The goal is to develop a novel mathematical model and computer simulation environment to realistically predict the behavior of recurrent tumors undergoing combined-hyperthermia-radiotherapy (CHR) treatment. This type of treatment uses both heat and radiation to treat different types of cancer. For instance, when a tumor is heated, the effects of radiation on tumor tissue are enhanced. This creates a type of feedback, in which differences in temperature and heating time improve the performance of the radiotherapy. Current tools do not incorporate such feedback effect into their model and are therefore less realistic. We aim to couple three interdependent models: (i) the first model represents how heat affects tumor temperature and its properties with respect to radiation; (ii) the second model estimates the amount of radiation energy deposited in the tumor according to its temperature; (iii) the third model addresses the tumor's combined response to both heating and exposure to ionizing radiation.