PSA is a very strong, specific indicator. There are a few isolated cases in the literature of prostate cancer advancing with PSA < 0.1 or 0.2 on the regular-sensitivity test, but none that I've found so far with PSA < 0.01 or 0.02 on the ultrasensitive test. Even neuro-endocrine prostate cancer expresses a *little* PSA.

A warning, though: while they don't throw up as many false positives as PSMA-PET, MRIs, bone scans, and CT+contrast can light up for things that *aren't* cancer, like a bruised rib healing itself, or bone remodelling around an old spinal injury. Sometimes radiologists will decided to be better safe than sorry, and write that a lucency is "concerning for (new) cancer."

If that happens, don't panic. They did that to me last fall after an MRI. The oncologist told me it was almost impossible that it was cancer with my undetectable PSA and stable bloodwork (especially ALP), but the "c" word was still there, nagging at me, until a follow-up MRI last month concluded that it was just benign bone remodelling around my spinal surgery site.

Best of luck!