Sorry to hear your wife has a swollen tongue. I am a tongue cancer survivor but was fortunate enough to have not needed radiation. However, I'm sure radiation may cause a side effect like this. Have you asked the doctor about this side effect? One thing I know is you should always ask any question you may have; even if you think it's not important, it could be. So never hesitate to ask. Good luck to you and your wife, hope she is cancer free now!