pT1 Colorectal Cancer Detected in a Colorectal Cancer Mass Screening Program: Treatment and Factors Associated with Residual and Extraluminal Disease.

The aim of this study is to describe the treatment of pT1 colorectal cancer (CRC) in a mass screening program, the surgery-related complications and the factors associated with residual disease after endoscopic resection and extraluminal disease after surgery. We included in this retrospective analysis all the pT1 CRC detected in the Galician CRC screening program between May 2013 and June 2019. We determined which variables were independently associated with the outcomes of the study through a multivariable logistic regression analysis. We included 370-354 pT1 N0(X), 16 pT1N1- out of the 971 CRC detected; 277 (74.9%) were resected endoscopically and 162 (43.8%) were not referred to surgery. There were surgical complications in 30.7% and 16.3% of the patients during hospitalization and after discharge. Residual disease was detected in 12 (4.3%) after endoscopic resection and extraluminal disease in 18 (8.6%) patients after surgery. The variables independently associated with initial endoscopic resection were a pedunculated morphology (OR 33.1, 95% CI 4.3-254), a diameter ≥ 20 mm (OR 3.94, 95% CI 1.39-11.18) and a Site-Morphology-Size-Access score < 9 (OR 428, 95% CI 42-4263). The variables related with surgery rescue were a piecemeal resection (OR 4.48, 95% CI 1.48-13.6), an infiltrated/nonevaluable resection border (OR 7.44, 95% CI 2.12-26.0), a non-well-differentiated histology (OR 4.76, 95% CI 1.07-20.0), vascular infiltration (OR 8.24, 95% CI 2.72-25.0) and a Haggitt 4 infiltration of the submucosa (OR 5.68, 95% CI 2.62-12.3). Residual disease after endoscopic resection was associated with an infiltrated/nonevaluable resection border (OR 34.9, 95% CI 4.08-298), a non-well-differentiated histology (OR 6.67, 95% CI 1.05-50.0), and the vascular infiltration of the submucosa (OR 7.61, 95% CI 1.55-37.4). The variables related with extraluminal disease after surgical resection were no endoscopic resection (OR 4.34, 95% CI 1.26-14.28), a non-well-differentiated histology (OR 4.35, 95% CI 1.39-14.29) and the lymphatic infiltration of the submucosa (OR 4.8, 95% CI 1.32-17.8). In a CRC screening program, although most of pT1 CRC are candidates for endoscopic treatment, surgery is a safe procedure. We have defined some easy to evaluate variables that can be used in the decision-making process.