Immunoscore: a novel prognostic tool. Association with clinical outcome, response to treatment and survival in several malignancies

The predictive accuracy of the traditional staging system for cancer, the American Joint Committee on Cancer/Union Internationale Centre le Cancer (AJCC/UICC) classification of malignant tumors, is based on disease progression as a tumor cell-autonomous process, regardless the effects of the host immune response. The natural history of a tumor includes different phases of growth, migration and invasion. During these phases, tumor cells interact with their microenvironment and are influenced by signals from stromal, endothelial, inflammatory and immune cells. Indeed, tumors are often infiltrated by defensive cells such as lymphocytes, macrophages or mast cells and it has been shown extensively that lymphocytes may control cancer outcome, as evidenced in several human malignancies. Increasing evidence suggests that cancer progression is strongly influenced by host immune response, which is represented by immune cell infiltrates. The T-lymphocyte-based immunoscore (IS) has proved to be a prognostic factor in human malignancies such as colon, pancreas and lung cancer, hepatocellular carcinoma, melanoma and even brain metastases. Although the IS was initially established to evaluate the prognosis of stage I/II/III colon cancer patients, its association with clinical outcomes and survival has been shown in other malignancies. The aim of this review is to analyze the association of IS with prognosis, survival and response to therapy in different tumor types.