Cancer can be seen as an evolutionary disease, where natural selectionworks on the cells in an organism to promote traits that are detrimental tothe organism. Evolutionary game theory (EGT) is a ﬁeld using the methodsof game theory, which is usually concerned with the behaviour of rationalagents, to model adaptive systems. The basis for EGT is that the stable restpoints of the adaptive system correspond to stable equilibrium solutions torelated games.EGT has been used to model the cellular evolution in cancer with focuson the interactions between different cancer cells, and between cancercells and normal cells. This thesis is an attempt to model the relationshipbetween the host and the cancer cells using game theory.Simpliﬁed systems of differential equations simultaneously describingthe cellular evolution within organisms as well as organismal evolutionare presented, and a correspondence between stable rest points of thesesystems and stable equilibrium solutions to a class of extensive games areshown.The game theoretical models are applied to modiﬁed versions of cell-cell interaction games from the literature. The results show that it isevolutionarily plausible for multicellular organisms to develop tacticalelements in their anti-cancer strategies.