• External radiotherapy is the most frequent form. It involves delivering an electron, photon, or proton beam (proton therapy) via a particle accelerator into the volume of the tumor.
• Brachytherapy involves putting radioactive sources in contact with or inside tumors, for more targeted treatment. It can be prescribed for certain prostate, gynecological, anal canal, and eye cancers.

The main biological effect of ionizing radiation is to break the DNA strands of the tumor cells – either directly or through the formation of free radicals – which leads to the death of these cells.

Every radiation treatment requires a period of preparation, during which the specialist makes a precise calculation of the volumes to be irradiated based on scans performed in the treatment position, sometimes merged with MRI or PET-scan images. These images also make it possible to locate the healthy organs adjacent to the treated volume and to draw up a personalized treatment plan for each patient.

The precision of the treatment’s delivery and the quality controls implemented are crucial to ensuring the most effective results possible.

The estimated dosimetry is prepared by dosimetrists, checked by medical physicists, and validated by radiotherapy oncologists. The treatment plan’s parameters are verified by the radiophysicist.

The positioning of the patient on the treatment table is carefully checked every day. The dose actually received is systematically measured and compared to the planned dose. Throughout treatment, a weekly medical consultation provides for strict medical follow-up.