Hello,
Not eating is not good but what is worse is not drinking liquid and keeping swallowing working. Dehydration comes on very fast and can send him to the ER in a blink. Keeping the throat and swallowing working is critical too; otherwise there is chance he might be on tube long term.

I know you do the best you can but keep trying.

As to gagging, get some anti nausea meds.

Don
Male, 57 - Great health except C
Dec '12
DX: BOT SCC T2N2bMx, Stage 4a, HPV+, multiple nodes
1 tooth out
Jan '13
2nd tooth out
Tumor Board -induction TPF (3 cycles), seq CRT
4-6/2013
CRT 70gr 2x35, weekly carbo150
ended 5/29,6/4
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