In Radiation therapy, high-energy rays or radiation are used to destroy cancerous cells. Radiation either comes from machines or from radioactive substances that are inserted into the organs affected by cancer.

Radiation not only kills cells it also prevents them from growing or spreading. Because cancer cells spread very fast than most of the normal cells, radiation therapy can successfully treat many kinds of cancer. Radiation affects normal cells too but most of them return to normalcy after the treatment is over.

Radiation treatment is usually combined with surgery for treatment of cancer. Doctors can use radiation before surgery to shrink the tumor that makes it easier for the doctor to perform surgery.
Radiation therapy can also be used after surgery to ensure that no cancerous cell is left. But the disadvantage of this therapy is that along with cancerous cells, it can also destroy normal cells.

- Types of Radiation Therapy:
There are two types of Radiation therapy:

• External: In this therapy, high-energy rays are aimed at cancerous cells and tissues surrounding itthrough machines.Different machines can be used for treating different types of cancers. But the most common machine used for radiation therapy is linear accelerator.
• Internal: Also known as implant therapy, In this therapy radioactive substances are inserted in the body through tubes to kill cancerous cells. The source of the radiation (such as radioactive substances) is called an implant.

Sometimes unsealed radioactive materials are injected into the body. Treatment of cancer with radiation therapy is very costly.