Introduction
The treatment of early rectal cancer has been a controversial subject for several decades. Radical proctectomy with total mesorectal excision (TME) is the gold standard for patients with tumors localized to the bowel wall. The average local recurrence (LR) rate for stage I rectal cancer after TME approximates 2%, and 5-year survival is as high as 95%. However, the morbidity associated with radical proctectomy is considerable, with postoperative complication rates approaching 35%, and the mortality rate after abdominal perineal resection (APR) has been reported to be up to 5%. Both low anterior resection (LAR) and APR are associated with significant rates of long-term sexual and urinary dysfunction. Bowel function after restorative resection is compromised in at least one third of all patients, and after APR, creation of a permanent stoma is associated with an 80% risk of long-term complications.
Local excision (LE) of rectal cancer was first introduced by Kraske in the 1880s. It did not become popular until the 1960s, when Mason introduced the transsphincteric approach. The posterior transsphincteric approach is well suited to distal tumors located in the anterior wall of the rectum. In many centers, Mason’s procedure is the preferred approach for the repair of recto-ureteral fistulae because of the access it provides. Fecal incontinence is the main complication, although rates of less than 1% have been reported in some series.
Parks was the first to describe transanal excision (TAE) without division of the anal sphincter for rectal cancer, using a specially designed set of speculums to gain access to the tumor. In the 1980s, a novel platform for transanal surgery was introduced, known as transanal endoscopic microsurgery (TEM). Since then two additional platforms, transanal endoscopic operation (TEO) and transanal minimally invasive surgery (TAMIS), have also been developed. In each of these three approaches, the rectum is distended by insufflation of carbon dioxide and the tumor is removed under direct endoscopic visualization, using either specially designed or conventional laparoscopic instruments. These platforms allow the removal of tumors located high in the rectum, beyond the reach of the conventional TAE.
The advantages of LE are lower rates of mortality and morbidity, with fewer long-term functional sequelae than radical resection. However, LE is a compromise oncologically because it is associated with a higher risk of LR and does not offer an opportunity to directly examine local nodes. Current National Comprehensive Cancer Network (NCCN) guidelines support the use of LE only in the treatment of carefully selected T1 rectal cancers. The oncologic outcomes for local excision of T2 tumors remain unacceptably high.
Apart from local excision, two methods are used for local destruction of rectal cancer: endocavitary contact radiation (ECR) and electrocautery. Both achieve destruction of the tumor, but neither provides tissue specimens for pathologic examination. ECR has the benefit of being an outpatient procedure and is typically performed with use of a local anesthetic and sedation; electrocoagulation requires induction of general anesthesia and a hospital stay, similar to LE. As TAE rises in popularity, these destructive techniques are falling out of favor. However, ECR may still have a role, especially in the treatment of frail patients.
In this chapter, we will describe local treatment of rectal cancer. We will review patient selection and the techniques and outcomes associated with these approaches. Given the intense focus and research on LE for rectal cancer and its increasing popularity during the past decade, we will preferentially focus on these modalities.
Preoperative Evaluation
Evaluation of all patients diagnosed with rectal cancer should include a full medical history, physical examination, and baseline carcinoembryonic antigen serum level. Digital rectal examination allows direct assessment of the location, size, and fixity of low tumors and their relationship to the sphincter complex.
Although most patients with newly diagnosed rectal cancer have already had a colonoscopy before referral to a surgeon, a proctoscopy should be performed to confirm the location of the tumor. A full colonoscopy should be performed before treatment for patients who have not already had this procedure.
Endorectal ultrasound (ERUS), magnetic resonance imaging (MRI), and computed tomography (CT) are routinely used in the staging of rectal cancer. ERUS is perhaps the most valuable tool in staging early rectal tumors. It provides high-resolution imaging of the different histologic layers of the bowel wall and is excellent for delineating T stage in early-stage rectal cancers. It can also provide short-range information about nodal status and demonstrate involvement of the mesorectum. MRI with use of an endorectal coil also images tumors within the bowel wall very accurately, although the technology is not widely used. Phased-array MRI has rapidly become the gold standard in the preoperative staging of rectal cancer. It provides high-resolution images of the rectum, mesorectum, surrounding pelvic structures, and the muscles of the pelvic floor, in multiple planes. MRI is especially useful in staging advanced tumors, particularly in defining the level of invasion into the mesorectum, nodal status, and the relationship of the tumor to the mesorectal fascia. Unlike ERUS, MRI does not differentiate the T stage of tumors confined to the bowel wall. A CT scan of the chest, abdomen, and pelvis should also be performed to exclude metastatic disease.
The patient’s functional status and baseline bowel function should be assessed before planning surgery. Some patients may not be good candidates for TME because of significant comorbidities, and some may refuse a permanent colostomy. These patients may benefit from transanal LE as a noncurative procedure. In other cases, poor preoperative bowel function and incontinence may diminish some of the benefits of LE, making TME with a permanent stoma the better option.
Initial Selection
The ideal candidate for LE has a superficial, mobile tumor that is localized to the rectal wall (T1). If cure is the aim, there should be no evidence of nodal involvement or distal metastases. Although tumor size itself is not an absolute contraindication to LE, larger tumors are often more advanced and are more likely to have metastasized to the regional lymph nodes. Therefore, LE is not recommended for tumors that encompass greater than 40% of the circumference of the rectal wall or measure more than 4 cm in diameter.
In general, patients with tumors in the distal rectum are the best candidates for LE. These patients are most likely to benefit from LE because TME would require an APR with a permanent colostomy or a coloanal anastomosis. Such tumors are also easier to reach with conventional TAE techniques. However, the new transanal endoscopic platforms allow removal of tumors located in the mid and upper rectum.
Surgical Technique
Patient Preparation
Patients should undergo mechanical bowel preparation and take nothing by mouth for all of the surgical approaches described in the following sections. Bowel preparation greatly facilitates visualization during surgery. Sequential calf compression devices are applied, and preoperative antibiotics are administered. A Foley catheter is placed to decompress the bladder.
We routinely use perioperative thromboprophylaxis with unfractionated or low-molecular-weight heparin. At baseline, patients undergoing LE for rectal cancer are at a higher risk of venous thromboembolism because of their cancer diagnosis. Overall, colorectal surgery, especially in the pelvis, carries a higher risk of venous thromboembolism than does general surgery, but it is unclear if these data are generalizable to transanal procedures. There does not appear to be any increased risk from use of the lithotomy or jackknife position during LE, and at least one large study has suggested that this positioning is protective. Current recommendations by the American College of Chest Physicians support thromboprophylaxis in these patients, with optimal management consisting of combined use of low-dose heparin and compression devices.
Transanal Excision
Good visualization is crucial to a successful TAE. The surgeon should wear a headlight. Positioning is aimed at providing adequate exposure to the tumor. For anterior tumors, the patient is in the prone jackknife position. The operating table should be in a slight Trendelenburg position. For posteriorly situated tumors, the patient is in a modified lithotomy position, again with the table in the Trendelenburg position. Care should be taken to provide adequate padding at all weight-bearing points. TAE can often be performed with use of monitored sedation, although general anesthesia may need to be induced depending on the tumor size and location.
The buttocks are taped apart and a Lone Star retractor (CooperSurgical, Trumbull, Conn.) is used to open the anus, especially in the setting of very distal tumors. Hill-Ferguson, Pratt bivalve, or other retractors are used to expose the rectum. For more proximal tumors, narrow Deaver and short Wiley retractors are helpful.
We begin by marking the intended incision line with cautery, with at least 1-cm margins around the tumor. A local anesthetic with epinephrine can be infiltrated under this margin for additional hemostasis. Especially for proximal tumors, stay-sutures are placed laterally and beyond the incision line in order to pull the tumor closer to the anal orifice. A full-thickness excision is carried out with electrocautery, beginning at the far end (the more proximal) and working distally. Excision extends into the mesorectum, and the specimen is undercut through the perirectal fat. Some surgeons advocate taking a conical margin of the entire mesorectum. During deeper excision anteriorly, care must be taken to avoid injuring the vagina in females and the prostate in males.
The wound should then be extensively irrigated with water. The defect is closed with full-thickness bites transversely; these bites can be with continuous or interrupted sutures, depending on the tension of the wound. Proctoscopy should be performed to confirm the patency of the lumen.
Two doses of prophylactic antibiotics are typically administered in the perioperative setting—one dose within 30 minutes of beginning the procedure, and one dose postoperatively. However, some centers routinely prescribe additional prophylaxis. In a single-institution series from 2010, Bignell and colleagues reported a pelvic sepsis rate of 6.5% after TEM for tumors within 2 cm of the dentate line. For more proximal tumors, the rate was 0.5%. As a result, it is now routine for patients with very distal tumors to be prescribed 5 days of antibiotic prophylaxis postoperatively. Other groups have reported use of similar extended courses of antibiotics.
Transanal Endoscopic Microsurgery/Transanal Endoscopic Operation
The TEM platform is manufactured by the Richard Wolf Medical Instruments Corporation (Vernon Hills, Ill.). It includes a selection of large-bore operating proctoscopes, with some beveled and some flat. The proctoscope is fitted with a carbon dioxide insufflation system and binocular optics that provide tridimensional visualization. The TEM instruments, including a grasper, electrocautery, and other devices, are specifically designed and angled for use in the proctoscope.
More recently, The Storz Corporation (El Segundo, Calif.) has developed a simplified TEO platform that also uses a large-bore operating rectoscope. However, the insufflation, instrumentation, and optics are those of conventional laparoscopy. This platform is less expensive but does not provide tridimensional visualization and has less sophisticated instrumentation than the TEM platform.
As with TAE, patients are placed in either the prone jackknife or modified lithotomy position; the goal is to have the tumor positioned inferiorly in the surgeon’s field of view. Lateral tumors may require the patient to be in the lateral decubitus position. Patients are positioned with the aid of beanbags. Throughout the case, the operating table may have to be moved sideways or placed in the Trendelenburg position for optimal visualization, so it is important that the patient be well secured to the table.
Once the patient is positioned, the TEM/TEO platform is mounted onto the table by means of a support arm, and after gentle anal dilatation, the proctoscope is inserted. The rectum is insufflated to 15 to 26 mm Hg. Full-thickness excision is performed, as described in TAE, but with use of the specialized instruments inserted through the proctoscope. At the conclusion of the excision, the defect is closed with interrupted sutures. In cases in which there is too much tension, or when the cavity left behind in the rectum after closure is very large, the defect may be left open to prevent abscess and dehiscence. Leaving the defect open is not an option if there is entry into the peritoneal cavity; such defects must be closed. Meticulous hemostasis should be achieved because bleeding is among the most common postoperative complications. Luminal patency is checked by proctoscopy at the conclusion of the case, and the rectum is irrigated and packed. Postoperative antibiotics are administered.
Neither TEM nor TEO is well suited to resection of very distal tumors because their platforms cannot be stably mounted, nor can a good seal be created. However, both are ideal approaches for proximal tumors. The surgeon is able to advance the scope to the level of the tumor, permitting excision under direct visualization. The use of specialized and/or laparoscopic instruments allows for full-thickness resections as high as the peritoneal reflection (which would not be possible by TAE). Because entry into the peritoneal cavity is possible and occasionally requires conversion to an abdominal approach in order to close the resultant wound, most TEM and TEO procedures are performed after induction of general anesthesia.
Transanal Minimally Invasive Surgery
The most recent innovation in transanal excision is TAMIS, which uses the laparoscopic SILS Port (Covidien USA, Bolder, Colo.) as the platform. After the patient is positioned as indicated in the TEM and TEO procedures, the SILS Port is lubricated and inserted into the rectum. The rectum is insufflated, and traditional laparoscopic instruments are used for the resection. This technique has also been used in conjunction with robotic surgery. As with TEM and TEO, very distal tumors are not amenable to TAMIS.
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