Radiation in the treatment of cancer
The three types of radiation are highly energetic particles. Each type has its own distinct ionising and penetrating property. Radiation can ionise the molecules in living cells, in particular the DNA molecule. This can affect the ability of the cell to grow and divide. This affect of radiation on living cells is made use of in the treatment of cancer.
The process of using radiation in the treatment of cancer is called radiation therapy or radiotherapy. During radiotherapy both cancer cells and normal cells are damaged, however normal cells can recover from the effects of radiations.
There are three types of radiation therapy;
- External radiation therapy
- Internal radiation therapy
- Systemic radiation therapy
External radiation therapy
In this type of treatment a machine is used to aim high energy radiation to the cancerous cells from outside the body. A machine called a linear accelerator (LINAC) is commonly used for this type of treatment. In this device a highly energetic electron beam is used to generate x-rays or gamma rays through the collision with a suitable target material. The x-rays/gamma rays are then focused into a beam which targets the region requiring treatment. External radiation is used to treat most type of cancers for e.g. cancer of the breasts, brain, bladder, lungs etc. It is also used in certain cases when the cancer spreads to other parts of the body from the primary site.
Internal radiation therapy
In this type of therapy the radioactive material is sealed in needles, wires, seeds or flexible tubes and placed directly into or near the cancer cells. The radioactive isotopes used in internal radiation therapy are Iodine 125 or Iodine 131, Strontium 89, Phosphorous, Palladium, Cesium, Iridium or Cobalt. As the isotopes decay naturally, they emit radiations which target the nearby cancer cells.
Systemic radiation therapy
In this type of therapy a radioactive substance is swallowed or injected into the body and travels through the blood/circulatory system, locating and destroying the cancer cells. Systemic radiation therapy is used in the treatment of some types of thyroid cancer. The radioactive isotope, Iodine 131 is used. This is because thyroid cells naturally take up this radioactive isotope. For some types of cancer treatment the radioactive substance is joined to an antibody. The antibody travels through the blood and recognises the target cells; it binds to the proteins of these cells exposing them to the radioactive substance.