Does a change in CA19-9 indicate change in tumor?

My husband is back on the full Fulfirinox and numbers have gone up significantly. Now over 900 (lowest was less than 400 in July). Hoping the surge from two full treatments caused this jump. https://www.sciencedirect.com/science/article/pii/S2468294221000952
He'll have a CT scan in about 3 weeks (after his 4th treatment). Someone mentioned MRIs being better than CTs? But I couldn't find why.

If his disease is also in his liver, an MRI will be ordered.

I'm curious as to how you arrived at that logic, ma'am? My pancreatic acinar cell cancer metastasized to my liver as shown by a CT scan last Aug. There was one PET scan. I've had nothing but CT scans to check progress of the chemotherapy since? Why would an MRI be ordered?

My surgeon tells me an MRi gives him more visibility into the liver for potential surgery.

Lots of material out there on this topic.

Here’s a summary that is straightforward and discusses effectively.
https://pubmed.ncbi.nlm.nih.gov/31943576/

Good info and thanks. Gives me some ammo to discuss with my oncologist. I've been concerned about radiation exposure from CT scans as I've had 14 of them since I was diagnosed with PACC last Aug. The excessive number is partly due to scans required when I was in a clinical trial at the NIH from which I've been released. I was always wondering why none of the scans were MRI, which from what I understand, do not expose a person to any radiation.

I too have PACC and switched over to MRI with/without contrast due to concerns of cumulative X-radiation. Of prticular concern is the potential of a new primary tumor developing in ling tissue. This was of concern in patients that received CT scans between the period of 1979-1984 when more radiation exposure was required for imaging to compensate for less sensitivity of systems in that time period. As a 12 year survivor of stage IV PACC, I was receiving frequent CT scans for the first five years of at least 4/yr. At the recommendation of several oncologists, I switched to MRI about 7 years ago.

Some people raise issue with the contrast medium gadolinium. A newer generation of gadolinium is in use. I have been keeping vigil for studies on long-term use of gadolinium and long-term effects. The FDA has a group to collect clinical reports on adverse reactions resulting from short and ling-term use of gadolinium. At present, there have been no advisories except for those that already have impaired kidney function and their are advisories in its use in this cohort with a pre-existing condition.

Very, very useful information and thanks for taking the time. I was declared stage 4 in Sept of last year and was told I had likely less than a year to live. 7.3 cm. tumor on my pancreas, several lesions on my omentum and 3 lesions on my liver which were all proven to be PACC with biopsies from a laparoscopic procedure. After 12 cycles of Folfirinox ending in early Apr. of this year, the only thing visible on the CT scans since Apr. is one remaining tumor on my liver. Which is growing and now 6.3 cm. My oncologist is having the same surgeon that did the laparoscopy last year to do another one this coming Wed. The oncologist's plan is if there's evidence of problems on the peritoneum/omentum, I'd likely go back on the Folfirinox. If there's no evidence, then he plans to have the liver tumor burnt off with radiation, microwaves or radioactive beads. And I guess I'd be on some maintenance cancer preventive drug the rest of my life. Probably more than anyone here wanted to know, but thought some of it might be of use. This is one nasty, hateful disease.

Getting to maintenance can be a good thing. I have been there for over a year. I started off with a pnet that spread to my liver and a few other places. I didn't have options other than chemo CAPTEM. It saved my life. I now am on just capecitabine for maintenance.

Had the laparoscopy yesterday and looks like good news. No evidence of any cancer except the one tumor on the liver, about 6 cm. The CT scan done in Sept. of last year showed a 7.3 cm tumor on the pancreas, several lesions on the omentum and 3 lesions on the liver. All not there when he did the laparoscopy yesterday except the liver tumor and he took several tissue samples from it for analysis. My oncologist and the surgeon are calling this thing an "escape tumor". One that somehow becomes resistant to chemo. So, from what I understand, the plan is to use radiation to burn off the liver tumor, put me on some kind of anticancer maint. drug and do scans periodically. And I'm going to see if the VA will pay for MRI's instead of CT's. Little concerned about radiation exposure from 14 CT scans I've had since this journey started. And I'm attributing my results yesterday to some divine intervention also.