Post on 24-Dec-2015
Gemma Downey
Radiation TherapyAlso called radiation oncology, radiation
therapy is the use of ionizng radiation as part of cancer treatment to control malignant cells
Adjuvant and Palliative TreatmentRadiation 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.
How It WorksRadiation is energy that travels in waves
(electromagnetic radiation) or high-speed particles.
Ionizing radiation is given off by:Radioactive material (radon)High-voltage equipmentNuclear reactionsStars
Ionizing radiationIonizing 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.
HypoxiaOne 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
DosagesRadiation Oncologists decide the dosage.
Dosages are measured in the unit gray. Oncologists adjust the amount given by
considering:Type of the cancerLocation of the cancerWhether the radiation therapy is given before
or after surgery
DosagesDosages are split up, or fractionized, over
time so normal cells can recover and tumor cells become less efficient.
RadioresistanceDifferent cancers respond differently to
radiation therapy. Highly radiosensitive cancer cells are killed by smaller doses of radiation
1.Leukemia – highly radiosensitive2.Epithelial Cancers – moderatley
radiosensitive and require a higher dose3.Renal Cell Cancer – quite radioresistant so
higher doses are needed; so high that rhwy may not be safe in a clinical practice
Effectiveness on Different CancersLeukemia 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
Types of Radiation Therapy
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)
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
Unsealed Source RadiotherapyRadioactive 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.