.
Summary
The APPEAR technique provides better distal access to the rectum for freeing than the ISR technique without damaging the dilator muscle. However, there is a high rate of complications, mainly perineal incisional infections, but fewer reports on oncological and functional outcomes are available and more studies are needed to evaluate this technique.
Local resection techniques: transanal endoscopic microsurgery and transanal minimally invasive surgery
Patient selection
Both approaches are primarily used for local transanal resection of low- and intermediate-grade benign rectal tumors. The literature suggests that transanal endoscopic microsurgery (TEM) can be used to remove benign rectal and extrarectal masses such as neuroendocrine tumors, retrorectal cysts, anorectal-vaginal septal masses, and to repair high rectovaginal fistulas, but there is limited experience with treatment of rare indications.TEM can also be used to treat anastomotic strictures, rectal prolapse, high external dilator fistulas, and pelvic drainage via the rectum.
The current indications for local excision have been expanded to include curative treatment of early-stage rectal cancer or palliative treatment, the latter of which primarily includes patients who refuse radical resection or who are not suitable candidates for surgery for progressive rectal cancer. Endoscopic polypectomy of occasionally detected cancers is an indication for local excision, especially in the case of clot-free polyps or when there is a particular concern about whether the margins are positive.
The use of transanal minimally invasive surgery (TAMIS) goes beyond local excision to include repair of rectourethral fistulas, distal rectal freeing, rectal foreign bodies, and most importantly, transanal TME using TAMIS.
The question remains as to which patients will benefit from TAMIS for early rectal cancer, and endorectal ultrasound (ERUS) and/pelvic MRI are required for preoperative staging; ERUS is more sensitive to determine the presence of deep bowel wall invasion, while MRI is superior for assessing rectal mesenteric lymph nodes and CRM.
Based on the image results, the NCCN guidelines clearly recommend that as a treatment option, the tumor should have the following characteristics: (1) movable and non-fixed; (2) less than 3 cm; (3) involving less than 1/3 of the peri-intestinal margin; (4) not exceeding the submucosa (T1), (5) moderately to highly differentiated; and (6) low risk histopathological features. On the other hand local resection should be avoided for lymphovascular invasion, perineural invasion and high-risk tumors with a mucinous component.
Surgical technique
TEM was first proposed by Dr. Buess in 1980, mainly for the removal of non-tipped rectal polyps that could not be resected endoscopically. The authors also invented the surgical proctoscope and tools to facilitate the application of this new rectal surgical technique and to ensure precision due to the use of binoculars and 3D viewing.
The equipment includes a rigid proctoscope that can be fixed to the operating table, carbon dioxide compression, suction, and rectal pressure monitoring devices. The proctoscope has a diameter of 4 cm and is available in adjustable lengths of 12 cm and 20 cm, making it necessary to know the position of the damage in the rectum at the time of application. The removable panel of the proctoscope allows for easy insertion of long instruments, easy aspiration, and with the stereoscope the physician can see damage up to 6 times larger. Recently, some physicians have also preferred to link the device to laparoscopic video.
For anterior compromise, the patient should be in the prone position and for posterior compromise, the patient should be in the lithotomy position. Rectal inflation should be maintained at 10-12 mmHg to ensure that the rectal wall is distended and the tumor is exposed. A monopolar electric knife is used to free the tumor starting 10-15 mm from the tumor margin. For adenomas located in the perineal portion of the rectum, mucosal resection should be performed carefully to avoid entry into the abdominal cavity.
For extraperitoneal adenomas and all invasive carcinomas, the standard treatment should be total resection. Total resection followed by caudal anastomosis should also be performed for perirectal adenomas in the middle and lower rectum. Invasive cancers located in the lateral and posterior walls may be resected with some perirectal fat and 1 or 2 adjacent lymph nodes to check for metastases.
Local resection of low-risk perforations by TEM is possible and requires either a tumor in the posterior quarter of the bowel wall with the perforation 18-20 cm from the tumor or a tumor in the anterior or lateral wall with the perforation 15 cm from the tumor; tumors at the anal verge are not suitable. The resection bed is usually closed with 3-0 polydioxanone sutures and must be closed if it enters the peritoneal cavity, whereas it can be closed without sutures if the resection bed is below the peritoneal retrusion. The surgical specimen should be marked and positioned for pathologic evaluation of the margins.
TEM has not been accepted by all colorectal surgeons, mainly because of the high cost of the device and the steep learning curve. These drawbacks have encouraged surgeons to try other transanal procedures.
TAMIS emerged in 2009 and uses a multi-channel transanal single fixation, combined with common laparoscopic instruments such as laparoscopic cameras and standard laparoscopic carbon dioxide compression, for both intracavitary and extracavitary procedures. A review study showed a total of 8 TAMIS platforms for local resection of rectal tumors. Regardless of the platform, the principles of TAMIS are consistent, with the most obvious advantage being fixability.
Early postoperative outcomes
Few deaths have been reported in the literature, with deaths mainly related to tumor metastasis or palliative treatment of progressive disease with TEM. Overall complications fluctuate from 6 to 31%, with a balanced distribution of benign and malignant tumors. Perioperative complications include bleeding and intraperineal perforation, the latter requiring open surgery. Postoperative bleeding ranges from 1-13% and mostly resolves spontaneously or requires blood transfusion. Approximately 5% of patients require reoperative management.
The results of TAMIS, a relatively new technique, are mainly based on retrospective studies and case reports. 6% of patients had positive microscopic margins and a 4% recurrence rate at 6 and 18 months, as reported by Albert et al. Intraoperative complications were 8%, postoperative comorbidities were 19%, and only 1 patient required reintervention.
A review study of TAMIS resections showed an average damage size of 3 cm, an average distance from the anal verge of 7.6 cm, an overall margin positivity rate of 4.36%, a tumor incompleteness rate of 4.1%, and an overall complication rate of 7.4%.
Oncological findings
The goal of T1N0M0 rectal cancer treatment is to maximize oncologic outcomes and minimize the long-term impact on QoL. Long-term oncologic outcomes of conventional transanal local excision of T1 tumors show local recurrence rates higher than 29%. The oncologic outcomes of TEM remain controversial, with some studies showing local recurrence rates of less than 10%, while some studies confirming that local recurrence rates with TEM are lower but not significantly different from those with transanal local excision, and studies suggesting that local recurrence rates with TEM for T1 rectal cancer can be as high as 20.5%.
Tytherleigh and Bach showed that the depth of submucosal invasion was the main factor for recurrence, with sm1 recurrence rates being low and sm2-3 recurrence rates similar to those of T2. Local excision of pT1sm1, without lymphovascular invasion, with tumors less than 3 cm in diameter had a recurrence rate of less than 5%, and local excision of pT1sm2-3 had a recurrence rate of up to 20%, similar to that of T2. In addition to sm depth of invasion, tumor differentiation, vascular/perineural invasion, positive margins, lymphocytic infiltration, lymph node metastasis, and tumor outgrowth are all poor factors for local recurrence.
According to NCCN guidelines, the standard of care for T2N0M0 rectal adenocarcinoma is TME without adjuvant therapy, as the incidence of lymph node invasion in these tumors is 12-29%. For T2 tumors, simple local excision, local excision followed by postoperative CRT, and preoperative CRT followed by local excision are all being tried. TEM alone is not suitable for T2 or more deeply invasive rectal cancers; CRT after local excision has been disappointing, with a 45% local recurrence rate; neoadjuvant CRT followed by TEM after downstaging has proven to be more promising.
In Lezoche’s prospective study, 70 patients with T2N0 rectal cancer underwent TEM or CRT followed by laparoscopic radical resection. the length of stay, blood loss, and duration of surgery were better in the TEM group than in the radical resection group, and there was no significant difference in the incidence of comorbidities between the two groups. oncologic outcomes such as local recurrence, distant recurrence, overall recurrence, and likelihood of disease-free survival did not differ between TEM and radical resection. These results suggest that TEM is acceptable for patients with elective T2 and no lymph node invasion or distant metastases.
A review by Borschitz showed that local resection of T2-3 rectal tumors after neoadjuvant CRT resulted in complete pathologic remission ypT0 with 0% local recurrence and 4% systemic recurrence; ypT1 with 2% local recurrence and 7% systemic recurrence; ypT2 with 7% recurrence both locally and systemically; and in the absence of pathologic response, i.e., ypT3, 21% local recurrence and 12% systemic recurrence.
A prospective study included 27 patients with lower rectal cancer treated with TEM after neoadjuvant CRT, ypT0-2, with a median follow-up of 15 months and a local recurrence rate of 15%. Lymphovascular invasion was an independent adverse factor for local recurrence, while tumor size, ypT status, T-decrease stage, lateral/radiographic margins, and degree of tumor regression were not significantly affected.
A review study comparing TEM with radical surgery for T1-2 rectal tumors concluded that TEM had a higher rate of local recurrence, but there were no statistically significant differences in overall mortality, overall survival, or risk of distant metastasis. There was bias in this study, such as no difference in recruitment of low-risk T1, high-risk T1, and T2 tumors.
Functional outcome
Prolonged proctoscopy and surgery can distend the anal canal and damage the anal dilation muscles, leading to postoperative fecal incontinence. It has been shown that the reduction in anorectal pressure in patients treated with TEM is directly related to the duration of the operation, but does not change control scores or other anorectal parameters.
In the prospective Cataldo study, which included 41 patients, there was no increase in bowel control after TEM, and no significant differences were found in mean preoperative and postoperative incontinence severity scores, FIQL scores, number of bowel movements per day, or ability to delay bowel movements.
A recent study found significant improvements in FISI and FIQL scores after TEM. Patients themselves reported improved QoL after surgery, and this improvement may be attributed to rectal damage and excessive mucus production leading to fecal incontinence, which disappeared after removal of the damage. Furthermore, larger rectal tumors consistently induce an internal anal dilator reflex, reducing anorectal function.
In a 5-year study of functional outcomes and QoL parameters by Allaix et al, as in previous studies, pressure parameters such as anal resting pressure, rectal sensitivity, maximum tolerated volume, and fecal incontinence limits decreased at 3 months postoperatively and returned to preoperative levels at 12 months postoperatively. Anal squeeze pressure did not change significantly compared to preoperative levels, and Wexner incontinence scores and QoL scores increased in the early postoperative period and returned to preoperative levels at 5 years.
Only one study involving functional outcomes after TAMIS removal of rectal polyps showed good short-term outcomes, with no significant change in functional outcomes compared to facility-assisted TEM surgery.
In summary
Both TEM and TAMIS are safe, TEM should be used for T1, pathologically well characterized rectal cancer, neoadjuvant CRT before TEM remains controversial, anal function improves after TEM, and for TAMIS there are not yet adequate oncologic and functional outcomes.
Transanal total rectal mesenteric resection
Patient selection
Transanal total mesorectal excision (TaTME) has been used primarily to overcome the technical challenges encountered in laparoscopic TME. Most physicians consider this technique appropriate for patients with pelvic stenosis, visceral hypertrophy, or large tumors.
is suitable for mid and lower rectal cancer. A review study concluded that the indication for TaTME is rectal adenocarcinoma, and contraindications include T4 tumor invasion of the vagina or prostate, no objective response to preoperative CRT of the tumor, tumor invasion of the EAS or levator muscle, BMI greater than 35, recurrent patients, and those who cannot tolerate pneumoperitoneum.
Surgical technique
TaTME is a new technique that allows distal and proximal transanal free rectum. Technical proponents believe that TaTME facilitates radical resection in a narrow or fixed pelvic cavity and guarantees a negative distal margin. Multiport laparoscopy, small-bore laparoscopy, or single-port laparoscopy can assist TaTME. some authors believe that the abdominal portion should be performed first, followed by the transanal portion, while others prefer to perform both simultaneously. Different types of platforms and even robotic TaTME have been reported.
The standard technique consists of two parts: abdominal surgery and transanal surgery. Most abdominal procedures are performed with high ligation of the submesenteric vessels, freeing the left colon and splenic flexure. The stool is drained through an ileal collaterals stoma, unless a permanent stoma is required.
In transanal surgery, the rectum is explored after placement of a self-fixing puller, and if the tumor is 3 cm above the anal verge, an interanal spreaders are excised after electrocautery incision via the dentate line. After complete resection of the entire rectal wall, the rectum is closed with purse-string sutures and the anterior segment of the anal canal is incised transanally for 4-4.5 cm for transanal platform placement, and CO2 is pressurized to 10-12 mmHg, which is also appropriate for the rest of the resection.
The anterior sacral plane is entered, the rectal mesentery is freed, and resection is performed cephalad along the avascular anterior sacral plane, consistent with the principles of TME. The resection continues medially, laterally, and anteriorly, freeing the perirectal margin, at which point rectal retraction should be avoided so that lateral resection does not become difficult. The sigmoid colon is freed after seeing the peritoneal reflex, and the two groups collaborate to complete the operation. The device and the specimen are removed via the anus, and the sigmoid colon should be resected close to the vascular root, and mesenteric and marginal artery dissection is completed simultaneously with the specimen dissection, and the proximal sigmoid colon and distal anorectal cuff anastomosis are performed.
For low to medium rectal tumors, after posing and self-fixing retraction, the platform is entered transanally and fixed in the anal canal, and the rectal mucosa is ruffled and sutured to keep it away from damage. The whole rectal wall was transected endoscopically, and the distal rectal mucosa was again sutured with pack sutures. The rectal mesentery was freed as above. The specimen was removed transanally, the colon was resected, and the rectal anastomosis was performed using an EEA 33 mm circular anastomosis.
Early postoperative results
No deaths were reported in the only review, and complications were 22.7%, mainly infectious complications such as pelvic abscesses and anastomotic fistulas. Another study showed postoperative complications of 26% and anastomotic leak of 5.3%.
Oncologic outcomes
The oncologic results of TaTME were obtained from non-randomized retrospective studies. the overall quality of TME was satisfactory. One study showed 10/136 positive CRMs, and most studies reported ≥12 lymph node acquisitions. A recent study showed 47 complete resections of the rectal mesentery, 9 near complete resections, 12 median lymph nodes, median radiographic and distal margins of 8 and 10 mm, respectively, 5.3% CRM involvement, 53 R0 resections, and a median overall survival of 96.4% at a median follow-up of 29 months.
Another review has shown the reproducibility of TaTME surgery, with positive CRM marginal results lower than APR and equal to LAR, comparable to rectal mesenteric resection and lymph node dissection. Although more studies are needed to confirm these results, results are currently available showing a significantly higher rate of complete rectal mesenteric resection with TaTME than with laparoscopic TME.
Functional results
Only one study reported a functional study, with 52/56 patients requiring a colostomy after ileostomy closure, 3 with severe fecal incontinence, and the remaining 49 without a stoma, with a median Wexner score of 4, 14 with a score of more than 7, and 13 reporting difficulty with bowel truncation and emptying.
In conclusion
While TaTME is safe and feasible, the expert consensus is that when TaTME is used for curative purposes, a standard board-approved protocol needs to be available and TaTME should only be performed by colorectal surgeons experienced in minimally invasive or transanal endoscopic procedures. More studies are needed to evaluate oncologic and functional outcomes.
Conclusion
ISR for rectal tumors in T1-3, within 30-35 mm of the anal verge, with or without IAS invasion, is technically feasible, has an acceptable complication rate, and has similar oncologic outcomes to LAP and APR, with acceptable QoL, whereas APR is more commonly used for locally progressive tumors.
APPEAR is a promising technique with the advantage of not damaging the dilation muscle, but it has significant complications as fewer studies have addressed it, and long-term oncologic and functional outcomes are unknown.
TEM and TAMIS are a treatment option for T1 rectal tumors, and according to the NCCN guidelines tumors need to meet a number of criteria. If the pathology report shows submucosal invasion as sm2-3, patients should be told that locally resected pT1sm2-3 tumors with a 20% local recurrence rate should be treated as T2 tumors.
The recommended treatment for T2 rectal tumors is TME without adjuvant therapy. Although still controversial, preoperative CRT followed by TEM/TAMIS appears to be a promising approach for the treatment of T1sm2-3 or T2 tumors.
TaTMEs need to be performed only when a standard protocol approved by the committee is available and by a colorectal surgeon experienced in minimally invasive or transanal endoscopic procedures.
In addition to selecting the correct procedure based on the patient’s tumor characteristics, care should be taken to screen patients who do not require surgery. The “watchful waiting” approach proposed by Habr-Gama et al. is suitable for patients who have achieved complete clinical remission after neoadjuvant CRT, with 5-year overall survival and disease-free survival rates as high as 100% and 92%.