Immuno-oncology of Dormant Tumours

Cancer is a complex, often aggressive disease. As such, cancer treatment requires a diverse approach that often includes surgery, chemotherapy, radiotherapy, targeted therapy, or immunotherapy. Despite the potency of these treatments, cancer cells adapt to escape killing and survive either in their original microenvironmental niche, or as disseminated cancer cells in distant organs. Depending on tumour type and treatment modality, tumours display a variety of growth patterns, from rapid proliferation and invasion to a more controlled dormant phenotype. This dormant phenotype is characterized clinically as the asymptomatic period post therapy before relapse, and biologically by an enrichment in cancer cells that are not dividing but survive in a quiescent state, arrested in G0-G1 phase of cell cycle. Dormancy is a tumour intrinsic characteristic that corresponds to the equilibrium phase of the immune-editing hypothesis, in which tumour cells neither proliferate nor are eliminated by the immune response. In this chapter we provide an overview of anti-tumour immunity and ways in which the immune response may shape tumour dormancy.