@rabbit22 , you're very welcome.

Repeating the standard disclaimer that I HAVE ZERO MEDICAL TRAINING...

...Regarding the genetic testing in general (i.e., blood test for inherited or spontaneous mutations), the GI docs seem to push that off toward oncologists and genetic counselors for their specialized ability to explain results to the patient.

If you don't have an oncologist yet, you could ask the GI doc to refer you to a genetic counselor for the basic (inherited/germline) test, because that would help identify whether you are a high-risk patient or not. Certain mutations and/or close family members with similar cancers could put you into a category that justifies closer monitoring than the average patient.

FWIW, MD Anderson just updated their pancreatic cancer screening recommendations here:
https://www.mdanderson.org/content/dam/mdanderson/documents/for-physicians/algorithms/screening/screening-pancreatic-web-algorithm.pdf
On page 2 it shows their high-risk criteria and the list of mutations considered risk factors.

There is also set of Fukuoka Guidelines / Classifications for managing IPMNs. Last update I could find was 2017, discussed here:
https://www.sciencedirect.com/science/article/abs/pii/S1424390317305161?via%3Dihub
and with a nice flow chart here:
https://www.endoscopy-campus.com/en/classifications/impn-fukuoka-classification-guidelines/
Since you are getting an EUS soon, you will be at the big decision block "Are any of these features present?" and answers to that will probably guide your next stage of diagnosis/treatment. If the answer to that question is "No," and the EUS confirms the size reported on your MRI (1.2 cm), then I interpret that as moving you to the second box on the bottom row (CT or MRI every 6 months for 1 year, then once per year for 2 years, then every other year if no change).

But, recalling that you are exhibiting 3 out of the 4 symptoms where Anderson's chart says, "Proceed to diagnostic evaluation," don't let them short-change you on the diagnosis.

Two additional thoughts:

1) The EUS procedure itself can aggravate your pancreas and cause pancreatitis, which could elevate your CA19-9 level. Have you already had that tested? It's good to know your own baselines in order to track changes. But it would be ideal if they could test it again before your procedure so it's not artificially induced to a higher level.

2) As I mentioned before, my EUS biopsy did not find malignant cells. A question I wish I had asked my GI surgeon was whether the tissue looked "normal" rather than just whether malignant cells were present or not. Although he diagnosed pancreatitis, I had never had any symptoms of pancreatitis before or after my Whipple surgery. Pancreatic cancer cells (PDAC type at least) frequently wrap themselves up inside of a "stroma" which is a fairly dense envelope of other tissue (fibroblasts and pancreatic stellate cells that produce and deposit fibronectin and collagens). Presence of this tissue would seem to me to not be "normal" tissue for the biopsied organ; even if it doesn't show malignant cells, it might indicate the biopsy only dug part way through the envelope.

In my case, I still have the main tumor that recurred at the original surgical site, plus a couple mets spread out around the abdomen and peritoneum, so there's no practical surgery or radiation option. We're just (thankfully!) keeping it all under control with old-fashioned chemo for now.