Radiation therapy refers to the medical use of high energy, penetrating waves or particles, such as X-rays and gamma rays, as part of treatment to destroy cancer cells or avoid their reproduction. Radiation therapy is often referred to as: radiotherapy; electron beam therapy; irradiation; or radiation oncology.
Radiation therapy is commonly used as one of the oldest and most effective ways to treat cancer. The principle on which radiation therapy works is that tumor cells cannot recover from radiation damage as fast as normal tissue. High-energy radiation damages the cells' deoxyribonucleic acid (DNA) — the protein that carries the code controlling most cell activities. When cells divide, their DNA should also double. Damaging the DNA, radiation therapy blocks the process of growth and any increase in the number of such cells. Tumor cells enlarge and divide faster than normal cells, therefore they are particularly vulnerable to radiation.Thus radiation therapy can kill the cancerous tissue, without destroying the surrounding normal tissues that grow slower and have enough time to recover.
It is used to treat both children and adults, as radiation use has been improved with the time. Radiation therapy may be used as the single treatment for a disease or in a combination with chemotherapy or surgery, or both.
The beginning of radiation treatment can be traced back to the end of the 19th century, when Wilhelm Roentgen (1845-1923) discovered the X-rays. The use of Roentgen rays for medical purposes quickly became a separate field of study from physics. The work of Noble Prize laureate Marie Curie (1867-1934), the Polish-French scientist who discovered radioactive elements polonium and radium, largely contributed to the advance of researches into radiation treatment. Pierre Curie (1859-1906) and Marie Curie, as well as another Noble Prize-winner, Henri Becquerel (1852-1908), were the first to suggest to doctors that they might use radioactive substances for medical purposes and they strongly committed themselves to the development of radium therapy. In the first-half of the 20th century, radium was used in various forms, followed by cobalt and caesium. The development of medical technology, especially the invention of the magnetic resonance imaging (MRI) and the positron emission tomography (PET), hugle improved and refined the application of radiation therapy.
Radiation therapy has been used: to kill cancer by itself; to decrease a tumor before surgery in order to facilitate its removal; in intraoperative radiation, to destroy cancer cells during a surgery; to kill cancer cells that have remained after surgery; in combination with chemotherapy to shrink an inoperable tumor in order to relieve a person's pain or improve the quality of their life. Some types of cancer, including an early-stage Hodgkin's disease and non-Hodgkin's lymphomas, can be cured by radiation therapy alone.
Radiation therapy is a local and painless treatment, which affects only the treated part of the body, unlike chemotherapy where chemicals go through the entire system. Generally, the benefits of radiation therapy are considered to exceed the related risks and side effects. Radiation therapy may be internal and external. The latter involves a beam radiation directed at the tumor from the outside. Internal radiation therapy, known as brachytherapy or implant therapy, involves the implantation of a radioactive source inside the body close to the tumor.
There are two types of radiation therapy — photon radiation and particle radiation. Photon radiation involves the use of high energy rays like X-rays and gamma rays. Gamma rays are obtained from the decay of radioactive substances such as radium and cobalt-60, while X-rays are produced by electron-exciting devices. Photon radiation disrupts the cells' ability grow and divide by disrupting the electrons within the cells' molecules. Particle radiation uses proton and neutron therapy. Protons are positively charged atomic particles that have mass, unlike photons.
Proton radiation has been used since the beginning of the 20th century. Protons allow directing higher radiation doses at tumors without causing more damage to the surrounding tissue. Neutrons are also particles with mass but without charge. Neutron rays are most effective in treatment of large tumors, as tumor cells are much less likely to recover from the damage caused by neutron radiation than others types of rays. Neutron radiation works in oxygen-free environment like the one inside large tumors, and therefore it is highly effective.
Radio-immunotherapy, which combines the use of radioactive substances and antibodies, is applied to treat metastasized cancers that have spread to various locations inside the body.