BACKGROUND AND OBJECTIVES: The detection of a simple and reliable prognostic biomarker for colorectal cancer (CRC) outcomes remains a significant challenge. The use of neutrophil-to-lymphocyte ratio (NLR), has been reported to predict surgical and survival outcomes. The aim of our review was to assess the predictive value of pre-operative NLR in predicting post-operative outcomes in CRC.METHODS: Asystematic review of the available studies on NLR in CRC was performed. Primarily, we assessed its ability to predict survival outcomes, and highlight values that would help adjuvant therapy choices.RESULTS: 19 studies comprising 10 259 patients were included. Eleven and eight studies reported on patients with localized CRC and colorectal liver metastasis, respectively. Five-year survival for those with localized CRC was 77.2% in patients with a "low" pre-operative NLR versus 50.8% in those with a "high" pre-operative NLR value. Alternatively, for patients with colorectal liver metastasis, patients with a "high" pre-operative NLR value had a 5-year survival of 27%.CONCLUSION: Elevated pre-operative NLR>5 is associated with poorer long-term survival in both patients with localized CRC and those with liver metastasis. NLR is a useful biomarker in delineating those patients with poorer prognosis and whom may benefit from adjuvant therapies.