This Master. thesis is based on the following paper: A mathematical model of tumour growth with Beddington–DeAngelis functional response: a case of cancer without disease. Cancer has become a leading cause of death worldwide. Cancer cells grow rapidly and have the ability to metastasize to other organs. The goal of cancer treatments is to destroy cancer cells without damage to healthy cells. Chemotherapy and immunotherapy are among the most common options for cancer treatment. Chemotherapy is the use of drugs to destroy cancer cells, and immunotherapy is a treatment that enhances the immune system in fighting cancer. Unfortunately, chemotherapy destroys not only the cancer cells but also the surrounding healthy cells; additionally, more effective drugs are likely to be more toxic. Immunotherapy has been shown to be ineffective in patients with solid tumours or advanced cancer.