Radiation Therapy

1. Radiation Therapy Gemma Downey

2. Radiation Therapy Also called radiation oncology, radiation therapy is the use of ionizng radiation as part of cancer treatment to control malignant cells

3. Adjuvant and Palliative Treatment Radiation Therapy may be used for adjuvant cancer treatment (supplemental treatment following surgery). It is given where the disease has been removed, but the patient could relapse It is used as palliative treatment when you can’t cure the disease, but can offer some relief and control of the disease.

4. How It Works Radiation is energy that travels in waves (electromagnetic radiation) or high-speed particles. Ionizing radiation is given off by: • Radioactive material (radon) • High-voltage equipment • Nuclear reactions • Stars

6. Ionizing radiation Ionizing Radiation can break chemical bonds because of its high energy—it can even destroy the nucleus of a cell. When it passes through body tissues, it can damage DNA. Cancer cells cannot repair sub-lethal damage compared to most healthy cells. This causes cancer cell division to reproduce more slowly—or die. A beam is fired at a tumor to do this.

8. Hypoxia One thing can inhibit radiotherapy—it is a low-oxygen state of a solid tumor called hypoxia. If a solid tumor outgrows its blood supply, its 2 or 3 times more resistant to radiation therapy. Scientists are researching blood substitutes that carry oxygen

9. Dosages Radiation Oncologists decide the dosage. Dosages are measured in the unit gray. Oncologists adjust the amount given by considering: • Type of the cancer • Location of the cancer • Whether the radiation therapy is given before or after surgery

10. Dosages Dosages are split up, or fractionized, over time so normal cells can recover and tumor cells become less efficient.

11. Radioresistance Different cancers respond differently to radiation therapy. Highly radiosensitive cancer cells are killed by smaller doses of radiation • Leukemia – highly radiosensitive • Epithelial Cancers – moderatley radiosensitive and require a higher dose • Renal Cell Cancer – quite radioresistant so higher doses are needed; so high that rhwy may not be safe in a clinical practice

12. Effectiveness on Different Cancers Leukemia has a high radiosensitivity and therefore onlt needs a low dose, however, they are generally disseminated through the body. Lymphoma may be more curable if its in one area of the body. Some moderately radiosensitive cancers are curable in early stages (non-melanoma skin cancer, breast cancer, cervical cancer, etc) Metastatic cancer (through the whole body) is incurable because you cannot treat the whole body

13. Types of Radiation Therapy

14. External Beam Radiotherapy(EBRT) The patient lies down and an external source of radiation is directed at the body. Kilovoltage x-rays treat superficial structures (skin cancer). Megavoltage x-rays treat deep set tumors (bladder, lung, brain, etc)

17. Brachytherapy(internal radiotherapy or sealed source radiotherapy) The radiation course is placed inside the area requiring treatment (used for cervical, prostate, breast cancers, etc). As opposed to EBRT, this therapy has precise placement at the sire of the tumor. The radiation only affects that area, exposure to nearby tissues is reduced, and if the patient moves, the radiation sources stay in place

19. Unsealed Source Radiotherapy Radioactive substances (like iodine-131) are injected into the body. In thyroid cancer, the thyroid gland will accept that iodine-131, destory the thyroid tissue, and with it, the thyroid cancer. This is dangerous because the patient becomes radioactive. The iodine is excreted through urine and the patient will need time before they aren’t dangerous to others. There are strict radiation regulations regarding this issue.