I'm going to be offline for a few days (I think), and just wanted to elaborate a little more on my thought process behind the previous posts, with the repeated disclosure that I have no medical training.

If @mmatunis was a patient with no history of cancer but did have the increasing CA19-9 results described, I would not be advocating for chemo this early, but I would encourage a deeper, quicker investigation into all the possible causes with an eye toward "worst first." That is, benign is fine, and benign causes can be investigated more leisurely. But if the worst possible cause is indeed cancer, increase the frequency of imaging, CA19-9 testing, and ctDNA regardless, because delay could prove catastrophic. And with that said, most of the benign causes listed earlier can be detected with basic blood tests and/or imaging.

However, with @mmatunis' history of recent cancer, and recently much lower CA19-9 levels, I would assume the worst and work backward from there. It's entirely possible there is inflammation underlying the rise, but it's also possible to have inflammation (or other benign causes) AND cancer. You wouldn't want to treat just inflammation and overlook the cancer. An anti-inflammatory might actually reduce any CA19-9 elevation caused by inflammation, but a decrease in that number might also mask an increase truly due to recurrent cancer and delay treatment. [My very first signs of cancer were elevated liver enzymes associated w/ bile duct blockage. Liver ultrasound was inconclusive, and dietary change plus elimination of Tylenol brought the enzyme levels down temporarily, delaying my initial diagnosis by a couple weeks.] On the other hand, while treating @mmatunis with Folfirinox might drive CA19-9 down (especially with a prior good response to it), I think it would likely be due to killing cancer cells. If it did mask inflammation or another cause, that would theoretically be a more benign issue that could be treated with less urgency.

Finally, from the basic logic perspective, if you miss the window of opportunity to kill cancer or confine it to another surgically resectable/radiatable area, you're probably going to be on chemo the rest of your life with the same side effects (neuropathy, risk of organ damage, etc) AND have metastatic cancer on top of that. It's not a great analogy, but starting chemo now on the assumption of disease could be viewed as "adjuvant therapy started a good bit later than usual." 😉 I would personally rather go through that for a while and deal with organ damage than go through it for a lifetime and deal with cancer.

I hate to sound like Chicken Little ('The sky is falling!"), but @mmatunis' case sounds too much like my own which went from negative biopsy and negative ctDNA to metastatic stage-4 while we waited 6 weeks for confirmation. Immediate surgery (Whipple revision or total pancreatectomy) might have avoided that outcome. It could have been difficult to justify at the time because of the negative biopsy, even though the primary tumor was visible at the original surgery site on MRI. However, I already had a chemo port that could have been put to use immediately, and that might have made a difference in stopping the spread. Adjuvant therapy for Whipple normally begins about 2 months after surgery. Starting me on chemo when my recurrence first showed up on MRI would have been at the 4.5-month mark after surgery, and while not conventional, would not have seemed unreasonable to me.

Doctors sometimes take offense at what appears to be "questioning the science," but they also sometimes need to be gently reminded that they're treating an individual patient, not a median statistic.