Tumour deposits are associated with worse survival than extranodal extension; a network meta-analysis on tumour nodules in colorectal cancer.

Lymph node metastases (LNM) play a central role in the tumour-node-metastasis (TNM) classification for colorectal cancer (CRC), with extranodal extension (ENE) as an adverse feature. ENE has never been directly compared to tumour deposits (TD). The aim of this study was to perform an up-to-date systematic review, including a network meta-analysis to compare their prognostic value. A comprehensive search was conducted on PubMed, Embase, Web of Science and Cochrane databases to identify all prognostic studies on ENE and TD. A total of 20 studies were included, with 7719 cases. The primary outcome was 5-year disease-free survival (DFS); secondary outcomes were overall survival (OS) and disease-specific survival (DSS). Frequentist paired and network meta-analyses were performed using the netmeta package in R. For univariable DFS analysis, LNM + TD+ cases had a significantly worse outcome compared with LNM + ENE+ cases [hazard ratio (HR) = 1.27, 95% confidence interval (CI) = 1.06-1.53], which was no longer significant for multivariable DFS analysis (HR = 1.13, 95% CI = 0.87-1.46). All OS and multivariable DSS analyses showed a significantly worse outcome for LNM + TD+ cases compared with LNM + ENE cases. For all outcomes, both LNM + TD+ and LNM + ENE+ had a significantly increased hazard compared with LNM+ cases. This study shows that there is a trend towards worse outcome for LNM + TD+ than LNM + ENE+, not statistically significant in multivariable DFS analysis. Both groups perform significantly worse than cases with LNM only. To improve the accuracy of CRC staging, we recommend to put more emphasis on both ENE and TD in the TNM classification, with the most prominent role for TD.