rising CA19-9 numbers but scans ok

My husband's numbers have been on the rise the last couple months from 325 lowest to over 1200 this week. Each time (every other week) the numbers have gone up... sometimes only 100 points, but the last couple have gone up by 300 and 400. Our oncologist and radiation oncologist both scheduled him this week for MRIs on 3 parts of the spine (bone mets) and brain, and today a full torso CT because of the rising numbers. I'm not a medical person, but looking at the reports really didn't indicate anything alarming to me... though we will meet with the two doctors Tuesday with their take on the scans. I know the scans are more important than the numbers, but the steady increase makes me think there must be something going on, and it scares me.
My husband feels ok, not great ... sits almost all the time. Fatigue, dizziness, neuropathy are his chief complaints. All of those things keep him glued to the couch. His weight is about as high as it has ever been (mid 180s, so not extreme for 5'11"), though he doesn't eat much... though of course also does not burn any energy. Walking a short distance to the detached garage he say feels like he's walked for miles. Shortness of breath, and the need to sit often.
Anyone have any thoughts? Maybe there is something in these reports that the doctors will see that I am missing. I'll be the first to admit that the medical terminology messes with my understanding. We'll learn more from the doctors on Tuesday.
Thanks for any input.
Oh, and as a side note. When my husband checked in for the CT today they had him sign something saying that medicare would not pay for this. We've never had that happen. I was parking the car so did not know about it until our drive home. Anyone have that happen? The last scan was in late December, so is under 3 months which is maybe the reason??