Why the need for an FDG scan in addit... - Advanced Prostate...

Advanced Prostate Cancer

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Why the need for an FDG scan in addition to a PSMA scan?

Schwah profile image

I have had three negative PSMA scans at UCLA in the last year. A number of those more knowledgeable than I, on this site whom I greatly respect quite, often suggest an FDG scan in addition to a PSMA Scan to look for any cancer that does not express PSA. After my last scan, I emailed Dr. Czernin at ucla (head of the imaging division at UCLA) to ask if he thought I needed any additional scans to search for Non-PSA expressing lesions. He replied as follows:

“....the PET/Ct scan not only includes the PSMA scan but also a CT scan. The Ct scan is reviewed for lesions and masses in any tissues (lymph nodes, bones, lung, liver, etc) regardless of PSMA findings. If nothing shows up on the CT and PSMA scans it is very hard for me to imagine that the axumin and the FDG scan can show anything more relevant.

Hope that this helps,

Johannes Czernin“

I am having difficulty reconciling this doctors response with what I have read on this site about the need for the additional scan(s). I would love some those who disagree (or agree ) with his response to explain their thinking.

Schwah

41 Replies

1. Tall Allen brought up the fdg scan here.

I by default sort of trust him over most docs, unless or until proven wrong.

I would recast the question to: would there be any harm to doing an fdg, other than you aren't set up to do them.

2. "three negative PSMA scans at UCLA in the last year"

There is some reason you are being prompted to do all these scans.

Go get a second opinion from a place that regularly does fdg scans.

Seems to me this is simple logic. If you think there is something there, and your tool keeps coming up negative, why on earth would you not change tools.

I think this rutted thinking is a good reason to change docs. You are getting treated out of a cookbook.

Go try some different recipes if the current one is being repeated over and over. Get a few second opinions.

Ask tall Allen for a few local recommendations.

Schwah profile image
Schwah in reply to cesces

Thanks. I am discussing with below.

Schwah

Dr. Hofman from Melbourne came up with adding a FDG scan to a PSMA scan. He stressed the importance of this at the APCCC conference last year. But I think, it makes sense for Dr. Hofman to exclude patients with a positive FDG scan from his PSMA trials. This way he can report better results for the Lu177 treatments. He gets about 10 to 15% better results than those reported by the trials which did not use an FDG PET/CT to exclude patients. For the patient, it could still make sense to remove e.g. 70% of his metastases and control the remaining 30%, which are PSMA negative, with ADT or SBRT.

If you do a PSMA PET/CT the CT is usually used to get additional information for the lesions which show up as PSMA positive. It is not analysed as a whole-body CT, at least the RO does not spend a lot of time on that. I agree that an Axumin scan or FDG scan are less sensitive and if the PSMA PET/CT did not show anything, these will usually only show lesions at very high PSA values then. The trials by Dr. Hofman included patients who had failed most treatments before and therefore had very high PSA values.

A Choline PET/CT is more sensitive for prostate cancer than an FDG PET/CT. However, its sensitivity is reduced while you are having ADT. I had two negative PSMA scans but have a rising PSA value. Before I start with ADT again, I will get a Choline PET/CT when the PSA value gets to 3 ng/ml. A Choline PET/CT is offered by a clinic nearby and I hope this will clarify the reason for the rising PSA value. In the US Dr. Kwon offers a Choline PET/CT.

You can read about it here:

prostatecancer.news/2019/12...

Was there something in it you didn't understand?

My friend had some PSMA avidity, but he had a lot of FDG avidity (both PET scans at UCLA). Based on that, Jeremie Calais (UCLA), Michael Hoffman (Peter Mac, Melborne) and Matthias Eiber (TUM, Germany) had a conference call and decided that Lu-177-PSMA treatment would not be in his best interest.

cesces profile image
cesces in reply to Tall_Allen

Tall_Allen

1. So what is your opinion about using either a Choline PET/CT or Actetate PET/CT scan as substutes for an FDG scan?

Other than the limited availability of Choline PET/CT and Actetate PET/CT scans.

2. What about substituting an Auximin scan for the FDG scan?

Tall_Allen profile image
Tall_Allen in reply to cesces

You are talking about a completely different thing than Schwah is. If you are pursuing PSMA-targeted therapy, it is FDG that you should get in addition to PSMA. Cancer cells may loose expression of PSMA and start to metabolize glucose as they progress. Choline, Acetate, and fluciclovine do not pick up the late stage progression.

cesces profile image
cesces in reply to Tall_Allen

"Choline, Acetate, and fluciclovine do not pick up the late stage progression."

Thanks. I think that is important to know.

hansjd profile image
hansjd in reply to Tall_Allen

Hi Tall_Allen. What is your opinion on getting a dotatate PET scan as well as an FDG PET?

Tall_Allen profile image
Tall_Allen in reply to hansjd

Only if you have a secondary GI cancer or IHC shows expression of somatostatin.

hansjd profile image
hansjd in reply to Tall_Allen

Sorry, but would it not also help to give a better picture as to whether any neuroendocrine PC may have developed. My understanding is that the two scans together (FDG and dotatate) give a fuller picture. Thinking not just for possible Lu 177 treatment, but more precise treatment in general. Thanks

Tall_Allen profile image
Tall_Allen in reply to hansjd

No. Neuroendocrine prostate cancers, for the most part, do not express somatostatin. Rarely, they might - that is a rarity on top of a rarity. That is easily ascertained by IHC.

hansjd profile image
hansjd in reply to Tall_Allen

Thanks very much.

I think CT scans are not as sensitive or specific as a PET that shows metabolic activity. So if the prostate cancer has switched to using glucose as a primary fuel, which can happen when it becomes more aggressive, and looses its PSMA expression, it is more likely to show on an FDG PET than a CT, and you will know that it is cancer, whereas it is not always clear with a PET if a lesion is cancer or something else.

These studies report that for prostate cancer a Choline PET/CT is better than a FDG PET/CT . Therefore I prefer a Choline PET/CT.

[11C]choline-PET seems to be useful for re-staging prostatectomy cases with increasing serum PSA levels. It is superior to [18F]fluorodeoxyglucose-PET

pubmed.ncbi.nlm.nih.gov/126...

When compared to metabolic based imaging techniques with FDG, choline PET/CT was superior.

tau.amegroups.com/article/v...

cesces profile image
cesces in reply to GP24

But Tall Allen says: "Choline, Acetate, and fluciclovine do not pick up the late stage progression."

GP24 profile image
GP24 in reply to cesces

Schwah and I are not late-stage but rather look for small mets while being hormone-sensitive. According to the studies I mentioned, in this situation a Choline PET/CT is superior to an FDG PET/CT.

Tall_Allen profile image
Tall_Allen in reply to GP24

I agree.

Schwah profile image
Schwah in reply to Tall_Allen

Yes but a PSMA scan is superior to both , correct ?

Schwah

Tall_Allen profile image
Tall_Allen in reply to Schwah

Yes, of course. Hopefully, the DCFPyL PET will be approved soon.

cesces profile image
cesces in reply to GP24

So complicated.

BTW- why were you asking? You wouldn't be asking unless you were contemplating a PSMA-targeted therapy? If so, which one?

GP24 profile image
GP24 in reply to Tall_Allen

If the PSMA scan is negative it makes no sense to get a PSMA targeted therapy. I hope if the Cholin PET/CT detects metastases I can get them treated with SBRT.

As you know, Dr. Kwon did that and presented it in this video: youtube.com/watch?v=Nkqizmv...

Tall_Allen profile image
Tall_Allen in reply to GP24

Idiotic video, imho. The question was for Schwah.

Schwah profile image
Schwah in reply to Tall_Allen

My real thinking Tall Allen, is as follows. After 21 months, I’m on a “vacation” from lupron and Zytega for about a year now. Since My vacation started, my PSA has slowly gone up to its most recent 3.6. However, as you may recall I still have 60% of a larger size prostate (after focal chryo almost 10 years ago) with indications of Prostatitis which could be the reason for the psa.. Although previous scans found three mets, none (including two MRI’s) have indicated any more disease remaining in the prostate , at least that can be seen. So my thinking has been that I will do the PSMA tests every six months to determine if there’s any progression that would necessitate my going back on the drugs. Since all three PSMA tests have been negative with “no changes“, I had in the back of my mind that perhaps some non-PSMA avid lesions may exist which Are not being picked up with the PSMA scan. Dr. Czernin as you saw said not to worry, but I respect your opinion a great deal and therefore I worry I’m missing something. Hope that makes sense.

Schwah

Tall_Allen profile image
Tall_Allen in reply to Schwah

That article and the need for an FDG PET only applies to those interested in PSMA-targeteed therapy. That has nothing to do with you.

If your first 3 metastases showed up on a PSMA PET/CT, there's every reason to believe the next ones will too. If they are not big enough to be detectable with the CT, you can probably stay on your vacation.

Schwah profile image
Schwah in reply to Tall_Allen

Thx so much TA. My 3 mets were actually detected in Phoenix Arizona on another non FDA approved C11-acetate test that Dr Scholz said at the time (before PSMA testing was available) was the state of the art. I assume that does not change your thinking?

Schwah

Tall_Allen profile image
Tall_Allen in reply to Schwah

That's fine. Until late stage in their evolution, prostate cancer feeds primarily on fats, so the acetate and choline PETs are fine. 90+% of metastases will show up on PSMA.

UCLA and many other centers doing PSMA PET/CTs can do FDG PET/CTs for prostate cancer and for many other cancers, lung, colon cancer etc.

PC that is highly treated with chemo and anti androgens may not express as much PSMA as cancers not treated with these drugs, except for short time ADT or enzalutamide. This has been shown by studies done by Hofman et al:

euoncology.europeanurology....

I believe we are confounding diagnosis of metastasis by CT scan and PET/CT vs diagnosis of the PSMA expression by the cancer.

Dr Czernin is saying :" If nothing shows up on the CT and PSMA scans it is very hard for me to imagine that the axumin and the FDG scan can show anything more relevant."

I think he is right but what he is saying does not have anything to do with the amount of cancer in the lesion expressing PSMA. The metastasis could be diagnosed by the PSMA PET/CT scan and by the CT scan but most of the metastasis may not express PSMA when compared with a FDG PET/CT scan (see fig 1 in the article listed above). Cancers with this type of lesions will have a poor response to Lu 177 PSMA therapy.

FDG PET detects PC due to sugar uptake - metabolic labelling whereas PSMA PET uses a radiolabelled ligand that targets the surface PSMA molecule present on some PC cells. Clearly if a PC is predominantly FDG+ but less so PSMA + then there would be little use in using PSMA targetted approaches (as with Lu177 or the like).

Often both tests are used (as with me) when there has been a history of previous Lu177 therapy where you would expect many PSMA cell clones to be destroyed.

Is there a reason for getting 3 PSMA scans in one year? For those of us with no direct access to such diagnostic tools...this seems to be an extreme amount of resources being duplicated. I'm wondering what are the clinical requirements for using such a valuable and expensive resource repeatedly in a year?

Schwah profile image
Schwah in reply to JRPnSD

Yes there is my particular situation. I originally had focal cryo-procedure which left me with 60% of a prostate. Therefore as I try to determine when to end my drug vacations, I cannot rely solely on PSA (Since my remaining Health prostate tissue would be expected to produce some PSA). Therefore I am going to do PSMA tests every six months to help me determine progression and thus the time to end my vacation. Interestingly this is a negative about focal treatment that I never considered. Schwah

JRPnSD profile image
JRPnSD in reply to Schwah

Thank you. I wish you well on your journey.

Tall_Allen profile image
Tall_Allen in reply to Schwah

I may save this for the next time a man tells me he is considering focal ablation.:-)

Schwah,

Was your focal cryo doctor Dr. Onik? If so, did he use the immunotherapy drugs as he has done with many others?

Schwah profile image
Schwah in reply to LeeLiam

No it was Dr Bahn in Ventura county. I believe he’s been doing chryo (especially focal Chryo) longer and on more patients than just about anyone. No immunotherapy tho. What was the thinking there ?

Schwah

Tall_Allen profile image
Tall_Allen in reply to Schwah

You are talking about different things. Onik was using cryo to ablate metastases in order to release antigens and get an immediate immune response that he amplified and kept going with immunotherapy.

Schwah profile image
Schwah in reply to Tall_Allen

What’s your thinking on the potential efficacy of his treatment TA?

Schwah

Tall_Allen profile image
Tall_Allen in reply to Schwah

It doesnt surprise me that he is able to elicit an abscopal effect with cryo, as has been done with radiation (see below). If he has anything worthwhile, I hope he will publish. Youtube is not the way to do medical science.

prostatecancer.news/2016/08...

Dr. Onik has achieved complete remission in some metastatic patients by injecting three immunotherapy drugs after freezing a tumor. Apparently freezing the tumor does not destroy it like radiation or heat but kills the cancer. Its like if you heat an egg and then open it, it looks completely different. But if you freeze an egg, thaw it and open it still looks like an egg, but its lifeless. The immunotherapy drugs combine with the dead tumor cells show the immune system what the cancer looks like and to achieve an abscopal effect (thanks to TA for teaching me that term). He published a paper last month: cancerres.aacrjournals.org/...

His website is garyonik.com.

Schwah profile image
Schwah in reply to LeeLiam

Interesting. So you had mets? But he treated only your prostate ? Or did he treat the Mets directly ? How long ago? What was your Gleason? How many mets and where? How long ago? Thx

Schwah

I have not been to see him (yet). I have been following his protocol since it was presented by Dr. David Bostwick in a support group meeting I went to in 2016. I am having a recurrence but it seems to be only local (according to my Axumin scan). I will have a rhPSMA scan in three weeks. If it shows only local, then I will probably do FLA or ultrasound (TulsaPro). If it shows nodal involvement, then I will see Dr. Onik. You can see some amazing videos if you Google gary onik youtube.

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