One of my father’s doctors says that, even through his PSA is currently undetectable, we should do a PSMA scan with fluorid just in case. One of the arguments is that fluroid is less harmful for the body than gallium.
My father has a back pain which worries him.
The other doctor says the opposite and that it would be of no use and also riskful with the radiation.
Thankful for any insights and opinions!
I had a PSMA PET scan with gallium and it had absolutely no side effects. The advantage of this scan (which the FDA only approved some 18 months ago) is that it pinpoints every single cancer cell which radiates during the scan due to the gallium binding to the cancer cell). Subsequently the gallium naturally eliminates itself via urine.
The CT causes some radiation and therefore you should not get unnessary CTs. However, in the case of your father it will be necessary. You can take gallium or flouride it is almost no difference. Your father gets ADT so you do not have to wait for a certain PSA level. I had a successful PSMA PET at a PSA value of 0.09 while taking Degarelix.
He is of ADT for many months.
Hi. Did your psma scan detect anything at psa.09?
Yes, it detected the same affected lymph node mets that were detected with a previous PSMA PET/CT which was done before starting ADT.
And the ADT didn’t shrink it at or got ride of it?
I had six months of ADT between the PET scans. No, they did not shrink. I think it is not really helpful if the mets shrink by say 30%. When they become resistant, they will grow again to an even greater size than before.
First off, this is a grossly redundant subject as your father has already been exposed to "therapeutic" RT. Setting aside the targeted part of it, which is supposed to kill cancerous cells, there is a stray component that has already hit his entire body. I don't have exact quantitative figures regarding the latter, but my educated guess as a retired radio engineer tells me that it is many times more, compared to a single PET/CT. But you don't have to had my resume for landing to this kind of thought. Just notice how the RT technicians leave the gantry before the beam is switched on. If it were 100% targeted and absorbed without side lobes and reflections they could had stayed safely there. Consequently, in your father's case the proverbial phrase "the person that got wet in the rain doesn't fear it anymore" holds true.
But, I have investigated this subject for my self, being "dry" for now. The nitty-gritty of it has as follows:
The received irradiation has two origins, the external, due to the operation of the scanner and the internal due to the injection of the radio-ligand.
Fluoride has longer half life so your doc is generaly correct in claiming that it is less harmful than Gallium. It goes without saying that the comparison should be done on the same scanner because the sensitivity of the latter governs the quantity to be used. This is the most important parameter. Have the scan on a recent breed of scanner as this will lower both components.
A continuous motion scanner (Siemens marketing name mCT FlowMotion) is better than its earlier "Stop and Go" counterparts. A PET/MRI takes out of the equation the CT component altogether. More sensitive sensors need less radio-ligand for the same detection rate.
Finally, to give you an idea of the radiation quantity your father will receive, having done the math from published papers and taking as a reference the Canadian Safety Code, it is equivalent to 5 transatlantic air travels. In Youtube you can find a video featuring an Australian radiologist claiming that a Ga PET/CT induces less radiation than the combined effect of a scintigraphy (bone scan) and a CT. Do your due diligence.
Neither is harmful. Either should be used when needed.
I believe the PSMA PET/CT scans have the same or lower radiation exposure than a CT and Bone scan.
Cost of PSMA PET scan?
PSMA PET Scan Frequency?
Accuracy of PSMA PET scan?
PSMA PET scan results 
