What Is Radio Therapy?

Radiotherapy, also called radiation therapy, is the treatment of cancer and other diseases with ionising radiation. There are generally two types — internal radiotherapy and external radiotherapy. 

Internal radiotherapy is given in one of two ways: either by placing radioactive implants directly in a tumour or body cavity, or by giving a radioactive liquid, either through mouth or as an injection into a vein. Ionizing radiation deposits energy that injures or destroys cells in the area being treated (the `target tissue') by damaging their genetic material, making it impossible for these cells to continue to grow. Although normal cells are also affected, they can repair themselves more effectively. The damage to normal cells is usually temporary and has some unwanted side effects. Possible side effects include temporary or permanent loss of hair in the area being treated, skin irritation, temporary change in skin colour in the treated area, and tiredness. This therapy is used to treat localised solid tumours, such as cancers of the skin, tongue, larynx, brain, breast, or uterine cervix. It can also be used to treat leukemia and lymphoma.

External radiotherapy does not make you radioactive, and is perfectly safe.

X-rays were the first forms of photon radiation to be used to treat cancer. Linear accelerators and betatrons are used to produce high-energy X-rays. The higher the energy of the x-ray beam, the deeper the x-rays can go into the target tissue. Gamma rays are another form of photons used (cobalt irradiation), in radiotherapy.

Particle beam radiation therapy, which uses fast-moving subatomic particles like neutrons, pions, and heavy ions are also used to treat localised cancers. It is referred to as high linear energy transfer (high LET) radiation.

Published in The Hindu on Mar 7, 2002.