Signatera CT DNA Test: What numbers have you seen on your tests?

They scale the graph's vertical axis to accommodate your highest reading.

When my highest reading was 0.14, the graph had a range of 0 to approximately 0.15; after I got a higher reading (0.61), the graph had a range of 0 to 0.65

All my non-zero readings (range 0.04 to 0.61) have the triangle marker (as opposed to solid, filled-in circle) on the graph, indicating "Positive below analytical range" according to the footnote under the graph.

Later footnotes include the following text:

Interpretation and Limitations

Signatera is a quantitative test and reports in units of mean tumor molecules per ml (MTM/mL), which is comprised of three measured components (plasma volume, cell free DNA (cfDNA) concentration, and Variant Allele Frequency (VAF)).

The MTM/mL number will be qualified if any measured component falls outside the analytical measurement range for that component. The analytical sensitivity is 95% at the limit of detection (0.3 MTM/mL).

FWIW, my CA19-9 was 126 last week.

My last Signatera result (5 weeks ago) finally came down to 0.0 again (negative), but CA19-9 from the same blood draw was 265.

My highest Signatera result (5 months ago) was 0.61, and CA19-9 from the same blood draw was 2315.

We've been doing the Signatera test every 8-10 weeks for about 2.5 years, along with biweekly CA19-9. It's pretty evident Signatera does not provide much insight (or positive detection) when CA19-9 is relatively low (under 200-300). CA19-9 has provided much more granularity for me at low levels than Signatera.

Thank you. My doctors have said it is yet another data point but not isolating in itself. Apparently false positives are possible characteristic so it’s more of a trend marker. My latest is .07 designated as positive. Highest .5

Interestingly, 4 months after my pancreas surgery. And only 1.5 months beyond liver surgery, it was at 0.00.

My mom's Signatera results have bounced back and forth just as much as her CA 19-9. I was told this Signatera test was supposed to be able to detect cancer with pin-point accuracy. Unless my mom's cancer is playing hide and seek, I have not seen evidence of this accuracy.

@amy, How many Signatera tests has she had done, and what is the range of her numbers on the test? What has been the range of her CA19-9 numbers on the same time frame? What is the stage and status of her cancer, and what treatment is she on?

What types of numbers is she seeing?

She has probably done about 5 Signatera tests and too many to count on the CA 19-9. Signatera has ranged from 0.01- 0.07. As mentioned, it has been negative and positive.

CA-19-9 has bounced around since day one...anywhere from 34 to 180. Her CA 19-9 has never been above 200.

Currently, we see no correlation between Signatera and CA 19-9 trends,

Oh, sorry. Forgot the other part of the question. She was diagnosed at state 2b. Had chemo and radiation upfront followed by Whipple. Negative margins, no lymph node involvement. Just a couple weeks shy of her 3rd year in remission, they found cancer on her left adnexa, jutting into the bladder. Radiation got rid of most of it, and they went in to do a cleanup surgery after. Currently, she is being monitored for some heightened spots on the bladder. She is on a clinical trial of oral chemo for suspected return of the cancer. She is on Trametinib and Tafinlar to target her specific gene mutation. So far, last CT showed slight shrinkage of nodules at the bladder and she continues to feel good. On the clinical trial she is being monitored very carefully with blood draws every few weeks and CT every 3 months. She is 5.5 years out from diagnosis.

@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!

This is all really interesting and helpful to read. I asked my mom’s oncologist about Signatera testing and he said they haven’t adopted it for use yet due to unclear benefit (Cleveland Clinic). My mom has always had lower Ca19-9 levels anyway (219 at diagnosis, was always 3-6 for 4 years after distal surgery, just had a recurrence limited to the ovaries and it went up to 12, waiting to see what it is now that her ovaries were removed) so it sounds like ctDNA may not be accurate for her anyway since Ca19-9 has consistently been low?