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PSMA in Prostate Cancer


Kristie L. Kahl: Can you tell us about the approval for gallium-68 PSMA and prostate cancer approved in 2020?

Raoul S. Concepcion, MD, FACS: Yeah, so basically what PSMA scanning is, it’s a biomolecular scan that just received FDA approval. So what makes this important is that this is yet another radioisotope labeled biomolecular scan that that is now going to be available to the urologist as part of their armamentarium. And the unique thing about this particular approval is that it is going to be approved for patients who are suspected of having metastatic disease. There are a couple of other biomolecular agents that are out there on the market, but that is the current approval. It's for any prostate cancer patient that is suspected of having metastatic disease. And, Chris, I know you there's also some little caveats that go along with that, though, however.

Christopher M. Pieczonka, MD: First and foremost, there was a prospective study comparing this new agent PSMA scanning with the gallium PSMA scanner with 18, f glucose alvine. And that was in The Lancet Oncology from about a year ago. And I think that that's sort of set the standard to really look at as a comparison between the new and the old. So, you know, the fucose Sylvain scanning has been around for a while. I think its limitations have been, in some ways, primarily based on insurance coverage, so to Medicare, easy to get sort of traditional insurance and hard to get done. But I think that this is just the advent of really new and exciting imaging technology there.

There are some definite advantages for the PSMA scanning. I think the technology is just a little bit better. I think that part and parcel to that is that prostate cancer cells have a tendency to overexpress PSMA. And so there's a much better sort of ratio of PSMA to the background, there's background noise with any of these pet scanners. So the PSMA, I think is a little bit better than the fluconazole scanning. I think part of the what's interesting for the audience to hear about is that although there's FDA approval, this is not going to be something that you're going to order tomorrow, you know, Raoul, tell me a little bit about kind of the limitations we'll have with getting these tests ordered.

Raoul S. Concepcion, MD, FACS: Yeah, I think that's an important point. And I again, I think the viewing audience, hopefully you picked up on this, but right now, the approval is only for 2 institutions. It's only approved for UCLA and UCSF. So it's not like this is an across the board approval for anybody that's got a PET CT scanner. So that's the first one. I think I think on the positive side, like I mentioned, it is approved for anybody who is suspected for metastatic disease. So it could be the newly diagnosed, high-grade, high-risk patient with a high Gleason group 4 or 5 that we know historically is generally going to be at a high risk for failure and we obviously worry about de novo metastatic disease, but at the same time it also is going to be approved as in the treated as in the current scans for patients who have been treated for prostate cancer and have a recurrence. So as my illustrious colleague Dr. Pieczonka just said is that 1 of the scans that's currently approved is fluconazole, which is a synthetic amino acid and the trade name is called action and scanning. There's also a C-11 coline scan, which is only really present in a couple of institutions because the half-life is so short and I think it's important for the audience to understand that all these next generation scans. They basically are using a radioisotope. So in this particular recent approval, it's gallium-68 in the abdomen scan, as Chris mentioned is fluconazole. That's it. That is actually good. It's bound to florian. And then also and Chris, I'll let you comment on that there was a newer scan that just got priority review, which is a fluorinated scan with using yet another PSMA ligand called PYL. And, Chris, I know you've got a little bit of knowledge about that particular trial.

Christopher M. Pieczonka, MD: So kind of a couple things. I think that the thing about PSMA scanning is ex-US people use this all the time. And in the US, essentially, no one uses it and 1 of the rate limiting factors on at least the gallium scan which is only approved by an institution, sort of the code for making the product is available sort of for public consumption, the rate limiting factor is going to be the half-life of the gallium and the half-life is so abrupt that if you're not in an area that has a cyclotron that can make the medicine you're not going to have access to the scanning, you know, in either case, so that happens to be the case where I am now. I can get glucose alvine comes to me from a couple hours away, we're not going to get gallium until somebody turns the switch on to make it get back to some of the other agents that are coming as this PYL compound is something that has priority review, not FDA approved yet. There was a study called the CONDOR study, like the bird that really looked at the sort of benefit of this type of imaging agent. And what's going to end up happening is in the next year or 2, we're going to have bunches of different companies coming out with other ligands that are going to look to bind to PSMA. And there's going to be certain nuanced benefits of different ligands. Gallium is not going to be the 1 I think that's going to really carry the weight long term, because that's going to be a diagnostic agent only, but some of the new ones that are coming out, potentially are going to be able to be both diagnostic and therapeutic. And we call that theranostic. Maybe not in 2021, maybe in 2022, we're going to have things that are going to be able to detect metastases sooner and treat them with a radio-guided pharmaceutical similar to how we treat bone metastasis with Xofigo (radium Ra 223 dichloride).

Raoul S. Concepcion, MD, FACS: Chris, those are great points. And I think I think it's important for the audience to understand this is why, you know, again, as we pick topics to end up the year that are significant is that this really, in my opinion, and excuse the overuse term, I mean, it is potentially a game changer. Number one, if it's going to be used again, as we discussed, and if other agents get approval for this to be used in patients with suspected metastatic disease, all of a sudden, these scans are going to be used, potentially in staging of the newly diagnosed patients, which will now bring in this whole concept of all metastatic disease, which historically, we've classified as patients who are newly diagnosed and have less than 5 metastatic sites. With the advent of local therapy, radiation, and systemic therapy. Now all of a sudden, these patients really should be considered for multimodality treatment. And I think that that becomes a huge paradigm shift on how we manage newly diagnosed patients. And to Chris's point, I think the other big thing is that ultimately, what he was speaking with is, is really this concept of theranostics, which is taking these radio isotopes, and now you're essentially attaching a radiopharmaceutical. And the one that's kind of been studied in phase 3 is lutetium. And that's a beta emitting particle. And, and once again, this allows us to have the proverbial yet another arrow in our quiver, if you will, to essentially be able to treat these late-stage castration resistant prostate cancers. So I think for 2021, when these other agents get approved, you're going to see uptake, you're going to start to see I think, some real changes on how localized and advanced diseases managed.

Christopher M. Pieczonka, MD: You know, I think one thing that kind of comes to my mind and I try and impress this on some of my younger partners coming in, is that sort of the era of radical prostatectomy route when you and I did our training, we did open procedures, then this robotic thing happened after we got done with our residency. We used to operate on Gleason scores all the time, and we don't operate on them anymore. And you know, I'm conceiving a new world where we have access to these new PSMA scans. And we use them for screening and high-risk patients that are going to be found to be metastatic that jury will be out if you still operate on those patients. or not, you know. So I think that the reason that this is so, you know, intriguing for urologists is that, if we're not facile with the technology for not doing this, then we're going to end up losing these patients not being able to treat them. So the goal for all of us is to be educated, understand the disease process so that we control the patients, just like the GYN oncologist do rather than getting a patient with metastatic disease and referring them outside to, you know, to the medical oncologist.

Raoul S. Concepcion, MD, FACS: And, you know, I think probably to close this portion, I think what you're saying, Chris is really important. Are we going to get away from radical prostatectomy? Probably not. But as you also know, you and I have both been in discussions with other trials, where we're looking at adding some of these systemic agents before surgery, trying to downstage we've looked at that in the past with ADT, but now that we have some targeted agents now that we understand the mechanisms behind what drives, especially higher grade prostate cancer, you know, the understanding of the molecular drivers, not just based upon Gleason, really becomes important. And again, now we have all these different mechanisms, these mechanistically different agents. And the question really is: Where do we use them early in the process of localized disease? You know, we're getting a better grip, we're getting more agents, obviously, in the advanced disease. So again, I think this is a significant breakthrough. And I think all of us are looking forward to seeing how this plays out in 2021.

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