Tim,
By way of an answer to your other question, from mayo.com:
"You may be worried that radiation will destroy your healthy cells as well as the cancerous cells. But radiation is much more harmful to cancer cells than it is to normal ones. This is because cancer cells divide more rapidly than do healthy cells. Cells are more vulnerable to damage when they're dividing, making cancer cells more susceptible to radiation than normal cells are. In addition, normal cells can recover from the effects of radiation more easily than cancer cells can."


Perhaps not a complete answer, but better than "going on faith"

Good Health,

Chuck