External-beam radiotherapy is usually given in fractions, either daily or several times a week, until the total dose needed to kill the tumor has been reached. A cat with three implanted radioactive ribbons held in place by metal buttons. . Thus, the radiation dose is concentrated in a small area, and the patient is radioactive until the implants are removed or until they lose their radioactivity by decay. Intraoperative radiation therapy is a technique which is sometimes used to deliver a large dose of external-beam treatment to a tumor and its surrounding tissue during a surgical procedure. For some cancers, this is a particularly useful modality for delivering radiation therapy, since it spares surrounding radiosensitive tissues.
Radioactive iodine is injected to treat feline hyperthyroidism.
The cat is kept in isolation until most of the radioactivity has been eliminated from the body, and the pet is not of any danger to other pets or family members after it is sent home. Although many tumors in small animals can be cured or controlled by radiation therapy, some tumors cannot be effectively treated using this modality. Finally, it is of little benefit if radiation therapy cures a tumor in the mouth, for example, but the animal is found to have metastasis to the lungs a few weeks later.