The objective of this study is to assess transanal endoscopic microsurgery (TEM) as a surgical strategy for stage I rectal cancer. The literature lacks level I and level II evidence of the oncologic competence of TEM. Three randomized controlled, one prospective, and seven retrospective comparative studies were evaluated. End-points included perioperative outcomes, margin involvement, disease-free and overall survival, and recurrence. The number of patients with major (odds ratio (OR) = 0.24,95% confidence interval (CI) 0.07–0.91) and overall postoperative complications (OR = 0.16, 95% CI 0.06-0.38) were significantly lower in TEM. The disease-free survival was higher in standard resection (SR) group compared with TEM (OR = 0.46, 95% CI 0.24-0.88). The number of patients with positive margins were less in the SR group (OR = 6.49, 95% CI 1.49-24.91), which was associated with lower local recurrence (OR = 4.92,95% CI 1.81-13.41) and overall recurrence rate (OR = 2.03, 95% CI 1.15-3.57). No survival advantage was observed in favor of either procedure. TEM had lower rate of positive margins and longer disease-free survival when compared with transanal excision (TAE). TEM seems to be superior to SR concerning morbidity whilst less effective in obtaining negative surgical margins, and it is associated with higher local and overall recurrence. No survival advantage was observed in favor of either procedure. Unfavorable tumor preoperative histology does not seem to influence the selection between TEM and SR. TEM is more effective than TAE in obtaining negative surgical margins and shows a greater disease-free survival.

Background The molecular profile of early-onset colonic cancer is undefined. This study evaluated clinicopathological features and oncological outcomes of young patients with colonic cancer according to microsatellite status. Methods Anonymized data from an international collaboration were analysed. Criteria for inclusion were patients younger than 50 years diagnosed with stage I–III colonic cancer that was surgically resected. Clinicopathological features, microsatellite status, and disease-specific outcomes were evaluated. Results A total of 650 patients fulfilled the criteria for inclusion. Microsatellite instability (MSI) was identified in 170 (26.2 per cent), whereas 480 had microsatellite-stable (MSS) tumours (relative risk of MSI 2.5 compared with older patients). MSI was associated with a family history of colorectal cancer and lesions in the proximal colon. The proportions with pathological node-positive disease (45.9 versus 45.6 per cent; P = 1.000) and tumour budding (20.3 versus 20.5 per cent; P = 1.000) were similar in the two groups. Patients with MSI tumours were more likely to have BRAF (22.5 versus 6.9 per cent; P < 0.001) and KRAS (40.0 versus 24.2 per cent; P = 0.006) mutations, and a hereditary cancer syndrome (30.0 versus 5.0 per cent; P < 0.001; relative risk 6). Five-year disease-free survival rates in the MSI group were 95.0, 92.0, and 80.0 per cent for patients with stage I, II, and III tumours, compared with 88.0, 88.0, and 65.0 per cent in the MSS group (P = 0.753, P = 0.487, and P = 0.105 respectively). Conclusion Patients with early-onset colonic cancer have a high risk of MSI and defined genetic conditions. Those with MSI tumours have more adverse pathology (budding, KRAS/BRAF mutations, and nodal metastases) than older patients with MSI cancers.

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