Is immunity in cancer the key to improving clinical outcome?: Report on the International Symposium on Immunotherapy, The Royal Society, London, UK, 12–13 May 2017

The central importance of the immune system in the natural history of cancer control and progression is now clearly established. It can prevent growth and kill the cancer cells, but also facilitate tumour progression through selection of the most fit cells to survive in an immunocompetent host or through altering the local microenvironment that promotes tumour outgrowth.1 Immunotherapy (IM) has now been clinically validated as an effective treatment for many cancers. The important breakthroughs were led by the impressive impact of blockade of cytotoxic T-lymphocyte-associated antigen 4 (CTLA-4) or programmed cell death protein 1 (PD1) on survival of a proportion of patients with, for example, metastatic melanoma or non-small-cell lung cancer, which were previously relatively refractory to existing treatments.2 However, objective tumour responses are only seen in a fraction of patients across different malignancies; many do not benefit at all and there can be significant toxicities. Numerous strategies are currently being evaluated both preclinically and clinically to better understand and combat the immune-suppressive factors significantly limiting patient response to therapy.3 IM has usually been considered as an alternative to more traditional modalities. Previously the view has been that chemotherapy is inherently immunosuppressive and not suitable for combining with IM. These generalizations are being challenged by a new paradigm whereby immune surveillance is the agent that improves and even cures some patients with cancer, even those treated by conventional radio- or chemotherapy.