PSA for imaging to detect disease

[Jmr11820]

With all the rapidly changing advances in imaging, what is now the lowest PSA at which metastases can be detected?

[Justfor_]

At low PSA values it is the PSADT that becomes the dominant factor. For more info check this paper: ncbi.nlm.nih.gov/pmc/articl...

[Jmr11820 in reply to Justfor_]

thank you!

[Tall_Allen]

PSMA PET scans are not very good at finding metastases when PSA is below 0.5. There is a table at the end of this:

prostatecancer.news/2016/12...

[d3is4me in reply to Tall_Allen]

TA Do new digital PSMA F18 digital scanners such as GE Omni Legend show smaller lesions at low PSA Thanks in anticipation

[Tall_Allen in reply to d3is4me]

IDK. I haven't seen a comparative trial. I know the Siemens PET/MRI has better resolution than a PET/CT.

[Justfor_ in reply to d3is4me]

Digital scanners have more sensitive and smaller in size sensors. BUT, the detection rate is the product of 3 factors: 1) The quantity (apart from the type) of the radiopharmaceutical injected. 2) The scanning speed and finally 3) The sensitivity of the scanner. Some labs will lower 1) or speed up 2) and thus end up with images at par with older analog scanners. If 1) and 2) are kept the same, a digital scanner has a higher probability of detecting a spot of enhanced isotope concentration. Lesion size is basically irrelevant, quoted by people that don't understand the governing physics. It is the degree of spatial isotope concentration over the average that leads to a positive detection.

[d3is4me in reply to Justfor_]

Justfor Thank you

[Jmr11820]

Thanks Allen.

[OzzieJ]

My lymph nodes showed up on a PSMA scan at a size of approx 0.5cm and PSA of 0.6-0.8.

[Jmr11820 in reply to OzzieJ]

Wow! Quite low. Thanks for responding. All the best to you.

[bitittle]

I recently had a GA 68 PET Scan at UCSF. My PSA was 0.384. An obturator lymph node was detected with a size of 2mm. I question how they can accurately determine such a small size. Anyways there was a PSMA response. I have started with Orgovyx following in June with 25 pelvic radiation treatments with focus on the avid node.

This is a second recurrence 7 years after 38 radiation treatments to the prostate bed. My first recurrence was 2.5 yrs after my 2013 RP.

[Jmr11820 in reply to bitittle]

Thanks! Best to you.

[Justfor_ in reply to bitittle]

I will give you an analogue that you will be able to comprehend as you surely have come across it in your life:

Think back some decades and remember your film photo camera. You are about to take a picture that has the sun or a luminaire within the shooting frame. No matter what you do it will stand out from the rest of the objects that are just reflecting the ambient light falling upon them. If you zoom out, its size on the picture will be reduced, but nontheless it will still be there. This light source in the setup is the equivalent of the radio isotope in the body. You can try tinkering with the camera's shutter speed (the equivalent of the PET scanning speed). The whole picture may end up sub-exposed (darker), but the sun or the luminaire will still stand out from the background. Lastly, you can try tinkering with the sensitivity of the camera (the equivalent of the PET scanner's sensitivity). This can be effected either by employing a film stock with a higher ASA rating (speedier) or opening up the iris diaphragm. In the former case the picture's grain will become more prevalent and in the latter the depth of field will be reduced. Nothing can mask the light source!

[Jmr11820 in reply to Justfor_]

👍like the analogy or analogue. Makes sense. Takes me back to my TriX Pan days.

[NecessarilySo]

I seem to be able to "feel" metastases long before they are visible on scans, at least some of them. Scans help. Lycopene intake reduces their pain. They come and go with various treatments.

[Hidden]

After 19 years of Persian experience, the answer lies with your Medical Oncologist who has the knowledge and skills necessary to treat. If one is looking for distant spread when PSA rises from undetectable to 0.5 and beyond, it would be prudent to have a PSMA PET Scan followed by a comparison Nuclear Bone Scan m. And finding nothing, Abdominal MRI with a Prostate Protocol. Again finding nothing, you may have BPH and a high grade UTI.

Your Medical Oncologist diagnosis is vital. Best wishes…….

Gourd Dancer

[Jmr11820]

Appreciate your response!

[ron_bucher]

My oncologists use 0.20 as a rule of thumb, but my radiation oncologist heard from a doc at Mayo Clinic that they have seen PSMA positive results at lower PSA values, even some undetectable PSA.

Every case is unique, so beware of cookie cutter answers for any case.

[Jmr11820]

undetectable meaning <.1?

[RMontana]

Check out this post if you have not seen it...I would start at 0.2 and get as many as needed, when and where required, as PSA increases...Doctor want to play the 'efficiency' game and have you wait for PSA to be high enough to 'guarantee' the scans will show something!!! What? That is like your mechanic saying; 'Hey, its a small knocking noise now, but just drive the car until we can see smoke and fire coming out, then well fix it...' Right...do that on their car! Get a scan at 0.2 and then get them as you think you need them...saw a case study, which I will post, where a patient got 3 scans, starting at 0.2, until he found the spot with cancer...pissed off his doctors, but I agree with his approach...Rick

healthunlocked.com/active-s...

[Jmr11820]

really good advice. thanks!