Can radiation cure cancer or just treat it?

The treatment can lead to an individual cure. Radiation works best if there is only one location. Radiation becomes less effective when cancer is spred all over the body. Radiation also frequently will damage good tissue along with the diseased area. Because of this children are often now being offered Proton Therapy which is highly targeted and able to pinpoint only the tumor(s). Regular radiation beams penetrate the tumor and go out the other side . . while proton therapy only hits the tumor and stops. There are certain cancer types in which proton therapy will work better than traditional radiation.

the national association of proton therapy
http://www.proton-therapy.org/

Proton Therapy
http://www.radiologyinfo.org/en/info.cfm?pg=protonthera

Radiation kills cancer cells. Radiation sometimes kills all the cells and cancer never returns – this might be called a cure. Sometimes it can’t kill all the cancer cells without killing a much larger number of healthy cells, so it cannot always be given in an amount that kills all the cancer cells – this would not be considered a cure.

If there were a ‘cure’ for cancer, I wouldn’t be taking my wife for weekly treatments. Radiation and chemotherapy treat the cancer by killing it off through a series of treatments over long periods of time. Even though the patient may go into remission (said to be ‘cured’), the cancer may grow. This is why the patient is monitored for months/years afterwards.