In cancer cells, the administration of drugs, such as TRAIL, can induce a mode of cell death (apoptosis). This applied reagent shifts the cell's internal inhibition and activation reactions towards the activation of caspases, triggering the cell death. In this contribution, a macroscopic model in the framework of the well-known Theory of Porous Media is introduced to model the apoptosis reaction for lung-cancer metastases located in brain tissue. Therein, the density-production terms describe the apoptosis via a set of ordinary differential equations. The model is adapted to apoptosis experiments, measuring the survival rate of lung-cancer cells in dependency of the TRAIL concentration. Thereby, the model is compared to a reduced model version using a constitutive logarithmic apoptosis function within the production terms.