Nomogram as a novel predictive tool for lymph node metastasis in T1 colorectal cancer treated with endoscopic resection: a nationwide, multicenter study

Since 2009, the Japanese Society for Cancer of the Colon and Rectum (JSCCR) guidelines have been recommending tumor budding and submucosal invasion depth, in addition to lymphovascular invasion and tumor grade, to be included as risk factors for lymph node metastasis (LNM) in T1 colorectal carcinoma (CRC) patients. In this study, a novel nomogram was developed and validated using large-scale real-world data, including the JSCCR risk factors, to accurately evaluate the risk of LNM in T1 CRC.Data from 4,673 T1 CRC patients treated at 27 high-volume institutions between 2009 and 2016 were analyzed for LNM risk. To prepare a nonrandom split sample, the total cohort was divided into development and validation cohorts. Pathological findings were extracted from the medical records of each participating institution. The discrimination ability was measured using the concordance index, and the variability in each prediction was evaluated using calibration curves.Six independent risk factors for LNM, including submucosal invasion depth and tumor budding, were identified in the development cohort and entered into a nomogram. The concordance index was 0.784 for the clinical calculator in the development cohort and 0.790 in the validation cohort. The calibration curve approached the 45-degree diagonal in the validation cohort.This is the first nomogram to include submucosal invasion depth and tumor budding for use in routine pathological diagnosis based on data from a nationwide multi-institutional study. With this nomogram developed with real-world data decision-making for an appropriate treatment strategy for T1 CRC should improve.