@asugent ,

Those CA19-9 numbers are encouragingly low. I think that may put her cancer at levels that are just too low for Signatera to detect. If you read the "Interpretations and Limitations" section of a Signatera report, it notes

"analytical sensitivity is 95% at the limit of detection (0.3 MTM/mL)."

With numbers in the range of 0.01 to 0.07 (far below 0.3, percentage-wise), I suspect there is a lot of noise in the results. I've had 20 Signatera tests since my Whipple, with 14 of them returning 0.00 while cancer was definitely present. I've only had one reading above 0.3, and as noted earlier, my CA19-9 was through the roof (2315) at the same time.

My PA told me if your Signatera score is greater than 0.00, there are definitely cfDNA molecules from your cancer floating around in your blood (i.e., some cancer present); but if the score is 0.00, it doesn't mean there is no cancer.

Your mom's "trend" (of low CA19-9 and Signatera well below 0.3) suggests (to me, non-medically trained) that her treatment is providing a reasonably good level of control. It's good to have that much info as a baseline, because any Signatera numbers above 0.3 (and increasing from there) would almost definitely be signs her treatment has become less effective.

One other possibility I would ask about is whether any of the new spots her doctors have found are definitively descendants of the original pancreatic cancer. There is always the possibility a few PC cells are floating around but other spots are from a new primary cancer elsewhere (or cells with mutated DNA that no longer matches the original tissue her Signatera test was built from).

Repeat disclaimer: I have zero medical training!