Radiation therapy is the use of high energy rays or particles to destroy abnormal cells and treat tumors, both benign and cancerous tumors. Radiation given outside the body may also be referred to as external beam treatment, X-ray therapy, irradiation or electron beam. External beam radiation is delivered using a linear accelerator ( a large machine which creates high energy rays which is positioned close to your body.) 
Radiation has been established as one of the most effective ways to treat cancer and its application has had profound positive effect on cancer survival.

How Does Radiation Therapy Work?

Normal cells in the body divide and replace themselves in an orderly process, keeping the body healthy and repairing structures as needed. Cancer occurs when cells lose the ability to control their own growth. These abnormal cells multiply quickly, forming clumps of tissues called tumors and spread to nearby tissues and organs (and sometimes to other parts of the body). 

Radiation works by affecting the building blocks of all cells in the body, the DNA. The DNA acts as the blue print for all of the cells function. When radiation is applied, the DNA of both normal and cancer cells may be affected. Since cancer cells divide more rapidly, they have a decreased ability to repair the damage caused by radiation. Not realizing that their DNA or blue print has been damaged, cancer cells die in their next attempted division. This rapid division makes cancer cells much more sensitive to radiation. 

Because normal cells don’t divide as rapidly, they have a greater ability to repair the damage by radiation and thus go on to continue to live and perform their necessary function in the body. More than half of all people with cancer are treated with radiation, and the number of patients who have been cured is rising every day.

What Are The Goals Of Radiation Therapy?

The two main goals of radiation therapy are to cure cancer and relieve symptoms such as pressure, bleeding or pain. For many patients, radiation is the only treatment needed. However, radiation treatment may also be given in combination with chemotherapy and/or surgery. Radiation can be used before surgery to shrink a tumor, and during or after surgery to kill any cancer cells that may still be present. Doctors sometimes use radiation along with anti-cancer drugs to destroy the cancer, instead of performing surgery.

How Is Radiation Therapy Used To Treat Cancer?

Radiation therapy can be given in either two forms: external or internal.

External radiation therapy is applied by a linear accelerator machine which produces high-energy rays or particles directed at the cancer site. A treatment plan is designed by the physician which typically entails a duration of 2-7 weeks, five days a week. Anti-cancer drugs called chemotherapy drugs may also be used during this treatment. The total dose of radiation and the number of treatments will depend on the size and location of the cancer, type of tumor, general health of the patient and any other treatments the patient is receiving.

Internal radiation therapy (also called brachytherapy) places the source of the high energy rays inside the body, as close as possible to the cancer cells. This delivers intense radiation to a small area of the body and limits the dose to normal tissue. Radioactive substances, typically iridium, radium, cesium, iodine, palladium and phosphorus, are implanted into the body cavity for a short time or left in place permanently.