Minimally Invasive Oncological Colon Surgery
In the treatment of colorectal carcinomas, the surgical resection of the tumor-bearing bowel segment is essential. The fundamental oncological principle involves the central ligation of the arterial blood supply with the performance of a complete mesocolic excision (CME) and the complete removal of all lymph nodes associated with the respective bowel segment [1, 2].
Numerous randomized controlled trials with strict inclusion and exclusion criteria and clear guidelines for the qualification of surgeons, as well as registry data and population-based studies, demonstrate the equivalence of laparoscopic colon resections (LCR) compared to conventional open resections (OCR) in the oncological setting [3-13].
Compared to OCR, LCR shows a longer operation time, less intraoperative blood loss, reduced postoperative analgesic requirement, less postoperative bowel atony, and a shorter hospital stay [4, 6, 10, 14, 15, 16]. Extensive RCTs show no statistically significant difference in postoperative mortality between OCR and LCR [3, 4, 6,17], while population and registry-based studies report it as lower in the LCR group [8, 11, 13].
In deciding between OCR or LCR, tumor location, low T-stage, smaller estimated tumor size, younger patient age, female gender, type of clinic, and elective setting are predictors favoring the decision for LCR [9, 11, 18].
Even in colorectal carcinomas, the patient's prognosis depends on the number of lymph nodes removed with the resectate [1, 19]. In large RCTs, the number of lymph nodes removed in the LCR group is comparable to that in the OCR group [4-6, 15, 17].
Many studies were conducted before the establishment of the CME principle. However, a 2017 meta-analysis showed that resections under CME standards regarding the number of lymph nodes removed and the surface area of the resected mesocolon largely maintain comparable resectate quality between LCR and OCR [20].
There is some heterogeneity in the reported conversion rates to conventional open procedures. In large RCTs, it ranges from 11 to 25% [3-6], while in population and registry-based studies, it ranges from 5.7 to 19% [11, 21-23]. Over time, with the application of LCR, increasing surgeon experience, and experience in patient selection, the conversion rate decreases (11.8% → 8.6% [21]). In the MRC-CLASSIC trial, conversion is consistently associated with a significantly higher risk of recurrence and disease-associated mortality up to the 10-year follow-up [24]. Conversion is associated with a higher risk of postoperative complications [22].
Risk factors for conversion include:
- high body mass index
- higher ASA classification
- abdominal previous surgeries
- male gender
- tumor location in the transverse colon and left hemicolon
In a 2012 study with a conversion rate of 15.8%, 20.8% of procedures were on the transverse colon, 20.7% on the left hemicolon, 15.6% on the right hemicolon, and 14.3% on the sigmoid colon [25]. Other factors influencing the conversion rate include local tumor extension and the frequency of LCRs performed in a clinic [18, 21, 26].
Whether a new surgical procedure (here: LCR) can establish itself in the oncological setting depends on its comparability, possibly even superiority, to the currently established procedure (OCR) in terms of overall survival, disease-free survival, and recurrence rate. The initially postulated increased risks of implantation metastases of the abdominal wall (trocar insertions) and tumor cell dissemination were quickly refuted [27-29]. Large RCTs show comparability of LCR to OCR for overall survival and disease-free survival, as well as the frequency of local recurrences and distant metastases [27, 29-32]. Some registry data and population-based studies indicate a superiority of LCR over OCR, as in the work of Völkl et al [9]. However, a significant difference is only evident for stages T1 to T3, not for T4 and/or cases with lymph node metastases. Another study also describes a significant survival advantage after LCR, regardless of tumor location and T-stage [7].
In locally advanced cases (T4a and T4b), current studies suggest that even in a T4 situation, LCR can lead to satisfactory oncological outcomes and appears safe and not inferior to OCR [9, 33, 34].