I too had SCC at base of my tongue. I had 35 radiation treatments and 3 chemo treatments completed 3 weeks ago. That thick sticky mucus is normal and difficult. I found it was nearly impossible to sleep without constantly waking up to spit the stuff out. Many times I tried sleeping in a recliner at near vertical position which seemed to help. Drinking ice water or sucking on ice chips seemed to help with the mucus. It is finally starting to go away but that tooke 3 weeks after treatment. Good luck.