Both types of therapy aim to block the growth of the tumour cells and eventually destroy them. The main difference is that the drugs administered during chemotherapy affect the entire body, whereas with radiotherapy, the ionising radiation only affects the tissue that it is applied to Furthermore, the effectiveness of the radiotherapy is much greater in the treated area than in the surrounding tissues and it can destroy significantly more tumour cells in the affected area. That’s why these two methods of treatment are frequently combined.
Often the aim of chemotherapy is also to eliminate any possible but not yet visible micrometastases in the body. Whereas radiotherapy can be used where tumour cells are grouped together in larger nodes or structures and where chemotherapy alone would not generally be sufficiently effective. In addition, the medication used in chemotherapy often makes the rapidly dividing tumour cells more sensitive to the ionising radiation, thereby increasing the effectiveness of the radiation therapy.