The objective is to:
"...hold a good weight, keep your energy up, maintain your muscle mass, good nutrition and hydration"... Otherwise you need a feeding tube".

"At MDA a feeding tube can be placed at anytime during treatment... and should not be your only source of eating and drinking".

(Source: Denise Anderson, Sr Clinical Dietitian , Clinical Nutrition. University of Texas, M.D. Anderson Cancer Center)

I know at the 'bitter end', even with a PEG, the nausea made it hard for me to keep enough down.