FWIW, I had blood testing done (germline via Invitae) which first identified my ATM mutation. I had the Guardant 360 blood test before and after Whipple, which also detected the ATM mutation, but couldn't tell (based on the frequency) whether it was germline or somatic. But since Invitae already identified it as germline, that uncertainty didn't matter.

Last month, they finally sent my 20-month old Whipple tissue (and recent blood) for testing at Tempus. Their blood test also identified only ATM, but their tissue test identified a KRAS G12D mutation (at about 4%), so maybe the tissue testing is substantially more sensitive than blood (especially for solid tumors like PC). Definitely a question worth asking.

Now that I'm 21 months post-Whipple and possibly developing drug resistance, I wonder if there are even newer mutations in my tumor that have developed over time, with all that exposure to Folfirinox and GAC. (Isn't that the concept behind evolution?)

I might be getting a new tissue sample taken and tested if I get into the trial I applied for. But it seems like a needle-in-the-haystack problem searching for any of a billion possible mutations, when the best available tests only check for a few hundred of the most common ones.