PSA test advice

[Scout4answers]

I found this buried in a thread and thought I would post it as it is very useful information, on A topic we are all dealing with on a regular basis

writen by Justfor_

3 months ago

I am older (72) than your husband and had my RP 29 months ago. Similar pathology pT3b (unilateral SVI, R0, N0). My first PSA at 6 weeks was 0.02 and my most recent 0.16.

I have monthly PSA tests interleaving two primary labs and occasionaly using a third one to act as an arbitrator in case a received result is more than 20% of that anticipated. Up to now I had 2 grossely erroneous results leading to banning the relative labs. I am a retired engineer and number crunching is my middle name. So, you may ask why until now I have not started salvage RT. Right? I am waiting to reach 0.2 and then have a PSMA PET/CT first before deciding on further steps.

I may have some useful advice for you:

a) Keep on taking 3 decimal digit tests, but have them more frequently. There are two foundamental information theory rules backing my advice:

i) At low values the quantization (also called rounding) error superseds the test's accuracy which is nominaly taken as 20%. This is the reason you were told that 0.05 is "unditectable". It is definitely detectable, but kind of meaningless as the rounding error between 0.04 and 0.05 is more than 20%. From 0.06 upwards the test's accuracy superseds the rounding error.

Three decimal digit reports move this limit a decade lower, i.e. 0.005 which is around or bellow the minimum detectable value, depending on the analyzer used.

ii) More frequent sampling acts as a noise reducer. All the digital electronic equipment you have in your life make use of this statistical (filtering) principle.

b) Now, why do one needs reliable samples?

PCa in its concept is a proliferate by devision proccess. This, in its pure form, is expressed by an ideal exponential curve. They take such a behaviour for granted in calculating PSADT (Doubling Time) and from this get an indication of the PCa aggressiveness. This is a lousy over-simplification. My PSA curve has a "S" shape. GP24 already mentioned stabilization bellow 0.4. My PSADT had a peak of ~6 months and now it has relaxed to ~9 months. It is true that one gambles with the odds waiting for a plateau to happen. Here, again, a denser time series will prove information earlier and at lower PSA levels. You have to do your own due diligence.

c) On another note, last year I contacted University of Tübingen, as they have a very recent lineac, (Elekta Unity). Their preliminary response was "come back when your PSA breaches 0.1".

[cesces]

I don't think you need that kind of accuracy.

It won't affect decision making.

[Justfor_]

This was my plan then, omicron COVID not in the equation.

Traveling around Europe at this time is not a wise thing to do, so my plan B is to keep things controlled until it will be.

Plan B is detailed here: healthunlocked.com/prostate...

[Cooolone]

I'm sorry, but your logic is flawed! The ultra sensitive PSA test, providing a third digit, is not useful in a diagnostic setting. Additional testing at such a high frequency may smooth the curve, but also is just added noise. Glad you eliminated the multiple labs as that too is problematic! And lastly, the 0.2ng level is not the threshold for which the PSMA-PET scan shines, that number would be 0.5ng above other tests and a most definitely at 0.8ng.

You provided some information but made a huge jump from 29 months ago to most recent (without a date) of your PSA tests. I'm curious what your actual PSADT is as measured at 10-12 week intervals... This is worth looking at and it would still appear to be low (doubling time). So yes, there's an recurrence of PSA (>0.05ng) but it's doubling time is favorable to possible local recurrence. The PSMA scan can be used to rule out distant mets and that will help to define what future therapy may be beneficial. But I think it's too early for that... But better minds will chime in I believe.

Best Regards

[Justfor_ in reply to Cooolone]

My PSA history up to the point in time when I started taking Bicalutamide.

I will not comment the rest of your writings.

Perceptions need not be commented.

Earth being a flat disc is just one of them.

PSA

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

Earth is neither flat or round............ it's polyhedron shaped.

The word polyhedron comes from the Classical Greek πολύεδρον, as poly- (stem of πολύς, "many") + -hedron (form of ἕδρα, "base" or "seat"). The Greeks have a word for It (το).

Good Luck, Good Health and Good Humor.

j-o-h-n Friday 01/21/2022 3:56 PM EST

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

Since we are roaming on the alleys of solid geometry what is the name of the first .....hedron Γιάννη?

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

Easy: Lopadotemachoselachogaleokranioleipsanodrimhypotrimmatosilphioparaomelitokatakechymenokichlepikossyphophattoperisteralektryonoptekephalliokigklopeleio-lagoiosiraiobaphetraganopterygon.

to: Μόλις Για.

from: Ioannis.

Good Luck, Good Health and Good Humor.

j-o-h-n Friday 01/21/2022 5:18 PM EST

[Justfor_]

Excellent! Now it's volume formula.

[Bubasurf6]

I have monthly PSA and other blood tests at UCSF's lab in San Francisco I have been getting the same test for over 7 years there The test they use is a Ultra sensitive PSA Performed using the Abbott Architect i2000 chemiluminescense method. Minimum detection limit of assay is 0.015 ug/L. I have also had two PSMA scans one 4 years ago while UCSF was conducting PSMA trials. At that time my PSA was 0.253. It didn't detect anything. Was in a triple drug trial for a year after that. PSA went undetectable until October 2020. MO wanted to wait till PSA was at least 0.5 to have another PSMA as the scan is more accurate at 0.5or more. I had PSMA Scan in October 2021 PSA was 0.822. Scan picked up 1 small Bone Met in lower hip bone. I received 5 SBRT radiation treatments to that area MO wanted 3 PSA tests 1 a month to observe how well the treatment worked Waiting for third PSA test on February 12 then meet with MO on the 15Th to discuss what's next. Most likely back on ADT. At time of second PSMA the doubling time was every 2 months. I got one PSA test at Lab Core that said I was less than 0.10 They said PSA was non detectable Went back to UCSF a week later The Ultra sensitive PSA result was 0.087 My Mo will only use the Ultra Sensitive test because he feels we can better the doubling time. Good luck

[farmanerd]

Having just a rough estimate of PSADT or even just an upper boundary of PSADT can give you enough information to start narrowing down diagnostic or treatment paths.

Question: My PSA history post RARP is a string of <0.1 measurements starting 1/19 until the final one at that level on 8/2/21. On 1/27/22 it's 0.21. What's a rough upper bound on my PSADT? Can a lower bound be estimated? Given the upper bound, how much waiting time before the next confirmatory PSA test?