My sister has had 1 kidney protocol ct scan and 1 abdomen pelvic ct scan they were 4 years apart she is worried about radiation. what are her chances of cancer from these scans?

Zero percent chance: As long as there is a good medical reason for a CT scan, it is fine to do. If repeated scans are planned, to follow some sort of serious illness, a patient can ask his doctor what other options there are, in order to decrease the total number of scans in her lifetime. There is a 0% chance of a typical person getting cancer from two typical CT scans, mathematically rounded of course. No worries.