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Transanal Approaches to Early Rectal Cancer: Transanal Endoscopic Microsurgery and Conventional Transanal Excision
Widespread introduction of screening programs has resulted in a significant increase in the early detection of rectal cancers. In addition, staging tools and treatment modalities for rectal cancer have greatly improved. As a consequence, there is an increasing interest in multimodal organ-preserving strategies in patients with early rectal cancer (ERC), including the use of local excision (LE) and chemoradiation therapy (CRT).
Until the 1990s, conventional transanal excision (TAE) with retractors was considered an oncologically adequate alternative to radical rectal resection for the treatment of ERC. However, the advent of the total mesorectal excision (TME) and the implementation of new endoscopic techniques, including transanal endoscopic microsurgery (TEM), have challenged the role of conventional TAE even in T1 rectal cancer patients. To date, abdominal rectal resection combined with TME is the current standard for the surgical treatment of rectal cancer. TEM is an attractive option in selected T1N0 cancer patients because it avoids the morbidity and the functional sequelae associated with radical surgery. Recently, its use in association with neoadjuvant CRT has been proposed in selected T2-N0 rectal cancer patients.
The aim of this chapter is to review surgical techniques and short- and long-term oncologic outcomes of TAE and TEM for ERC.
Early Rectal Cancer: Definition
There is no consensus regarding how to define an ERC ( Table 167B.1 ). Some classifications define ERC based on the degree of submucosal infiltration; the Haggitt levels estimate the submucosal invasion in pedunculated tumors, whereas the Kikuchi classification describes the depth of submucosal invasion in nonpedunculated lesions by dividing the submucosa in three parts: sm1, sm2, and sm3 T1 cancers.
TABLE 167B.1
Definitions of Early Rectal Cancer
| Classification | Description |
|---|---|
| Haggitt classification (pedunculated T1 cancers) | Level 1 : invasion of submucosa limited to polyp head Level 2 : invasion of submucosa of the polyp neck Level 3 : invasion of submucosa of the polyp stalk Level 4 : invasion of submucosa beyond the stalk |
| Kikuchi classification (nonpedunculated T1 cancers) | sm1 : invasion less than 1 mm sm2 : intermediate between sm1 and sm3 sm3 : invasion near to the muscularis propria |
| The Paris classification of superficial neoplastic lesions and its revised edition | A polypoid lesion may be
Nonpolypoid lesions are
Mixed types are
|
| EAES Consensus Conference | Early rectal cancer is a rectal cancer with good prognostic features that might be safely removed preserving the rectum, and that will have a very limited risk of relapse after local excision. |
EAES, European Association for Endoscopic Surgery.
The Paris classification of superficial neoplastic lesions and its revised edition represent the most recent attempt to classify ERC from a pathologic point of view. A tumor is defined as superficial when the depth of tumor infiltration is limited to the submucosa. A polypoid lesion may be pedunculated (0-Ip), sessile (0-Is), or with a mixed pattern (0-Isp). Nonpolypoid lesions are either slightly elevated (0-IIa, with elevation <2.5 mm above the level of the mucosa), completely flat (0-IIb), or slightly depressed (0-IIc). The mixed types include elevated and depressed lesions (0-IIa + IIc), depressed and elevated (0-IIc + IIa), and sessile and depressed (0-Is + IIc). The nondepressed types (i.e., 0-IIa, 0-IIb) might progress to polypoid or laterally spreading tumors.
Even though ERC is considered as a rectal cancer with low risk of lymph node metastases (T1-2N0), this definition does not thoroughly reflect the clinical impact of ERC on both treatment and survival. Therefore, a clinical definition has recently been proposed: ERC is a rectal cancer with good prognostic features that might be safely removed preserving the rectum, and that will have a very limited risk of relapse after LE.
Conventional Transanal Excision/Transanal Endoscopic Microsurgery
Preoperative Work-up
The preoperative work-up includes
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Clinical evaluation including digital rectal examination
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Complete colonoscopy to rule out the presence of synchronous colonic lesions
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Rigid proctoscopy to locate the lesion along the circumference and to measure the distance of the upper and lower limits from the anal verge
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Endoscopic ultrasound (EUS) to assess the depth of invasion of the tumor in the rectal wall
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Pelvic magnetic resonance imaging (MRI) to detect potential lymph node metastases
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Chest and abdominal computed tomography to rule out distant metastases
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Serum carcinoembryonic antigen (CEA) assay
Patient Preparation
Candidates for TEM/TAE of an ERC should be on a low-fiber diet the week before surgery and undergo a rectal enema 12 and 2 hours preoperatively. If violation of the peritoneal cavity is expected, a full bowel preparation with oral antibiotics is administered. Intravenous antibiotics, such as a second-generation cephalosporin and metronidazole, are administered before starting the operation and continued on the first postoperative day. Deep venous thrombosis prophylaxis is not routinely administered.
Conventional Transanal Excision
Indications
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T1N0 tumors located in the lower rectum (<10 cm from the anal verge)
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Mobile and polypoid lesions
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Tumors involving less than 1/3 of rectal circumference
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Tumors less than 3 cm in diameter
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G1-2 tumors
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No evidence of lymphovascular invasion (even though the preoperative evaluation of this parameter is challenging)
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