Advice to guide my scan choice

[lokibear0803]

Briefly, I’m officially “biochemically recurrent” though small lymph node mets (locoregional, as I understand) have been found (never larger than 6mm) both through removal via lymph node surgery after a C11 PET in 2014, and after a PSMA-11 in 2018 (these were radiated). Mets never seen on standard scans (CT, MRI, bone). PSA most recently mid 5’s since the 2018 radiation, DT is about 5 months (and slowing down, for what that’s worth).

My question is around anyone’s thoughts on a choice I can now make between two different scan trials out of state: one is the 18F-DCFPyL, the other combines PSMA-11 (R2) and DOTA-NeoBomb1 (which I think is the same as Bombesin?). So the first choice (basically, Pylarify) “might” be more sensitive, logistics are easier (just one scan) and overall radiation exposure is less. But the R2 + NeoBomb “might” detect more stuff as per the gastric-peptide affinity of the NeoBomb; but logistics are harder (must wait 24 hours b/w scans) and radiation exposure is about twice the PyL alone.

When I say “logistics”, I mean number of days of lodging; I realize this should not be a deciding factor unless all else is equal. but if we think the combo will give me more information, the logistics are a moot point.

I mention radiation exposure only since the followup treatment may be EBRT...am I conflating radiation exposure concerns here? i.e. perhaps the scan radiation doesn’t contribute in the same way as any EBRT to an annual maximum dose.

From the “PET Scans for PCa” article in Prostate Cancer News (dated Dec 2016, though possibly updated since?), it appears PyL is more sensitive (3rd best) than PSMA-11 (5th best), though I didn’t see quantitative comparisons on sensitivity/specificity, i.e. it may not be significant enough of a difference to *strongly* favor PyL over PSMA-11 + NeoBomb, again especially since the NeoBomb might yield additional information.

Regardless, thank you in advance for any thoughts.

[Hidden]

Just out of curiosity If you already know its in the nodes, do you plan on whole pelvic radiation? Have you had that already?

[lokibear0803 in reply to Hidden]

Yes, I had some targeted EBRT done based on the location of mets. I don’t recall hearing the phrase “whole pelvic” at the time; perhaps there was concern due to previous surgery in the area? proximity to GI tract? Not sure. Bottom line it was apparently something that bought me some time.

[Hidden in reply to lokibear0803]

If in the process of removing the prostate they had found a hot node, I believe they would have recommend something like 2 years of some sort of hormone therapy combo and whole pelvic radiation....with the intent of wiping any residual out. So here you are, with identified hot nodes, no seen bone mets. maybe that same kind of systemic, crushing blow, kind of treatment really could do wonders for you. Think about that, like in a positive way. Good luck.

[Tall_Allen]

I think it was a mistake to have only the positive lymph nodes radiated. Where there's some cancer in the pelvic lymph nodes that you can detect, there is certainly a lot more that is too small to detect with ANY method (even the double PET scan you are contemplating). The detection limit of any PET scan is 5 mm and most of the cancer in the LNs is a lot smaller than that. The question you should be asking to your RO is whether you can still have whole pelvic radiation. My guess is that you can, if they avoid the LNs previously irradiated.

A recent study at Mayo found that men who had only a few nodes radiated didn't do as well as those who had them all irradiated:

prostatecancer.news/2020/12...

[lokibear0803 in reply to Tall_Allen]

Thanks, I’ll bring this up with my MO. But my impression was that once a given area receives any radiation, that they can no longer radiate there again. I may have misunderstood.

[Tall_Allen in reply to lokibear0803]

It depends on exactly what was radiated previously.

[lokibear0803 in reply to Tall_Allen]

Regardless - do you have an opinion on which scan trial would be “better”? I know this question may not yet have a definitive answer.

[Tall_Allen in reply to lokibear0803]

I think that if you want to find smaller LN metastases, get the Combidex MRI only available at Radboud University in Nijmegen, The Netherlands. But I think you are wsting your time playing whack-a-mole. Systemic treatment will lengthen your life.

[MateoBeach]

Pylarify PSMA would be a good choice: sensitive, available and will also indicate if Lu-PSMA might be of benefit when available. In the Meantime definitely pursue extended field whole pelvic LN RT. They have shown that repeat irradiation with SBRT can be done after pelvic RT fails, so why not the reverse? Worth discussing. Better than whack-a-mole.

Good luck. 💪💪💕

[lokibear0803 in reply to MateoBeach]

Wouldn’t the PSMA-11 also show what’s needed for Lu177?

[Blackpatch in reply to lokibear0803]

Maybe, but Lu is only available in trials for people at your "early" stage - there really isn't a sound basis to believe that Lu could be on the horizon for you yet, so I wouldn't rush to be scanned for that purpose.

PSMA PET scans are used routinely in Australia because they have been available for about 5 years (i.e. there isn't the agonising over "should I/shouldn't I" that seems to abound in the States at the moment). If you were here, I think you would be having a straightforward 18F-DCFPyL scan to see where the hot spots are. But the key driver for your decision-making should be the rate of change of PSA... 5 months DT is a bit too fast, let's hope it keeps slowing down - that's what I would be watching most closely.

[lokibear0803 in reply to Blackpatch]

Hi Blackpatch, do I read from your comment that you live in Australia?

[Blackpatch in reply to lokibear0803]

Yep... Melbourne.

[lokibear0803]

My thanks to everyone for their thoughts.