PSMA effectiveness in diagnosis

Do you mean for a first diagnosis? It is meant to diagnose metastatic spread. It cannot replace a needle biopsy of the prostate.

Rob55. what about bone metastasis?

@rob55
No problem picking up bone mets on me.

@rob55 Should work for bone mets as long as the cancer is psma avid.

Yes, it can find bone Mets and some doctors have said it replaces a bone scan and CT scan. The issue is that it cost a lot more to do a PSMA PET scan then it does to do a bone scan and CT scan scan, So many doctors still stick by them.

It only detects areas which are PSMA avid, and not all cancer cells are. So it cannot replace all other diagnostic tests. It is particularly good at finding bone metastases on the spine and elsewhere IF they express PSMA.

@jeffmarc Please clarify for me the difference between PSMA PET vs. CT vs. PET CT. Sorry to be do uninformed on the basics.

A CT scan can find some metastasis, it works better if you have a previous CT scan to compare with. A bone scan can find some metastasis in the bone, but it is not real accurate Compared to a pet scan. Both of these tests are much cheaper than a PSMA Pet test. They can also be done when the PSA is very low, Where a pet scan might not show anything.

My understanding is that a PSMA-PET scan isn't very effective if your cancer is already suppressed by ADT and/or ARSI: dormant cancer cells just won't take up much PSMA. So for people like me, with long-term mCSPC, a combination of bone scans, CT+contrast, and MRI+contrast is more telling (since they can see lesions and bone damage even if the cancer is currently dormant).

If my cancer ever becomes castrate-resistant and "wakes up," then PSMA-PET can spot tumours too small to show up on other types of scans (along with aome spots that aren't cancer at all).

And even with PSMA-PET, you still get CT or MRI as part of it, I think (maybe it's built into the same machine?), because PSMA-PET just shows blobs; you need something to draw the background bones, muscles, organs, etc. They're both greyscale, but the PSMA-PET "blobs" will be artificially colourised to distinguish them from the background.

And of course, no scan replaces a biopsy; you could oversimplify and say that scans just show them where to stick the biopsy needle. 😉

(p.s. layperson writing here; verify with your onco)