Radiation therapy is basically a treatment option for different types of cancers. It involves use of high-energy x-rays to destroy cancer cells. These rays actually break up the DNA of cancer cells disrupting their growth and division. This therapy can even potentially kill the cancer cells. There are two types of radiation therapy namely external beam radiation therapy and internal beam radiation therapy. The former includes providing the beam of radiation onto the affected area by an external machine. However, the latter involves placing a radioactive substance in the cancerous tissue. Before radiation therapy, a patient needs to undergo a CT scan. This is basically to find the exact location of tumour. This therapy may be used alone or with other treatment options like surgery or chemotherapy. Radiation therapy may cause certain side-effects. Read on to know about them.