Aim: Multidetector computed tomography (MDCT) is the main preoperative decisionmaking tool in colon cancer treatment, thus the validation of daily clinical practice is warranted. The only published study validating the accuracy of MDCT in a national cohort was performed more than a decade ago. With neoadjuvant chemotherapy for patients with preoperatively assessed locally advanced cancer and the emergence of other personalized treatments we aimed to validate the accuracy of MDCT in a national cohort. Method: The study is based on the Danish Colorectal Cancer Group (DCCG) database and included all Danish patients diagnosed with primary colon adenocarcinoma between January 2015 and December 2018. The primary study outcome was the accuracy of MDCT in identifying patients with locally advanced disease. The secondary outcomes were the accuracy of predicting UICC Stage I based on predicting the tumour category (pT3-T4 versus pT1-T2) and lymph node metastasis. Results: A total 3465 patients were included in the analyses regarding locally advanced colon cancer. The sensitivity and specificity were 0.61 (0.58-0.64) and 0.85 (0.83-0.86), respectively, for CT to predict locally advanced disease. The sensitivity and specificity were 0.63 (0.59-0.66) and 0.80 (0.78-0.81), respectively, for predicting UICC Stage I in 4496 patients. Thirty six per cent of the patients assessed as having locally advanced disease and 58% assessed as Stage I were misclassified by MDCT. Conclusion: The present standard in Denmark questions whether the implementation of personalized medicine such as neoadjuvant adjuvant chemotherapy and tailor-made resections based on MDCT is justified.

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Aim To investigate whether intramesocolic plane dissection assessed on fresh specimens by the pathologist is a risk factor for recurrence after complete mesocolic excision for sigmoid cancer when compared with mesocolic plane dissection. Method Single‐centre study based on prospectively registered data on patients undergoing resection for UICC stage I–III sigmoid colon adenocarcinoma during the period 2010–2017. The patients were stratified into either an intramesocolic plane group or a mesocolic plane group. Primary outcome was risk of recurrence after 4.2 years using inverse probability treatment weighting and competing risk analyses. Results Of a total of 332 patients, two were excluded as the specimen was assessed as muscularis propria plane, 237 (72%) specimens were deemed as mesocolic and 93 (28%) as intramesocolic. The 4.2‐year cumulative incidence of recurrence after inverse probability treatment weighting was 14.9% (10.4–19.3) in the mesocolic group compared with 9.4% (3.7–15.0) in the intramesocolic group, thus the absolute risk difference between the mesocolic plane and intramesocolic plane was 5.5% (−12.5–1.6; p = 0.13) in favour of the intramesocolic group. Conclusion Intramesocolic plane dissection was not a risk factor for recurrence after complete mesocolic excision for sigmoid cancer when compared with mesocolic plane dissection. No difference in risk of local recurrence, death before recurrence, and in overall survival after 4.2 years was observed between the two groups. With less than 1% of the specimens deemed as muscularis propria plane dissection, the classification appears unusable for the risk prediction of sigmoid colon cancer.

Aim: Dissection in the mesocolic plane is considered by some medical professionals to be crucial in complete mesocolic excision. We aimed to assess whether intramesocolic plane dissection is associated with a risk of recurrence after complete mesocolic excision for right-sided colon cancer. Method: This is a single-centre study based on prospectively registered data on patients undergoing resection for Union for International Cancer Control Stage I-III right-sided colon adenocarcinoma during the period 2010-2017. Patients were stratified in an intramesocolic plane group or a mesocolic plane group based on a prospective assessment of fresh specimens by a pathologist. Primary outcome was the 4.2 year risk of recurrence after inverse probability treatment weighting and competing risk analyses.Results: Of 383 patients, 4 (1%) were excluded as the specimen was assessed as muscularis propria plane, 347 (91.6%) specimens were deemed as mesocolic and 32 (8.4%) as intramesocolic. The 4.2 year cumulative incidence of recurrence after inverse probability treatment weighting was 9.1% (95% CI 6.0%-12.1%) in the mesocolic group compared with 14.0% (3.6%-24.5%) in the intramesocolic group with an absolute risk difference in favour of mesocolic plane dissection of 4.9% (−5.7 to 15.6, p = 0.37). No difference was observed in the risk of local recurrence, death before recurrence or overall survival after 4.2 years between the two groups. Conclusion:Mesocolic plane dissection can be achieved in more than 90% of patients.The classification seems to be a guide for good surgical practice and not to be used for research purposes.