Prognostic value of multiple cytokine analysis in colorectal cancer: a systematic review

The link between inflammation and outcome has been established in colorectal cancer through experimental evidence demonstrating an influential role of pro-inflammatory cytokines on tumour growth and progression. Furthermore, prognostic scores based on overall markers of systemic inflammation such as C-reactive protein and neutrophil count have been validated. Over recent years, an increasing number of inflammatory cytokines have been identified as prognostic predictors in colorectal cancer and the aim of this review was to evaluate the literature on the prognostic value of multiple cytokine measurement. The English language literature published since the year 2000 was searched using terms including, 'colorectal cancer', 'cytokines' and 'prognosis' through Medline, Embase and Scopus databases. Reports were screened by two independent reviewers and studies evaluating fewer than three cytokines were excluded. Quality assessments were performed in six domains before data extraction was undertaken in duplicate. Seven studies were found to evaluate multiple cytokines after 570 records were screened. The quality of these studies ranged from poor to moderate and were heterogeneous in terms of the patient population and the number and selection of cytokines tested. Four studies combined multiple cytokine levels into a single score and found them to be predictive of prognosis whereas the association between individual cytokines and outcome was not demonstrated consistently. The combination of multiple cytokine markers into a single prognostic score shows promise in colorectal cancer and further research is required to establish and validate such a score.