Surgical Therapy of Colon Cancer
The progress in the treatment of colon cancer over the last 30 years is attributed to an increasing individualisation of therapy, the consistent implementation of surgical-oncological principles, more aggressive therapy regimens in the metastatic stage, and the use of minimally invasive surgical techniques. Standardised treatment concepts in multimodal tumour therapy have led, among other things, to an increase in the average five-year survival rate from 65% to over 85% and a reduction in the locoregional recurrence rate from an average of over 13% to under 2% in non-metastatic colon cancer in UICC stages II and III. [10]. In the metastatic stage, five-year survival rates of over 40% are now achieved in 20% of patients [19].
Surgical-Oncological Principles
Of crucial importance for prognosis is the en-bloc resection of the tumour-bearing colon segment with systematic locoregional lymphadenectomy. The systematic lymphadenectomy with a high yield of potentially metastatically involved lymph nodes is the basis for a standardised classification of lymph node status, the resulting therapy recommendation, and the patient's prognosis.
Lymphogenic metastasis of colon cancer occurs centrally via the paracolic lymph nodes, which are affected in 70% of node-positive patients, as well as via the intermediate lymph nodes to the lymph nodes along the main artery. The longitudinal drainage to the sides of the tumour occurs via the paracolic lymph nodes with a lateral spread of a maximum of 10 cm [25, 26]. The extent of resection is thus oriented to the supply area of the radicularly divided main arteries and should also be at least 10 cm on both sides of the tumour. As the last lymph node station, the main lymph nodes are located centrally at the origin of the corresponding main vessels from the major vessels.
Due to the increasing standardization of en-bloc resection with systematic lymphadenectomy, an improvement in overall prognosis in the curative situation has been achieved over the past 20 years, even against the background of established chemotherapy [16]. Retrospective studies have demonstrated a correlation between the number of lymph nodes examined and the stage-independent prognosis [8, 13].
The concept of the sentinel lymph node has not become established as a staging tool in colon surgery outside of studies [3, 4]. Although the evidence is inconsistent, the current S3 guideline "Colorectal Cancer" recommends the extirpation and histological processing of at least 12 lymph nodes as a quality criterion [21].
In addition to systematic lymphadenectomy, the concept of complete mesocolic excision (CME) also aims at a maximum reduction in the number of local recurrences by increasing the radicality and quality of the resection. The technique was published in 2009 by Hohenberger et al. and is based on three pillars [16, 24]:
- Dissection along the embryonic layers, whereby the two mesocolic fascial layers of the resection area are preserved and possible tumour cell dissemination is to be avoided.
- The strictly close-to-origin division of the respective main vessels enables a maximum lymph node yield as well as maximum local radicality towards the centre.
- An adequate length of the resectate ensures maximum paracolic lymphadenectomy.
Data from Denmark, Sweden, and Germany show that the CME technique is associated with better disease-free survival in patients with colon cancer in UICC stages I – III than conventional colon resection [5, 6, 18].
Minimally Invasive Surgery
Mono- and multicentre RCTs (KOLOR, COST, CLASSIC-Trail) showed no differences between laparoscopic and open techniques in colon cancer surgery regarding surgical-oncological quality indicators (R-status, number of lymph nodes) and long-term results (tumour recurrences, survival) with appropriate expertise of the surgeon [7, 11, 14]. As an advantage of minimally invasive surgery, a relatively low perioperative morbidity with unchanged overall morbidity and mortality was demonstrated in the short-term course [23]. According to the current S3 guideline "Colorectal Cancer," laparoscopic resection of colon cancer can therefore be performed in suitable cases with appropriate experience of the surgeon [21]. There is currently no data basis for the application of NOTES in colon cancer.
Multimodal Tumour Therapy
Numerous studies demonstrate the importance of drug tumour therapy in non-metastatic colon cancer. An adjuvant chemotherapy in UICC stage III is associated with a significant improvement in prognosis of about 20% overall survival [22]. In stage II, patients with risk factors (T4 tumour, tumour perforation, emergency interventions, number of examined/extirpated lymph nodes < 12) have a significantly worse prognosis than patients in the same stage without risk factors and should therefore receive adjuvant chemotherapy [21].
The role of neoadjuvant chemotherapy in the treatment of locally advanced colon cancers has been investigated in recent years. A randomised study from the UK showed that combined neoadjuvant/adjuvant chemotherapy (oxaliplatin, folinic acid, and 5-FU) vs. adjuvant chemotherapy alone in locally advanced colon cancers resulted in a lower rate of R1 resections and significant downstaging. Tumour progression during ongoing neoadjuvant chemotherapy was not observed [2, 12]. Studies have shown that computed tomography is suitable for identifying locally advanced colon cancers in terms of the T-category and thus selecting for neoadjuvant chemotherapy or preoperatively assessing the response to chemotherapy [1, 20]. However, oncological long-term results are still pending.
Liver and Lung Metastases
In the metastatic situation, the five-year survival rate is below 10%. Through drug tumour therapy (combination of dual therapy and antibodies) and the more aggressive indication for metastasis resection, the prognosis for about 20% of metastatic patients improves considerably, with a five-year survival rate of up to 50% [15]. Using various chemotherapy protocols, response rates of up to 60% and an R0 resection rate of up to 15% are achieved [9].
Peritoneal Carcinomatosis
If peritoneal carcinomatosis is already present in colon cancer, the indication for cytoreductive surgery followed by hyperthermic intraperitoneal chemotherapy (HIPEC) can be reviewed. The use of this combination therapy has shown a significant survival advantage in terms of extending median survival from 12.6 to 22.3 months [27]. The Peritoneal Cancer Index (PCI) is used to determine the extent of peritoneal carcinomatosis. If the PCI value is below 20 in patients without additional extra-abdominal metastases, operative cytoreduction with HIPEC can be performed in specialized centers, provided an R0 resection is possible [21].
Perioperative concept
The ERAS concept ("enhanced recovery after surgery") of multimodal postoperative rehabilitation in gastrointestinal surgery is implemented in most clinics in this country in a partially modified form. The aim of the concept is to quickly manage the pathophysiological changes triggered by the surgical intervention, such as fatigue, bowel atony, and insulin resistance. The concept includes, among other things, the early removal of gastric tubes and intra-abdominal drains, early oral nutrition, stimulation of bowel motility, sufficient analgesia (epi-/peridural), and early mobilization. Numerous studies have shown that the ERAS concept can achieve a significant reduction in length of stay with a significantly lower complication rate [17].