Monocyte-to-lymphocyte ratio as a prognostic factor in peripheral whole blood samples of colorectal cancer patients

BACKGROUND: Colorectal cancer is the third most common malignancy worldwide. Therefore, it is critically important to identify new useful markers that can be easily obtained in routine practice. Inflammation is a crucial issue in the pathogenesis and development of cancer. AIM: To evaluate the prognostic value of absolute monocyte count, monocyte to lymphocyte ratio (MLR), the combination of neutrophil-to-lymphocyte ratio and platelet-to-lymphocyte ratio (NLR-PLR), and combined platelet and neutrophil-to-lymphocyte ratio (PLT-NLR) in peripheral blood samples of patients with colorectal cancer undergoing surgery. METHODS: We conducted a retrospective study of 160 patients with colorectal cancer who underwent surgery, and 42 healthy controls. The status of absolute monocyte count, MLR, NLR-PLR and PLT-NLR was calculated on the basis of blood samples obtained before and after surgery. Haematologic factors were examined in correlation with the type of tumour growth, tumour size, histological type, percentage of mucinous component, grade of malignancy, Tumour-Node-Metastasis stage, venous, lymphatic and perineural invasion of cancer cells, status of lymph node invasion and the presence of cancer cell deposits. The Kaplan-Meier method and the long-rank test were used to compare survival curves. To determine independent prognostic factors, univariate and multivariate Cox proportional hazards regression models were applied. RESULTS: The PLT-NLR status was correlated with tumour size and the presence of perineural invasion (P = 0.015; P = -0.174, P = 0.037). Moreover, high NLR-PLR and PLR-NLR ratios in the blood samples obtained after surgery were positively associated with histological type of cancer and percentage of the mucinous component (NLR-PLR: P = 0.002; P = 0.009; PLR-NLR status: P = 0.002; P = 0.007). The analysis of 5-year disease-free survival showed that the MLR of whole blood obtained after surgery [HR = 2.903, 95%CI: (1.368-6.158), P = 0.005] and the status of lymph node metastasis [HR = 0.813, 95%CI: (0.653-1.013), P = 0.050] were independent prognostic factors in colorectal cancer patients. CONCLUSION: The postoperative MLR in whole blood samples can be used as an independent prognostic factor in patients diagnosed with colorectal cancer.