Though endoscopic treatment is an option for T1 colorectal cancer (CRC), the optimal indications and long-term outcomes of this strategy need to be validated. Therefore, the aim of this study is to investigate long-term outcomes of endoscopy versus surgery and optimal indications for endoscopic treatment of T1 CRC. This retrospective study included 428 T1 CRC patients treated with initial endoscopy (n=224) or surgery (n=204) at Severance Hospital between 2005 and 2012. Patients were subdivided into 4 groups according to conventional indications (CIs) for endoscopic treatment: negative lateral/vertical margins; submucosal invasion depth within 1000mm; no lymphovascular invasion (LVI); well or moderately differentiated. For prognosis evaluation, short-term outcomes (resection margin and complications) and long-term outcomes (recurrence and cancer-specific mortality) were evaluated. Endoscopic treatment achieved en bloc resection in 86.6% of 224 patients. Recurrence and mortality did not differ between the endoscopy and surgery groups with or without CIs. For patients with CIs, although 80 patients were treated endoscopically with 1 (1.3%) recurrence and 0 mortality, 75 patients were treated surgically with 2 (2.7%) recurrence and 1 (1.3%) mortality. Multivariate analysis revealed that LVI positivity and poorly differentiated histology were independently associated with lymph node metastasis (LNM; P<0.001 and P=0.001, respectively). To determine whether the depth of submucosal invasion among criteria of CIs could be extended for endoscopic treatment, LNM was analyzed by extending the depth of submucosal invasion. There was no LNM in 155 patients within conventional indication. When the depth of submucosal invasion was extended up to 1500mm, LNM was occurred (1/197 patient [0.5%]). In addition, when the depth of submucosal invasion was extended up to 2000mm, LNM was increased (4/271 patient [1.5%]). Endoscopic treatment is safe, effective, and is associated with favorable long-term outcomes compared to surgery for initial treatment of T1 CRC patients with CIs. However, the risk of LNM makes it unsafe to extend the CIs for endoscopic therapy in these patients.
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