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Differences between PSMA and CT/Bone Scan

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Posted 5/18/2022 1:35 PM (GMT 0)
Quick question, if a PSMA PET scan is done, does it still require a CT/Bone Scan? or PSMA PET scan will cover metastasis anywhere in the body?

I assume if PSMA Pet scan cannot be done (due to cost etc.) than perhaps a CT/Bone scan should be done to verify that is no metastasis.

Thanks,
Posted 5/18/2022 3:32 PM (GMT 0)
Pet scan is the best.. Psa should be at least .5 for it to get a good read....
Posted 5/18/2022 5:57 PM (GMT 0)
PSMA scan is waaaaaay more sensitive than CT/Bone scans.
As Steve0 said PSMA scan at about 0.5, but a CT or bone scan that low likely won't ever find anything.
Posted 5/18/2022 6:12 PM (GMT 0)
Upon diagnosis a bone scan and trunk CT are often done. Unless there are Mets that are sizable they usually don’t show anything, but are useful in setting a baseline for future scans. The CT is able to estimate the prostate size and shape. In my case the CT showed some enlarged lymph nodes and seminal vesicles. This information was useful in formulating the treatment plan.

Currently the PSMA PET scans are used with high risk diagnosis to look for the possibilities of Mets and after initial treatment that appears to have failed. If a small number of Mets are found targeted radiation treatment can be effective. If however numerous Mets are found, then treatment is usually systemic with several options.

Ray, it would help if you made a signature with your status so we have better information about your situation. Have you been diagnosed and treated for PCa?
Posted 5/18/2022 6:33 PM (GMT 0)
With regard to diagnosing the location(s) of recurrence after surgery, I'm not sure how the various radionuclides differ with regard to the minimum effective PSA. I remember one study of the 68-Ga-PSMA/PET found the "sweet spot" for PSA was about 0.75--you'd like the scan as early as possible (low PSA), but still want it sensitive enough to pick up small mets).

This recent study found the PSA cutoff was about 0.83 for distinguishing oligometastatic (usually 1-5 lesions) from polymetastatic disease:

Identification of the Optimal Cut-Off Value of PSA for Assessing Severity of Disease in [68Ga]Ga-PSMA-11 PET/CT Study in Prostate Cancer Patients after Radical Prostatectomy (2022)

(See the study for the different cutoff values for different purposes).

Medically speaking, there is a desire to have PSMA/PET scans replace the bone scan for diagnostic purposes, but unless costs come way down, I think insurers will balk at this.

Djin

Post Edited (DjinTonic) : 5/18/2022 12:40:18 PM (GMT-6)

Posted 5/18/2022 7:56 PM (GMT 0)
Based on what I have observed with my wife and my scans, bone and PET scans do not provide much resolution as they use specific tracers that “lights up” the things they are looking for (and many other areas) so a CT is usually done at the same time to check out the highlighted areas in detail. A PET machine usually has a CT with it whereas a bone scan is a separate deal.

The PSMA tracers do a better job of seeking out prostate cancer spread than normal PET and bone scan tracers.
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