Colorectal cancer (CRC) is responsible for 10% of the world-wide cancer incidence and mortality (1). Due to its significant burden on health, it is important to understand its etiological and biological behavior which may enable the improvement of the therapeutic approach towards this disease (1). Recent data have shown that primary tumor location (PTL) has prognostic and predictive implications. That is because clinical, molecular and embryological differences exist between tumors arising from different regions of the colon (2-5). These differing molecular characteristics actually translate into a differential clinical outcome with the right colon displaying a markedly worse prognosis (2,6-14). Besides its prognostic relevance, several retrospective analyses suggest that PTL may also be predictive of treatment benefit from targeted therapy with anti-EGFR targeted agents.(6-10)

   Several studies described the role of microRNA expression in the initiation and progression of CRC and its response to different therapeutic strategies (1). Other studies have shown that systemic inflammation is a key determinant role of  clinico-pathological outcomes in patients with CRC (11). As a result, the Glasgow Prognostic Score (GPS) has emerged as a prognostic indicator in cancer patients (18). However, the GPS depends only on two factors, the C-reactive protein (CRP) and the albumin (12). Consequently, many studies have investigated the predictive and prognostic role of other inflammatory markers, such as leucocyte ratios, fibrinogen, and haptoglobin (13-16), etc. We therefore aim to evaluate the expression of selected microRNA and inflammatory markers in patients with stage IV colorectal cancer and assess their correlation with tumor location, survival rates, response to systemic chemotherapy and other clinic-pathological parameters. We believe that identifying a predictive and prognostic panel made up of circulating microRNA and inflammatory markers may perhaps explain the difference in outcome between right and left colon and perhaps impact the clinical practice in patients with stage IV colorectal cancer.