Can breast cancer radiation treatment cause stomach issues?

Usually not: Gi symptoms during breast cancer radiotherapy are uncommon but not unheard of, especially for right-sided cancers where some of the liver may be in the lower part of the field. Ask your radiation doctor to see how much liver is being irradiated and if it can be minimized. More often this problem is related to chemo or hormonal treatment or a diet supplement.

Not likely.: Although anybody can have any reaction to anything, this is not likely. It would be more likely for a chemotherapeutic agent to do something like this.