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

Background and Aims: Since 2009, the Japanese Society for Cancer of the Colon and Rectum guidelines have recommended that tumor budding and submucosal invasion depth, in addition to lymphovascular invasion and tumor grade, be included as risk factors for lymph node metastasis (LNM) in patients with T1 colorectal cancer (CRC). In this study, a novel nomogram was developed and validated by usirge-scale, real-world data, including the Japanese Society for Cancer of the Colon and Rectum risk factors, to accurately evaluate the risk of LNM in T1 CRC. Methods: Data from 4673 patients with T1 CRC 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. Pathologic findings were extracted from the medical records of each participating institu-tion. The discrimination ability was measured by using the concordance index, and the variability in each predic-tion was evaluated by using calibration curves. Results: 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 .784 for the clin-ical calculator in the development cohort and .790 in the validation cohort. The calibration curve approached the 45-degree diagonal in the validation cohort. Conclusions: This is the first nomogram to include submucosal invasion depth and tumor budding for use in routine pathologic diagnosis based on data from a nationwide multi-institutional study. This nomogram, devel-oped with real-world data, should improve decision-making for an appropriate treatment strategy for T1 CRC.