Radiation therapy is one of the main options in cancer treatments, alongside surgery and chemotherapy. Its efficacy largely depends on the absorbed radiation dose of the tumor cells. However, the irradiation of healthy cells results in negative side effects for the patient. Therefore, a big challenge in radiation therapy is to irradiate the tumor with sufficient dose, while keeping the irradiation of the healthy tissue reasonably low. Currently, the radiation treatment is planned by defining a volume enclosing the tumor, but with added margins to account for any uncertainties. These margins ensure that the tumor receives the prescribed dose.