Delay Differential Model for Tumour-Immune Response with Chemoimmunotherapy and Optimal Control
Figure 2
(a) shows the regions of existence of coexisting equilibria of model (3) in -plane with the parameter values , , , , , , , , and . The dark blue region (0) represents the case where there is no equilibrium, the light blue regions (1a, 1b) represent the case where there is a unique equilibrium, the orange region (2) represents the case where there are two steady states, and the brown region (3) represents the case where there is three equilibria. (b) shows the nullclines of the model which has up to four steady states: tumour-free steady state “”; tumour dormancy steady state “”; medium concentration tumour steady state “”; and escape tumour steady state “.”
