I have heard in this forum that both a PSMA and FDG scan should be performed to determine if your cancer will respond to LU-177. With the hoped for answer being your PC has all or mostly PSMA.
I recently spoke with my MO who just began Pluvicto treatments a few days ago and he says the FDG isn't needed. That the CAT scan portion of the PSMA PET scan also identifies what cells are not PSMA active and shows the heterogeneity of the PC.
Is he correct?
No, he is not correct that CT scan can detect all metastases that don't show up on a PSMA PET scan. CT can detect the bigger ones. It isn't required to get Pluvicto, it's just prudent.
Here's the data you can email to him:
ncbi.nlm.nih.gov/pmc/articl...
euoncology.europeanurology....
FDG could give you some heads-up on neuroendocrinization - especially for CRPC and mCRPC, some mets will not show signal of PSMA but they are just there and you have to mind for that.
Hello Mac,
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j-o-h-n Tuesday 07/12/2022 6:46 PM DST
I think "needed" is too strong a word. Perhaps "suggested by some" is more accurate?
Not trying to be cynical, but it seems unlikely that Novartis would be seeking ways to further restrict numbers of men who might seek to qualify for the treatment. Certainly they want to exclude men for whom there is no chance of Pluvicto working (i.e., with no PSMA expression), but they would not want to limit treatment only to the men who are BEST-suited for good responses.
No, it is not needed.
The Hofman’s group in Australia started to use it in a randomized control trial to select patients who will benefit more from Lu 177 PSMA treatment. For example, if a FDG PET/CT showed tumors which were PSMA negative those tumors will not be treated by Lu 177 PSMA treatments and those patients were not admitted to the trial.
Other criteria to select patients had been used in trials such as mets with SUV values similar to the liver or at least one met with a SUV of 20 or more. These criteria eliminated all patients which did not have metastases with those values.
More recent they are concentrating the selection of patients using the whole body mean SUV value (do no ask me how they can calculate this value) and based in this value decide which patients will benefit from Lu 177 PSMA treatment.
If one has a cancer with low PSMA expression (mets SUVs less than the liver) , a FDG PET/CT may be useful to make a final decision about treatment with Lu 177 PSMA, since there may be mets which are not seen in the PSMA PET/CT and appear in the FDG PET CT.
Other criterium which could eliminate patients for Lu 177 PSMA treatment is diffuse bone marrow infiltration in a PSMA PET/CT.
If these patients are treated with Lu 177 PSMA, many normal blood cells in the bone marrow could be affected by the radioactivity of the Lu 177 PSMA attached to cancer cells in the proximity and make the hematological problems even worse.
The bone marrow of these patients could be affected less if they are treated with Ac 225 PSMA since the radioactivity of alpha particles travels less distance than the beta particles of the Lu 177.
SUVmean is derived with the aid of specialized software. The radiologist spots and marks all the hot areas. Contouring follows, I believe, at this moment done manually and the hope is that in the future machine learning will undertake this tedious job. Then, it is easy for the software to read the SUV values of all inclusions and calculate a mean value. This metric is by far more representative of the total burden compared to SUVmax.
For the trial I am involved with a PMSA, CAT and Bone scan were performed. There were mets on L4/5. Five sessions of radiation were prescribed prior to the trial. I have not seen any of the scans but was told my PSMA expression was over 95%.
Looking for LU-177-PSMA treatment in Germany
How is PSMA PET scan being used in your experience?
Overall Survival With [177]Lu-PSMA-617 vs Cabazitaxel in Metastatic Castration-Resistant Prostate Cancer
When they speak of the trial Lu-177 scan, are they referring to the Axumin scan? 
"Early initiation of Lu-177 PSMA radioligand therapy prolongs overall survival in metastatic prostate cancer"
