Lymph node metastasis in T1 colorectal cancer: Risk factors and prediction model.

Endoscopic resection is typically performed for early T1 stage colorectal cancer (T1 CRC). Additional surgery is subsequently recommended based on pathological findings; however, the current criteria may result in overtreatment. The present study aimed to re-examine the reported risk factors for lymph node (LN) metastasis in T1 CRC and develop a prediction model using a large multi-institutional dataset. In this retrospective study, the medical records of 1,185 patients with T1 CRC who underwent surgery between January 2008 and December 2020 were investigated. Slides pathologically re-assessable for additional risk factors were re-examined. A total of 251 patients with inadequate data were excluded, and 934 patients were randomly assigned at a ratio of 3:1 to the training and validation datasets. In the univariate analysis, left-sided CRC (P=0.003), deep submucosal invasion depth (P=0.005), poor histological grade (P=0.020), lymphatic invasion (P<0.001), venous invasion (P<0.001) and tumor budding grade 2/3 (P<0.001) were significant risk factors for LN metastasis. A nomogram predicting LN metastasis was developed using these variables, with an area under the received operating characteristic curve (AUC) of 0.786. The nomogram was validated using a validation set with an AUC of 0.721, indicating moderate accuracy. No LN metastases were observed in patients with <90 points using the nomogram; therefore, patients with a low nomogram score may avoid undergoing surgical resection. Prediction of LN metastasis using this developed nomogram may help identify patients who are at high-risk who require surgery.