Dear dj222: If radiation has been recommended, there is usually a good reason. You might review this with the doctor. While we don't use the word cure much in the cancer world, it does not mean that this cancer will come back. In many cases, the cancer stays gone for a very long and indefinite time. However, we always have to be prepared in case it does return.
I wish I could say there was a cure for breast cancer but sadly, there is not. Best wishes to your Mother.