Psma scan limitations

[rnewman751]

What is the lowest psa level a psma scan can pick up Mets? I've been at 0.05 for 4 consecutive months. I had prostatectomy February 2014. Salvage imrt September 2015. 2nd time detectable psa recurrence June 2019 @ 0.02 Creeping up to current 0.05 as stated above. Thank you.

[Justfor_]

Mother nature doesn't function like some silly doctors think she does. For any PSA value there a probability that diminishes in concert with PSA and most importantly with its rate of rise. There are examples, taken off published studies, that indicate positive detections at the 0.0x range. Off the top of my head I would say that your probability is somewhere between 20 and 30 percent as your rate of rise is not short . Silly doctors will parot the 0.2 value and sillier ones will prefer 0.5.

[rnewman751 in reply to Justfor_]

Last year June 2019, Dr. Morris @ MSK told me to contact him when my psa reaches 0.05. I'm reluctant to start any treatment because of the low level and rather slow doubling time. Thanks for your time and response.

[Justfor_ in reply to rnewman751]

Most people don't understand that there is not a perfect correlation i.e. 1:1 between PSA and PSMA. So, there is an ambiguity factor at the two extremities of the range. Cells that express PSMA with little or no PSA and just the opposite. The latter explains the fact that the PSMA test even at high PSA counts is not 100% efficient. If memory serves it is 95% at integral PSA values like 1, 2 or so.

[j-o-h-n in reply to rnewman751]

If Dr. Morris told me to stand on my head..... I would.....

Good Luck, Good Health and Good Humor.

j-o-h-n Thursday 12/31/2020 4:37 PM EST

[rnewman751 in reply to j-o-h-n]

Thank you j-o-h-n. Happy New Year

[GP24]

You should get salvage radiation at a PSA level between 0.2 and 0.5 ng/ml. However, you already had salvage radiation. In that case the level of 0.2 to 0.5 is of no concern any more. My recommendation is to wait until the PSA level reaches 2.0 ng/ml and then discuss further treatment options with your doctor.

Therefore I would not get a PSMA PET/CT now, you can wait until 2.0 and this level will provide good results - from a diagnostic viewpoint.

To see a met on a PSMA PET/CT at a PSA level of 0.05 is almost impossible, therefore the scan will be waste of money.

[rnewman751 in reply to GP24]

Thank you for your response.

[Tall_Allen]

A PSMA PET scan detects prostate cancer is fewer than a third of men who have PSA<0.2.

Your PSA is terrific. The only problem is you are using the wrong PSA test - you would not possibly do any kind of treatment until PSA reaches at least 0.1. You are only causing yourself needless anxiety.

[rnewman751 in reply to Tall_Allen]

That is certainly the truth. What do you mean I'm using the wrong PSA test? Thank you T.A.

[Tall_Allen in reply to rnewman751]

You are using an ultrasensitive PSA test for a purpose for which it was never meant. Its only use in deciding on SRT, which you have already had.