Research in context
Evidence before this study
We searched MEDLINE via PubMed for evidence available by Jan 1, 2018, for an association between immune cell infiltrates of tumours and prognosis in various cancer types. 250 published articles implicating cytotoxic T cells, memory T cells, and T-helper cell subpopulations in prognosis of cancer patients were retrieved (28 different cancer types were analysed). Tumour infiltration by cytotoxic CD8+ T cells was associated with a good prognosis in 98% of the studies. By contrast, other T-helper subpopulations had a good or a bad prognostic effect depending on the method used and on the cancer types. Colorectal cancer was the most studied cancer type. The quantification of immune infiltrates had a prognostic importance superior to that of the American Joint Committee on Cancer (AJCC) and Union for International Cancer Control (UICC) TNM classification system. Multiple ways to classify cancer, colorectal cancer in particular, have been proposed. These rely on tumour cell characteristics, such as morphology, molecular pathways, mutation status, tumour cell origin, and tumour gene expression. Despite the importance of the intratumour immune reaction to predict patients at high risk and low risk of recurrence and death, no immune marker is used in the classification of colorectal cancer at present.
Added value of this study
After the first World Immunotherapy Council meeting on Feb 21–24, 2012, bringing together 17 cancer international organisations, a decision was made, together with the Society for Immunotherapy of Cancer, to initiate an international Immunoscore consortium to assess the prognostic value of total T-lymphocyte and cytotoxic T-lymphocyte tumour infiltrate. The international Immunoscore consortium of expert pathologists and immunologists identified a strategy for an international multicentre study to validate the consensus Immunoscore in patients with stage I–III colon cancer. The purpose of the study was to agree on how to harmonise the Immunoscore assay, to demonstrate the feasibility and reproducibility of the Immunoscore, to demonstrate the utility of the Immunoscore to predict patients with stage II colon cancer at high risk of recurrence, and to validate the prognostic value of the Immunoscore in routine clinical settings.
Implications of all the available evidence
Compared with existing prognostic tools, the consensus Immunoscore can be used to better define the prognosis of cancer patients, better identify patients at high risk of tumour recurrence (including patients with stage II colon cancer), and stratify patients who could benefit from adjuvant therapies. The consensus Immunoscore study represents the largest international consortium validating a standardised immune parameter to stratify patients with cancer. The Immunoscore had a prognostic value superior to that of existing tumour parameters. This initiative and these results support the implementation of the consensus Immunoscore as a new component for a TNM-Immune classification of cancer.