The MIMIC Study: Prognostic Role and Cutoff Definition of Monocyte-to-Lymphocyte Ratio and Lactate Dehydrogenase Levels in Metastatic Colorectal Cancer

Background: Monocyte-to-lymphocyte ratio (MLR) and lactate dehydrogenase (LDH) levels are circulating biomarkers that provide information about tumor-related inflammation and immune suppression. This study aimed to evaluate the prognostic role of MLR and LDH in metastatic colorectal cancer (mCRC).

Material and methods: This multicentric study analyzed a consecutive cohort of 528 patients with mCRC treated in 2009-2017. The whole population was randomly divided in training and validation cohort. The first was used to identify a threshold for MLR and to create the prognostic model with MLR and MLR-LDH combined (group 1: MLR-LDH low; group 2: MLR or LDH high; group 3: MLR-LDH high). The second cohort was used to validate the model.

Results: At the median follow-up of 55 months, median overall survival (OS) was 22 months. By multivariate analysis, high MLR >0.49 (hazard ratio [HR], 2.37; 95% confidence interval [C.I.], 1.39-4.04), high LDH (HR, 1.73; 95% C.I., 1.03-2.90) in the first model, group 2 (HR, 2.74; 95% C.I.; 1.62-4.66), and group 3 (HR, 3.73; 95% C.I., 1.94-7.18) in the combined model, had a worse prognosis in terms of OS. These data were confirmed both in the validation set and then in the whole cohort.

Conclusion: MLR and LDH are circulating cost-effective biomarkers, readily available in clinical practice, that can be useful for predicting the prognosis of patients with mCRC.

Implications for practice: High monocyte-to-lymphocyte ratio (MLR) and lactate dehydrogenase (LDH) levels could be a sign of a tumor's recruitment of suppressive and inflammatory cells worsening prognosis of different types of cancer, including colorectal cancer (CRC). Currently, no data are available for metastatic CRC regarding a cutoff definition for MLR or the prognostic impact of MLR and MLR-LDH combined. The present study showed in the training cohort and confirmed in the validation and whole cohort that MLR is a reliable and independent laboratory biomarker, which is easy to use, to predict clinical outcomes in patients with mCRC. Moreover, MLR and composite MLR-LDH could potentially result in an incremental improvement in the prognostic value of these biomarkers, being used as stratification tools for patients with mCRC.