Please forgive me I'm repeating myself once too often here, but for readers who may not have seen the older threads:

1) The promise of ctDNA tests for presence/recurrence seems to be less than advertised for pancreatic cancer (PDAC in particular). My PA told me if Signatera is positive I almost definitely have cancer. If Signatera is negative, I might still have cancer. Two negative Signateras and one negative Grail/Galleri shortly before my recurrence was identified on MRI (and hinted at by my rising CA19-9) demonstrate there is something sneaky about PDAC cells that evades these tests. Likewise, the post-recurrence spread obvious on imaging while Signatera continues to report "0.00" ... (Fine print on the report indicates cancer may be present below detectable threshold. One cell is all it takes... 🙁 )

2) CA19-9 is not the holy grail, but one indicator that can be combined with others to add confidence to a conclusion. It's cheap and easy and should be done frequently pre-op and post-op so you know your own normal and have a "low noise" data set to help detect trends.

3) https://pubmed.ncbi.nlm.nih.gov/34751822/
It's only one paper, but recent, and says:

"During the last twenty years, it has been well established
that all surgical approaches to pancreatic cancer need to be
supplemented by adjuvant therapy."

and

"it remains clear that resectable pan-
creatic cancer patients should not be treated with a neoadju-
vant therapy outside clinical studies"

The paper does also have some blanket statements I disagree with, and I acknowledge that I don't have the medical training to judge the paper's accuracy. The authors do cite references for most of these statements, but I think some come across as more broadly applicable than they're meant to. I also acknowledge that I can't remove confirmation bias from my interpretation of scientific papers, given my own experience and outcome.

< rant deleted about the mythical median patient>

Summary: Err on the side of caution. Your life depends on it!!!