Risk Factors for Lymph Node Metastasis and Recurrence in T1 Colorectal Cancer: Analysis of 801 Patients in a Single Institute

Objective To identify risk factors for lymph node metastasis and postoperative recurrence of pT1 colorectal cancer by clinicopathological study of surgically resected cases. Methods In 801 patients with pT1 colorectal cancer who underwent surgical resection with lymph node dissection between April 2007 and January 2021, we evaluated clinicopathological factors (age, gender, BMI, serum CEA level, tumor localization, additional resection after endoscopic treatment, operation time, blood loss, histological type, tumor size, vascular invasion, and central lymph node dissection). We performed univariate and multivariate analyses to examine risk factors for lymph node metastasis. We also examined risk factors for recurrence in 583 patients up to December 2017. Results Lymph node metastasis was observed in 100/801 patients (12.5%). Multivariate analysis of lymph node metastasis showed that patients with positive lymphatic invasion (odds ratio 2.57, 95% CI 1.62-4.04, P < .0001), positive venous invasion (odds ratio 2.31, 95% CI 1.48-3.61, P = .0002), and histologically poorly differentiated type (odds ratio 4.54, 95% CI 1.35-15.2, P = .014) were identified as risk factors. Postoperative recurrence was observed in 18/580 patients (3.1%). Risk factors for postoperative recurrence were also examined, including preoperative endoscopic treatment (odds ratio 3.59, 95% CI 1.18-10.9, P = .024), positive venous invasion (odds ratio 3.63, 95% CI 1.22-10.8, P = .021), positive lymph node metastasis (odds ratio 4.91, 95% CI 1.10-21.8, P = .037) were extracted as risk factors. Discussion In this study, venous invasion, lymphatic invasion, and histologically poorly differentiated type were identified as risk factors for lymph node metastasis in T1 colorectal cancer, and positive venous invasion, positive lymph node metastasis, and preoperative endoscopic treatment were identified as risk factors for recurrence. We hope that large prospective study will lead to the development of a more specific treatment strategy, including endoscopic treatment and additional surgical resection.