It can also be thrush, basically an oral yeast infection, oral candida, which is common during radiation, and or chemo treatment that may have symptoms of a swollen tongue. Usually the tongue also has a white coating that can be scraped off. It is easily treated, if treated properly, usually by antifungals. Dehydration may do it too. Bring it to the doctor(s), nurses attention during the week. I had my mouth sprayed everyday at my treatment center to help prevent thrush, mucocitis, and last year needed a few IV hydrations during the week by the RO nurse, in addition to the others at chemo, and was actually hospitalized for that, but mainly for a blood transfusion, but things can get out of control quickly.

Good luck.