@keithl56 Hey, I was the commenter on your other thread who suggested you contact Veracyte directly. I'm glad that worked out for you -- they were very helpful when I had to deal with them, too.

I agree fully with your interpretation here. If your Decipher risk score comes back high, then that would be cause to skip AS. But a low risk score would not be conclusive because of the use of Gleason 6 tissue.

If you get pushback from your doctor on this, I recommend standing your ground because your concerns are legit. Relevant anecdote: I had Decipher testing done both on my needle biopsy tissue and on my prostate tissue removed during RALP. While the overall risk scores were close, the underlying genomic details -- which I saw by requesting the GRID reports for each test -- were wildly different. It was as if two entirely different patients had been tested: the gene expression scores were meaningfully farther apart for more genes than they were close together. The fact that the risk scores turned out similar was a fluke: both tests happened to characterize the cancer as highly aggressive, it's just that the two samples appeared aggressive in very different ways.

I wound up discussing this with multiple oncologists at top COEs, and the answer I got was that Decipher testing is very vulnerable to what's known as tumor heterogeneity (feel free to go down the rabbit hole of researching that). Decipher does not directly sequence the DNA of the tumor cells in the way that certain somatic tests do; rather, it evaluates the phenotype of the cancer by looking at the strength of expression across a set of gene signatures. This, apparently, can be more prone to sample-driven fluctuation than direct gene sequencing.

I still think Decipher has value at various stages of diagnosis and treatment, but this experience has significantly tempered my prior inclination to really lean heavily on the specifics of the results.

What I would recommend in your case, if the Decipher comes back low, is that you ask your care team about supplementing with a second test using a different protocol. You might want to consider ArteraAI, since that does not require tissue samples be sent (and it seems like you have limited Gleason 4 tissue available): Artera uses digital images from the pathology slides that your biopsy lab has already prepared.

Here's an overview of the test that shows a sample report on page 9:
https://artera.ai/wp-content/uploads/ArteraAI-Prostate-Test-Guide.pdf