[Comment] Long-term prognostic outcomes in high-risk T1 colorectal cancer: a multicentre retrospective comparison of surgery versus observation postendoscopic treatment

[Aim] The risk of lymph node metastasis after endoscopic resection of high-risk T1 colorectal cancer prompts additional resection. However, age and comorbidities are considered in decision-making and some surgeons opt for observation. We compared the long-term outcomes of these approaches with the aim of clarifying the need for additional resection. [Method] This multicentre retrospective study included high-risk T1 colorectal cancer patients treated with endoscopic submucosal dissection (ESD) between January 2013 and April 2021. Patients who met one or more of the following criteria were eligible for inclusion: submucosal invasion depth ≥ 1,000 μm, vessel invasion, poor differentiation, budding grade 2/3 or a positive vertical margin. Patients were divided into resection (R) and observation (O) groups. Outcomes were evaluated based on overall survival (OS) and 5-year cancer-specific survival (CSS), with an additional stratified analysis using the age-adjusted Charlson comorbidity index (ACCI). [Results] The study included 178 patients (group R, n=131; group O, n=47). Patients in group O were significantly older and had more comorbidities. Group R showed better 5-year OS and CSS (OS, 87.0% vs. 58.9%, P=0.001; CSS, 98.8% vs. 78.4%, P=0.002). Stratification by ACCI revealed that benefits of additional resection remained for patients with ACCI ≤ 6 (OS, 91.2% vs. 58.3%, P=0.013; CSS, 98.4% vs.61.7%, P<0.001) but not for those with ACCI ≥ 7 (OS, 75.9% vs. 59.8%, P=0.289; CSS, 100% vs. 100%, P=0.617). [Conclusions] Significant survival benefits were demonstrated in group R patients with high-risk T1 cancer. However, the survival benefit of additional surgical resection was unconfirmed in patients with ACCI ≥ 7.