I'm still looking, but I haven't found any literature yet about cases of regular advanced prostate cancer progressing without expressing PSA on the ultrasensitive test (< 0.01).

I've seen a couple about progression when PSA was < 0.5 (the lowest early tests could detect), and a fair number when PSA was detectable in the low range (< 5.0).

That's one reason they often use uPSA to give early warning of recurrence for metastatic prostate cancer.

Note that there's a different, rarer type of prostate cancer, neuroendocrine, that does not express PSA as it spreads, but the adenocarcinoma that most of us have does.