Radiation oncology is a clinical and scientific discipline devoted to management of patients with cancer and other disease by ionizing radiation, alone or combined with other modalities.

Radiation therapy (also called as radiotherapy) uses targeted energy, including X rays, or gamma rays or electrons and radioactive substances, to destroy cancer cells, shrink tumors and thus reduce certain cancer-related symptoms.

The aim of radiotherapy is to deliver a tumoricidal dose of radiation to a well defined target volume while sparing the surrounding normal tissue thereby achieving an optimum therapeutic ratio with the minimum level of morbidity.

Radiation therapy is an effective treatment for various types of cancers in almost any part of the body.  Its two main goals are :

• To cure cancer
• To relieve symptoms

For many patients, radiation is the only treatment needed.  However, radiation treatment may also be given in combination with chemotherapy and / or surgery to shrink a tumour and during or after surgery to kill any cancer cells that may still be present.

Doctors sometimes use radiation along with anticancer drugs to destroy the cancer instead of performing surgery.  Radiation can be used as a palliative therapy, meaning that its primary intent is not to cure the cancer, but to relieve pressure, bleeding or pain by shrinking the tumours.  Palliation may not add years to the patient’s life but adds quality to the time available to him/her.

Radiation with x-rays or electrons producers free radicals within the nucleus of the cell, which damage the deoxyribonucleic acid (DNA) of the cell.  The DNA which has been exposed to radiation damage, is not