Definition of Colon and Rectum Carcinoma
According to the international documentation system, rectal carcinomas are tumors whose aboral margin, when measured with the rigid rectoscope, is 16 cm or less from the anocutaneous line [1, 2]. A distinction is made between
- the lower third (0–6 cm),
- the middle third (6–12 cm) and
- the upper third (12–16 cm) [3].
In the USA, on the other hand, tumors up to 12 cm and less from the anocutaneous line are referred to as rectal carcinomas, above the 12 cm limit they are counted as colon carcinomas [4].
Abbreviated TNM Classification of Colorectal Carcinomas [5]
| Stage | TNM | Depth of Infiltration/Tumor Spread
|
| I | T1N0 | Submucosa
|
| T2N0 | Muscularis propria | |
| II | T3N0 | Perirectal tissue: Mesorectum |
| T4N0 | T4a Visceral peritoneum T4b Other organs/structures
| |
| III | N1/2 | N1a 1 regional lymph node metastasis N1b 2–3 regional lymph node metastases N1c Satellites/tumor nodules in the mesorectum N2a 4–6 regional lymph nodes N2b >6 regional lymph nodes
|
| IV | M1 | M1a Metastases limited to one organ (liver, lung, ovary, non-regional lymph nodes, no peritoneal metastases) M1b Metastases in more than one organ M1c Metastases in the peritoneum with/without metastases in other organs |
Interdisciplinary Tumor Conference
Due to the complex therapy, all colorectal carcinomas should ideally be presented before therapy (e.g., surgery, chemotherapy) in an interdisciplinary tumor conference to create a joint treatment concept. In a study from Great Britain, patient survival could be significantly increased as a result [6].
A pre-therapeutic conference is particularly recommended for
- every rectal carcinoma
- every colon carcinoma in stage IV
- distant metastases
- local recurrences
- before every local ablative measure
In rectal carcinoma, for example, it can be clarified whether a neoadjuvant radiochemotherapy should be performed. In one study, the rate of affected circumferential margin in the surgical specimen could also be significantly reduced through pre-therapeutic case discussions [7]. If distant metastases are already present, it can be clarified whether a palliative/ablative concept is to be carried out or whether the distant metastases (e.g., liver metastases) are to be resected in one or two stages. Patients with distant metastases in whom chemotherapy was primarily initiated should be presented again to clarify whether secondary resectability of the metastases is possible. The rate of metastasis surgery has increased through the repeated presentation of patients in tumor conferences [8].
Preoperative Staging Diagnostics
The staging of rectal carcinoma includes
- complete colonoscopy, if necessary biopsy for secondary tumors
- abdominal sonography
- chest X-ray
- rigid rectoscopy with if necessary biopsy and height indication
- MRI pelvis with indication of the distance of the tumor to the mesorectal fascia
- Alternative to MRI rectal endosonography
The rectal-digital examination is also obligatory (assessment of sphincter function, estimation of sphincter preservation in low-lying rectal carcinomas).
In 5 % of colorectal carcinomas, secondary tumors are to be expected. Therefore, a complete colonoscopy should be performed preoperatively [9, 10, 11]. If this is not possible due to a stenosing tumor, preoperative imaging procedures should be considered (CT or MR colonography) [12]. Regardless of the imaging diagnostics, a colonoscopy should be performed 3 - 6 months after resection in these cases.
At the initial diagnosis of a rectal carcinoma, the frequency of distant metastases is 18 %. Distant metastases are found in 14 % of cases in the liver, lung metastases in 4 %, peritoneal metastases in 3 %, in non-regional lymph nodes in 2 %. To clarify liver metastases, abdominal sonography and a CT of the abdomen are performed as basic diagnostics [13, 14].
At the time of initial diagnosis, the tumor marker CEA is elevated in about 30 % of all colorectal carcinomas and should therefore be determined preoperatively. In tumor follow-up, CEA is a reliable indicator of recurrence in marker-expressing tumors and is also an independent prognostic factor in the case of liver metastases. The significance of CA 125 as a progression parameter for further treatment of proven peritoneal carcinomatosis is currently unclear [15, 16, 17].
Significance of Local Staging in Rectal Carcinoma
In rectal carcinoma, local staging is of decisive importance for further therapy planning:
| low risk T1 carcinoma: | local excision |
| high risk T1 and T2 carcinoma: | resection according to oncological criteria |
| T3 = infiltration of the mesorectum: | neoadjuvant therapy |
| T4 = infiltration into neighboring organs: | neoadjuvant radiochemotherapy |
For T3 carcinomas, data show that the extent of mesorectum infiltration (especially the distance from the mesorectal fascia) is of important prognostic significance [18]. In total mesorectal excision (TME), this plane represents the circumferential resection margin (CRM). If the carcinoma reaches up to 1 mm to the fascia or has already infiltrated it (CRM+), the risk for local recurrences is significantly increased [18]. Another prognostic factor is lymph node involvement [19].
In a meta-analysis from 2004, in which the data on endosonography, MRI and CT up to 2002 were analyzed, sonography showed the highest accuracy for T1 carcinomas [20], which was confirmed in a more recent meta-analysis [21]. An alternative to endosonography is MRI with endorectal coil (more expensive, unpleasant for patients, hardly available). Compared to MRI and CT, endosonography again showed higher sensitivity in differentiating T2 and T3 carcinomas [20], whereas for T4 carcinomas there is no significant difference between the various imaging procedures. For the depiction of the mesorectal fascia and its relationship to the tumor, MRI shows the highest sensitivity [22]. Spiral CT is an alternative for assessing the fascia [23], in endosonography the fascia is not depicted.
Radical Surgical Therapy of Rectal Carcinoma
The curative, radical resection of rectal carcinoma usually includes the resection of the primary tumor in healthy tissue as well as the partial or total removal of the mesorectum and thus the regional lymphatic drainage area [24]. Only in strictly selected cases is curative resection possible through local measures (full-wall excision).
When adhering to the criteria of oncological surgery, the following surgical procedures are to be regarded as equivalent depending on tumor location, relationship to the dentate line and levator sling, depth of infiltration and sphincter function:
- low anterior rectal resection
- abdominoperineal rectal extirpation
- intersphincteric rectal resection (abdominoperineal rectal resection)
Oncological Principles:
1. Removal of the regional lymphatic drainage area with ligation of the inferior mesenteric artery at least distal to the origin of the left colic artery. The value of lymph node dissection at the trunk of the inferior mesenteric artery proximal to the origin of the left colic artery is not established [25 - 28]. The same applies to the dissection of the lateral lymph nodes along the internal iliac artery including its branches [31 - 34].
2. Complete removal of the mesorectum (TME) in carcinoma of the middle and lower rectal third and partial mesorectum excision in carcinoma of the upper rectal third by sharp dissection between fascia pelvis visceralis and parietalis along anatomical structures [29, 30].
3. Maintenance of an appropriate safety margin
- Upper rectal third : horizontal ligation of the rectum with partial mesorectum excision 5 cm distal to the macroscopic tumor margin [29, 36 - 39]*
- Middle and lower rectal third: TME to the pelvic floor with sparing of the superior hypogastric plexus, the hypogastric nerves and the inferior hypogastric plexus [40 - 42]
-> Low-Grade-TU good or moderate differentiation in the lower third safety margin of 1-2 cm sufficient
-> for High-Grade-TU > 2 cm [43 - 47]
* Rationale: In T3 and T4 tumors, satellite nodules or lymph node metastases can rarely occur up to 4 cm distal to the macroscopic tumor margin.
Reconstruction after Total Mesorectal Excision
After TME with subsequent sphincter-near anastomosis, the following reconstruction procedures are considered:
- straight colo-anal anastomosis
- Colon J-Pouch
- transverse coloplasty
- side-to-end anastomosis
Straight colo-anal anastomoses lead especially in the first two postoperative years to increased stool frequency as well as poorer continence and quality of life and are therefore not recommended [48]. The advantages of the Colon J-Pouch in terms of functional outcome are best documented [48, 49]. To avoid evacuation problems, the limb length should not exceed 6 cm when creating the J-Pouch [50]. In almost 75 % of cases, the creation of a J-Pouch is technically possible [49]. From a functional point of view, the side-to-end anastomosis is probably equivalent to the Colon J-Pouch [51], the transverse coloplasty is inferior to the pouch [52].
Stoma Creation
In radical surgery of rectal carcinoma with TME and low anastomosis, a temporary stoma should be placed upstream. This can reduce morbidity (anastomotic leaks, urgent relaparotomies) [53]. Colostomy and ileostomy are considered equivalent, although current meta-analyses favor the ileostomy [54, 55]. The stoma position should be marked preoperatively. The ileostomy should be created prominently (> 1 cm), the colostomy slightly elevated.
Local Surgical Procedures for Rectal Carcinoma
Local tumor excision (full-wall excision) as a sole measure with curative intent (R0 resection) is oncologically sufficient for pT1 carcinomas under the following conditions [56 - 59]:
- maximum tumor diameter 3 cm
- good or moderate differentiation
- no lymph vessel invasion (low-risk histology)
Compared to radical surgery, even in low-risk cases, a higher risk for local recurrences is to be expected with simultaneously lower morbidity and lethality, so that these risks must be weighed against each other [60, 61]. Studies suggest that the technique of transanal endoscopic microsurgery is superior to open transanal excision using retractors [62, 63].
In T1 high-risk carcinomas (G3/4 and/or lymph vessel invasion) and in T2 carcinomas, the occurrence of lymph node metastases is 10 - 20 %, so that sole local excision is not recommended [64, 65].
Laparoscopic Surgery
With appropriate expertise of the surgeon and suitable selection, laparoscopic resection of a colorectal carcinoma can be performed with the same oncological results compared to the open surgical procedure. In the short-term course, perioperative morbidity is lower with minimally invasive procedures with unchanged overall morbidity and lethality [66]. In the long-term course, no differences were found between laparoscopic and conventional surgery for the rate of incisional hernias and adhesion-related relaparotomies nor for tumor recurrences [67, 68]. The British CLASSIC study also confirms the oncological safety of laparoscopic surgery in colorectal carcinomas [69, 70].