metastatic retrocrural lymph node

[TomMaloney]

I had a PSMA scan on 12/14/2022 which identified a 4 mm reactive retrocrural lymph node.

Then I had a CT scan on 2/1/2023 which identified the same lymph node as 2.3 cm.

To me this is scary because it implies that volume doubles in 6 days and diameter doubles in 19 days.

Even scarier is that nobody at Dana-Farber put the 2 together.

Is this an emergency?

It sure has me depressed.

Thanks to all,

Tom Maloney

[Tall_Allen]

PSMA PET/CTs are not very good at estimating the size. The CT built into the PET scanner is not precise - it's there more for location than size. The separate CT scan is a better size estimate.

[TomMaloney in reply to Tall_Allen]

thank you TA, I'll be all over my MO and Dana-Farber to figure this out.

[Tall_Allen in reply to TomMaloney]

It's not really a mystery.

[Benkaymel in reply to Tall_Allen]

I thought the PET scan itself was more accurate/sensitive than a CT scan, if that's not the case, what is the benefit of having a PET compared to a CT?

[Tall_Allen in reply to Benkaymel]

The PSMA PET scan is able to find areas of PSMA uptake, which a CT scan can't do. When CTs are built into a PET/CT machine, the purpose of the CT is to give a guide as to where the uptake is occurring, within about 5 mm. A separate CT machine is much finer. Slices may be 1 mm apart.

[Benkaymel in reply to Tall_Allen]

Thanks Allen. It's interesting that a CT scan takes a few seconds while a PET takes 15 to 20 mins but is lower resolution.

[tango65]

The CT in the PET/CT is not a diagnostic CT scan. It may not be accurate to define with precision the size of the nodes

There is also the problem of the person reading the study. Many places have the PET/CTs read by nuclear medicine radiologists who are not specialized in reading or measuring CT studies.

CT scan reading is pretty specialized and in many places there are doctors reading only thorax, or abdomen or head diagnostic CT scans.

Next time ask your doctor to order the PET/CT with a diagnostic CT scan.

[TomMaloney in reply to tango65]

Thank you, great advice

[wilcoxsaw in reply to tango65]

Can this be done?

Wouldn't they have to do a diagnostic CT of your entire area that the PET CT was covering if they were both done at the same time to be of any value? Otherwise until the results of the PET CT were known , wouldn't the doctor be guessing as to which body area to order the diagnostic CT to examine?

[tango65 in reply to wilcoxsaw]

They do a diagnostic CT of the whole body first and then they do the PET study. The software allows them to superimpose both studies.

[wilcoxsaw in reply to tango65]

Great I will keep that in my memory bank thank you so much for the information

[TomMaloney in reply to wilcoxsaw]

Wow, you all have supplied very useful information. In the event, my MO said to wait and see what it looks like after the 2nd Pluvicto. She is a top shelf expert on prostate cancer; and she said: "That's what cancer does. It grows." Such a silly statement means that she is worried too, and that's all she had.