The expanding landscape of immunotherapy in colorectal cancer

Abstract Since the first immune checkpoint inhibitor was approved for clinical use in metastatic melanoma in 2011, immunotherapy treatments have revolutionized the treatment landscape in a wide range of solid tumour types, most notably melanoma, non-small cell lung cancer (NSCLC) and renal cell cancer. This novel approach to systemic treatment, after many years of conventional chemotherapy-based approaches, rapidly became the focus of a wealth of clinical research. Through greater understanding of the immune system and its role in colorectal cancer, particularly in patients harbouring mismatch repair-deficient tumours, immunotherapy has now also been translated into colorectal cancer therapeutics. The next big question will be how we can use immunotherapy effectively to also target the other 95% of metastatic colorectal cancer that is not mismatch repair deficient.