Exciting advances in immunotherapy research over the last decade have revolutionized cancer therapy. However, significant gaps remain in our understanding of systemic immune responses in cancer, limiting patient benefit. In this webinar, Breanna Allen will highlight recent efforts to define organism-wide immune landscapes in response to tumor development. Data from various mouse tumor models and studies of cancer patients reveal remarkable plasticity in the systemic immune state compared to the tumor microenvironment, and demonstrate that tumor development dynamically reshapes the composition and function of the immune macroenvironment.