Subpopulation analysis of survival in high-risk T1 colorectal cancer: surgery versus endoscopic resection only

Background and Aims: This study aimed to assess the long-term survival of patients with T1 colorectal cancer (CRC) after local or surgical resection considering the type and number of risk factors for lymph node metastasis. Methods: This study included patients with high-risk T1 CRC who underwent therapeutic resection at the Na-tional Cancer Center, Korea between January 2001 and December 2014. Risk factors included positive resection margin, high-grade histology, deep submucosal invasion, vascular invasion, budding, and no background adenoma (BGA). We statistically divided the population into favorable or unfavorable subpopulations. The favorable subpopulation included the following 5 combinations of risk factors: positive margin only or uncon-ditional for margin status, deep submucosal invasion only, budding only, no BGA only, and budding + no BGA. We analyzed the survival rate according to the resection type (local or surgical) in the total cohort and in each subpopulation. Results: Eighty-one and 466 patients underwent local and surgical resections, respectively. The distant recurrence-free survival (DRFS) and overall survival (OS) rates were significantly high in the surgical group (haz-ard ratio [HR], .20; 95% confidence interval [CI], .06-.61; P = .0045 and HR, .41; 95% CI, .25-.70; P = .0010, respectively). In the favorable subpopulation, both DRFS and OS rates were not significantly different between the surgical and local groups (HR, .26; 95% CI, .02-4.19; P = .3431 and HR, .58; 95% CI, .27-1.23; P = .1534, respectively). Conclusions: Intensive surveillance without additional surgery may be another option in selected cases after of high-risk T1 CRC endoscopic resection.