Surgical Therapy of Colon Cancer
The progress in the treatment of colon cancer over the past 30 years is due to an increasing individualization 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. Standardized treatment concepts in multimodal tumor 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 the prognosis is the en-bloc resection of the tumor-bearing colon segment with systematic locoregional lymphadenectomy. The systematic lymphadenectomy with a high yield of potentially metastatic lymph nodes is the basis for a standardized classification of lymph node status, the resulting therapy recommendation, and the prognosis of the patient.
The 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 tumor 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 radially resected main arteries and should also be at least 10 cm on both sides of the tumor. 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 the overall prognosis in the curative situation has been achieved over the past 20 years, also 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 established itself as a staging instrument in colon surgery outside of studies [3, 4]. Although the study situation 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 to maximize the reduction of the number of local recurrences by increasing the radicality and quality of the resection. The technique was published by Hohenberger et al. in 2009 and is based on three pillars [16, 24]:
- Preparation along the embryonic layers, whereby the two mesocolic fascial layers of the resection area are preserved and possible tumor cell dissemination is to be avoided.
- The strict close-to-origin resection of the respective main vessels allows for maximum lymph node yield and maximum local radicality towards the center.
- 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 multicenter RCTs (KOLOR, COST, CLASSIC-Trail) found no differences between laparoscopic and open techniques in colon cancer surgery in terms of surgical-oncological quality indicators (R-status, number of lymph nodes) and long-term results (tumor 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 shown 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 Tumor Therapy
Numerous studies demonstrate the importance of drug tumor 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 tumor, tumor 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 randomized 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. Tumor 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]. 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 tumor therapy (combination of dual therapy and antibodies) and more aggressive indication for metastasis resection, the prognosis for about 20% of metastatic patients improves significantly 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 an extension of 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].