The Emerging Role of Neutrophil to Lymphocyte Ratio in Determining Colorectal Cancer Treatment Outcomes: A Systematic Review and Meta-Analysis

There is growing evidence suggesting that the neutrophil to lymphocyte ratio (NLR) can act as an independent predictor of long-term outcomes in patients undergoing treatment for colorectal cancer (CRC). This study aims to systematically review the role of NLR in predicting survival for patients with CRC undergoing treatments, and to evaluate its utility within a CRC surveillance program. This meta-analysis was performed according to PRISMA guidelines. Outcomes of interest included disease-free survival (DFS) for patients undergoing treatment with curative intent and progression-free survival (PFS) in patients undergoing treatments with palliative intent. Thirteen observational cohort studies published from 2007 to 2013 evaluated the role of NLR as a predictor of outcome following treatment for CRC. These included (i) patients undergoing surgery to resect the primary cancer (seven studies); (ii) those undergoing palliative chemotherapy (three studies); and (iii) patients undergoing potentially curative treatments for CRC liver metastases (three studies). When all studies were considered, a high pretreatment NLR independently predicted survival (HR 2.08; 95 % CI 1.64-2.64). A high NLR also predicted significantly poorer survival in each of the three groups. Finally, over a 3-year follow-up period, high NLR became a significant predictor of poor outcome at year 2 (HR 2.76; 95 % CI 2.06-3.69; p < 0.00001) and 3 (HR 2.03; 95 % CI 1.48-2.78; p < 0.0001), but not in the first year of follow-up (HR 1.47; 95 % CI 0.89-2.41; p = 0.13). Elevated preoperative NLR is associated with poorer survival in CRC patients undergoing treatment and may have a role in CRC surveillance programs as a means of delivering more personalized cancer care.