Download Ionizing Radiation

Gemma Downey
Radiation Therapy
Also called radiation oncology, radiation therapy is the
use of ionizng radiation as part of cancer treatment
to control malignant cells
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.
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
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.
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
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
Dosages
Dosages are split up, or fractionized, over time so
normal cells can recover and tumor cells become less
efficient.
Radioresistance
Different cancers respond differently to radiation
therapy. Highly radiosensitive cancer cells are killed by
smaller doses of radiation
1. Leukemia – highly radiosensitive
2. Epithelial Cancers – moderatley radiosensitive and
require a higher dose
3. 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
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
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 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.