End stage colon cancer; Do you keep fighting?

My father has recurrant colon cancer that has spread to his liver and lungs.  About a week ago we were told that the cancer is not well controlled and that if he has anything to do/people to visit it should be done now.  He is currently on Erbutux and we haven't had a CT scan since July.  His last CT scan showed inprovement but in September we were told the chemo was no longer working and he was given a 6 weeks rest and then started on erbitux.  Without a current CT scan I don't know how they can tell except from blood work.  Do you think it is irresposible for a doctor to give that kind ot news without a CT scan.  Can they really tell?  I'm  currently trying to get the liver lesions treated with yttrium-90 containing SIR-Spheres microspheres.  My fathers has an HMO and this is an out of coverage treatment so I'm having to really fight to get it covered.   Should keep we on fighting for this new treatment or trust the doctor and just give up and let his last days be peaceful and not be filled with needles, tests , and doctors visits? I do see a change in him.  He is sleeping alot more and very tired.  I don't know if this is due to the treatment because it began about a week after he started on the Erbitux.  Also stangely he is talking about his parents alot.  He says he dreams of them.  Both of his parents passed away in the 80's.  It spooks me and I don't know what to say.  Is it the medication? Please reply with any thoughts comments of simiular situations.  This is such a hard time that I feel so lost and don't know what to do.