RADIOTHERAPY. RADIOTHERAPY Radiotherapy Department of the Gustave Roussy Institute, in the French region of Ile-de-France. Cancer treatment. Radiotherapy is one of the most important treatments against brain tumors. A noninvasive, ´bloodless´ surgical procedure, it delivers focused radiation to the cancerous area in order to destroy or inhibit the growth of abnormal cells while minimizing the amount of radiation affecting nearby structures. Here, on screen, the linear accelerator, simulation