The systemic inflammation-based neutrophil-lymphocyte ratio: experience in patients with cancer

There is increasing and consistent evidence that cancer-associated inflammation is a key determinant of outcome in patients with cancer. Various markers of inflammation have been examined over the past decade in an attempt to refine stratification of patients to treatment and predict survival. One routinely available marker of the systemic inflammatory response is the neutrophil-lymphocyte ratio (NLR), which is derived from the absolute neutrophil and absolute lymphocyte counts of a full blood count. To date, over 60 studies (>37,000 patients) have examined the clinical utility of the NLR to predict patient outcomes in a variety of cancers. The present systematic review examines and comments on the clinical utility of the NLR. The NLR had independent prognostic value in (a) unselected cohorts (1 study of >12,000 patients), (b) operable disease (20 studies, >4000 patients), (c) patients receiving neoadjuvant treatment and resection (5 studies, >1000 patients), (d) patients receiving chemo/radiotherapy (12 studies, >2000 patients) and (e) patients with inoperable disease (6 studies, >1200 patients). These studies originated from ten different countries, in particular UK, Japan, and China. Further, correlative studies (15 studies, >8500 patients) have shown that NLR is elevated in patients with more advanced or aggressive disease evidenced by increased tumour stage, nodal stage, number of metastatic lesions and as such these patients may represent a particularly high-risk patient population. Further studies investigating the tumour and host-derived factors regulating the systemic inflammatory response, in particular the NLR, may identify novel treatment strategies for patients with cancer.