When is radiation therapy used to treat cancer and when is chemotherapy used?

[Caitlin]

I'm trying to figure out when radiation therapy is used to treat cancer opposed to chemotherapy. Are there certain types of cancer that one of the other is used on? Or is it a matter of have cancer widespread throughout the body, opposed to having cancer in a small area?

[tinmuning]

Radiation therapy can be used both as sole regimen or as an adjuvant to other regimen such as chemotherapy & surgery. When used alone, radiation therapy can be curative (where the goal is to eliminate all signs of cancer) & palliative (which relieves symptoms, including pain). When combined with other treatments, it can shrink a tumor before surgery, make tumors more receptive to chemotherapy drugs and make sure that all cancer cells are killed after surgery. It can also be given in areas that do not have evidence of cancer. This is done to prevent cancer cells from growing in the area receiving the radiation. This technique is called prophylactic radiation therapy.

Radiation therapy may be used to treat almost every type of solid tumor, though the dose & whether it is given alone depends on a number of factors, including the type of cancer and whether there are tissues and organs nearby that may be damaged by radiation.