I am reminded that years ago in the midwest,Iowa, there was a doctor named Dr.Norman Baker who was using radiation, I believe it was X-rays but could have been some other radiation, to kill cancer cells. He was run out of town and the Country for being a quack. The medical profession had much to do with his going. As I recall the Dr. set up his practice across the Rio Grande near Loraedo Texas. I don’t recall what went on as to his curing cancer but there were people who went for his treatment(s).
Radiation is routinely used to treat cancer. Cancer cells have less resistance to radiation than normal cells. The debate is whether it makes sense to accept the risk of radiation to healthy tissue. High level radiation certainly is associated with a cancer risk to healthy tissue. One could draw a straight line from that risk to zero-zero, and that is what is routinely done. The proponents of low level radiation assert that rather than use a straight line, they should draw their straight line to zero-less than zero, so some low level of radiation is associated with positive benefits for healthy tissue, rather than merely act as a treatment for small cancers that you don’t know about yet. I don’t know what a mechanism for such a health benefit would be.