I had 7 weeks of IMRT. The first 4 weeks were a breeze but at week 5 the mucos showed up and was a big problem for me. I had a difficult time getting much sleep as I was constantly gagging and coughing. However, I did not get any mouth sores and never had any pain. When the mucos got bad, I quit eating via mouth and used the PEG exclusively for the next 5 weeks.