Multi-scale modeling of cancer growth and treatment response would allow better understanding of the different biophysical and biochemical interactions at the molecular, cellular, tissue, and organ levels. Different mathematical models ranging from continuum, discrete, to hybrid have been proposed and evaluated in different theoretical and experimental settings. These process models not only can help explain the complex tumor-treatment system but can also be used to personalize treatment single or combined modality regimens and predict their efficacy. In this chapter, we will present examples of such modeling approaches and discuss its ability in the cases of chemotherapy drugs and immunotherapy agents.