Not correlated by CT????

[Break60]

I had a PSMA ga68 CT pet scan resulting in radiotracer uptake in rib and scapula “ not correlated by CT” . What does this mean?

Bob

[Tall_Allen]

It means the PSMA scan detected mets that were not large enough to see on the CT scan.

[Break60 in reply to Tall_Allen]

Thanks TA. How do I know they’re not false positives?

Bob

[Tall_Allen in reply to Break60]

The only way to know with certainty is a biopsy, and with nothing on the CT, it would be hard to biopsy anything. They are fairly common sites for bone mets. False positives in bone are uncommon. The question is what would you do differently? You should be on systemic therapy anyway.

[Break60 in reply to Tall_Allen]

I am on systemic therapy. But I would add sbrt .

[Break60 in reply to Tall_Allen]

TA

You say false positives in bones are uncommon. That’s comforting. So if there is uptake of the radiotracer in the bone it means it’s undoubtedly malignant ? Is there such a thing as benign tumor in bone?

[Tall_Allen in reply to Break60]

Not "undoubtedly" but probably. The specificity of the PET scan is 88-100%. In the following study they confirmed the PET findings with biopsies and found that 100% of the PET-positive areas were also biopsy positive:

ncbi.nlm.nih.gov/pmc/articl...

[Break60 in reply to Tall_Allen]

TA

Thanks for the link. I found it interesting that UCSF had no strings attached to the trial and they only charge for the radio tracer (<$900) whereas MSKCC charges for the whole loaf ($~7600)

Bob