stage 4 stomach cancer

Hi,
My dad is 53 and has just been diagnosed with stage 4 stomach cancer he also has cancer and it has spread to his liver and the soft bone of his hip. currently he is too weak to be able to withstand the chemo as the tumor is partially blocking his esophogus so he hasnt been able to eat. The Dr. said that they would hit that tumor hard with radiation in an attempt to shrink it so that he could eat again and get stonger for chemo. Does anyone have any diet suggestions? whats the prognosis like? any info would be greatly appriciated

thanks