Primary tumour immune response and lymph node yields in colon cancer

BACKGROUND: The mechanism underlying improved survival in non-metastatic colon cancer with higher lymph node (LN) yield is unknown. This study aimed to identify whether molecular features in the primary tumour were predictive of LN yield. METHODS: Clinical, genomic, transcriptomic, proteomic and methylation data of non-metastatic, colon cancers studied in The Cancer Genome Atlas were interrogated for associations with LN yield. Based on maximal survival effects, patients were segregated into high (>15) and low (≤15) LN yield. Gene set enrichment analysis was performed on transcriptomic changes to identify biological processes associated with LN yield. Correlations were validated in an independent set of Stage II colon cancers. RESULTS: High LN yield was found predictive of overall and disease-free survival. There was no association of higher LN yield and increasing nodal positivity. High LN yield was strongly linked with gene expression changes associated with the adaptive and dendritic cell immune response. This association was most prominent in node-negative cancers. Analogous findings were reproduced in the validation dataset. CONCLUSION: The study shows a strong association of an activated immune response in tumours with a high LN yield. Immunogenic tumours have a better prognosis, likely explaining the survival benefit with higher LN yields.