@johndavis60 I have found some mentions in the literature of the rare neuroendocrine type of prostate cancer (NEPC) advancing with PSA < 1.0, and there may be a handful of cases (out of hundreds of thousands) of NEPC advancing with PSA < 0.1, but I have yet to find a mention of progression when PSA is undetectable on the ultrasensitive test (< 0.02 or 0.01). That test wasn't common until recently.

When there's something slightly concerning on a scan, my radiation oncologist does follow up, but as he told me, even NEPC expresses *some* PSA (just a very small amount that older PSA tests couldn't detect, hence the "varieties of PCa that spread without expressing PSA" thing you still read online).

It's normal to be nervous — I am too, before any scan — but you've been a good responder to doublet therapy and your PSA is still undetectable on an ultrasensitive test, so I think it's a pretty-safe bet (as safe as anything is in this world) that if any lucencies do show up in your scan, they will be non-cancer "noise" rather than cancer "signal," as happened to me with an MRI last fall. That's especially common places like the ribs, where scans can't easily distinguish between a cancerous lesion and a bruised rib healing, for example. Radiologists and oncologists have to use their subject-matter expertise, your medical history, and other test results to make a judgement call.

Best of luck!

Caveat: Non-expert layperson writing here. Discuss what I wrote with your onco.

@johndavis60 Thank you for the rest of the story. I can understand your nervousness. Guessing you will be asking about the type of prostate cancer you have? Do you have a high level of Cribriform? I was Gleason 9 Grade 5 with 10% Crib. in one pin. Second opinion research doc yawned and I laughed.