What is your PSA threshold for obtaining PSMA PET for biochemical failure after RP?

I typically order a PSMA PET after ~0.20. Sometimes lower if there are multiple aggressive features or poor prognostic factors (i.e. SVI with no lymph node dissection and persistently positive PSA of 0.15 after RP). This approach seems to be a reasonable threshold to me based on two considerations:

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Any good references/articles that discuss considerations in the setting of (potentially false) negative scans?

I’ve had a couple of patients with fairly high BCRs (PSA >3.0) with negative restating PSMA and they have not been on ADT nor do they have unusual/atypical histology.