What types of radiation are used for cancer treatment? 5
1. X-rays and gamma rays are packets of energy or photons. They are the forms of radiation most commonly used to treat cancer; in fact, x-rays have been used for over 100 years. 2 The two types of radiation differ only in their source. X-rays are generated by having electrons strike a target, while gamma rays are produced by nuclear disintegration of radioactive atoms (isotopes). X-rays and gamma rays are very penetrating radiation, and are particularly useful to attack tumors located in deep tissues and organs. 2. Particulate radiation uses subatomic particles that have mass. Electron beams have a very low tissue penetration, so oncologists use them to treat skin conditions. Neutron beams may be more effective than x-rays to treat salivary gland tumors. Proton beams can be focused to deposit their energy over a very small area, so have found application for cancers that are difficult or dangerous to treat with surgery, such as certain brain tumors.
How does radiation exert its effect? 3
The absorption of radiation energy in tissues can lead to ionization. This can kill cells by producing breaks in its nuclear DNA. A second mechanism is through the formation of free radicals from water in the cells. These free radicals are highly reactive, and cause cell damage. A primary concern in radiation therapy is to kill cancer cells while minimizing damage to healthy cells. Rapidly dividing cells such as cancer cells are more vulnerable to the effects of radiation. This may be due the ability of normal cells to more readily repair DNA damage.
Working against the effectiveness of radiation therapy is the finding that there is a direct correlation between radiosensitivity and oxygen levels in the tumor. Tumors are notable in having a poor vascular system, which leads to low tumor oxygen levels. Although attempts to oxygenate tumors to make them more sensitive to radiation have been largely unsuccessful, the use of anti-angiogenesis inhibitors may be a better approach. Angiogenesis is blood vessel formation, and agents that inhibit this process make the endothelial cells lining the blood vessels more sensitive to radiotherapy.
What types of radiation therapy are used? 4
1. External radiation therapy is the most common type of radiotherapy, and is typically administered on an outpatient basis. Intraoperative radiation therapy is a form of external radiation that is given during surgery. Although surgeons do their best to remove a tumor, radiation can be applied to assure removal of any remaining cancer cells from the site. Many advances have taken place in the field that has improved the effectiveness of treatment while minimizing harmful side effects.
| Here's the follow-up discussion on this article: | View all related messages |
For a complete listing of article comments, questions, and other discussions related to David Olle's Cancer Treatment topic, please visit the Discussions page.