Colorectal cancer (CRC) is the third most common cancer worldwide. While the incidence and the mortality rate of colorectal cancer has decreased due to effective cancer screening, CRC is still the second most common cause of cancer-related deaths in the Western world (1) and 20% of patients with CRC have metastases at time of diagnosis (2).
Advances in CRC therapy as combination of chemotherapy with targeted agents and supportive care have led to significant improvement in survival rates for CRC patients. However, metastatic colorectal cancer (mCRC) remains to have poor prognosis with with an approximately 2-year survival (3).
A multitude of factors at diagnosis, including clinical parameters (age, performance status, comorbidities), biological properties of the tumor (local growth, distant metastasis, sidedness), molecular factors (KRAS, NRAS, and BRAF mutations) and biochemical markers such as carcinoembryonic antigen, lactate dehydrogenase, platelets, leucocytes, hemoglobin, alkaline phosphatase, albumin have important prognostic impact for outcome in mCRC (4,5). In recent decades, studies provided definitive evidence about the association between inflammation and cancer development (6,7).
The inflammation is essential for tumor microenvironment, and inflammatory cells can affect tumor proliferation, angiogenesis, metastasis, and genetic instability. Lymphocytes, macrophages, and granulocytes are involved in the anti-cancer battle (8). The main cell population in anti-cancer immune response is the population of cytotoxic T lymphocytes (CTLs) (9). Neutrophils may play a crucial role in inflammation driven tumorigenesis (10). Neutrophil population consists of pro- and antitumor subpopulations (11). It is controversy that neutrophil abundance correlates with a better prognosis. (12). Platelets release some tumor growth factors which play a significant role in cancer growth, progression, and metastasizing (13). In previous studies, elevated pretreatment neutrophil-to-lymphocyte ratio (NLR) and platelet-to-lymphocyte ratio (PLR) in peripheral blood were identified as independent prognostic factors. As a result, various studies have suggested that analysis of inflammatory factors could be helpful for predicting survival in cancer, including assessment of inflammatory cells in peripheral blood.
Fortunately, several parameters for predicting survival in patients with CRC have been identified, including such inflammatory-based prognostic parameters as NLR, PLR, white blood cell count, and platelet count (14,15).
NLR, calculated as neutrophil count divided by lymphocyte count, is the most frequently reported marker and is used in almost every stage of CRC (14,16,17). Increased NLR is associated with worse outcomes and poor response to adjuvant chemotherapy or radiotherapy (18, 19). PLR, defined as platelet count divided by lymphocyte count, is also gaining attention in some research (20). It is contradictory whether both indices are associated with first line chemotherapy response in patients with metastatic colorectal disease. Here, we present real-life data about the association of NLR and PLR with survival outcomes in patients with mCRC.