Immunotherapy has revolutionized the treatment of many cancers, with some patients previously considered incurable, now living long years. BUT the benefit varies enormously depending on the cancer, indication and tumour molecular make-up. Also, immunotherapy can have lifelong and even fatal toxicities, and it’s expensive. I will run through a summary of what immunotherapy entails, when it works, doesn’t work, and might work, mainly in colorectal cancer (see talks earlier in the day for upper GI cancer immunotherapy), and the difficulty in weighing the risks and benefits.