Phillip Koo: Hello, my name is Phillip Koo and welcome to a very special segment on UroToday where we have with us Dr. Juan Carlos Galvis, a radiation oncologist who subspecialized in prostate cancer and is also the head of radiotherapy at the Clinic Los Nogales in Bogota, Colombia. And today it'll be unique because we'll have Dr. Galveston present in his native language, Spanish, and hopefully it'll allow us to increase our ability to educate across the globe. So at this point, I'm going to turn it over to Dr. Galvis and look forward to his lecture.

Juan Carlos Galvis: Thank you, Dr. Koo. Thank you for having me.

Today I am going to talk to you about radiotherapy guided by Positron emission tomography (PET) prostate-specific membrane antigen (PSMA) in prostate cancer. Basically, PET-PSMA has shown a higher sensitivity than conventional methods. A stable sensitivity and higher specificity.  But we are still defining its role in guiding radiotherapy treatment plans.  At my workplace, we conducted a retrospective observational study with prostate cancer patients in which we made conventional images and we made PET-PSMAs with gallium and 18F.  And we wanted to see to what extent it changed our decision-making in the radiotherapy treatment plan.

Basically, we evaluated the radiotherapy treatment plans if we made them with conventional images, and [SiC – or] if we made them with PET.  Then we evaluated making the plans both ways.  As important features, we saw that patients with high [levels of] glysol presented with metastatic, lymph node or  bone disease. Versus patients with biochemical relapse, more than anything they had lymph node relapses. The traditional volumes that are to be delineated are based on the Radiation Therapy Oncology Group (RTOG) and the other volumes are delineated with the PET.  We found that 89% of patients had positive findings in PET, and only 17% in conventional images. Which results in PET radiotherapy detecting 75% more than the conventional images and that's something we already knew. But the interesting thing is that we saw where the patients relapsed, with this PET.

And the interesting thing is that we saw a lot of changes outside of the traditional fields that we have. Then we saw that most of the lymph nodes were para-aortic and pararectal. and outside of the traditional fields that we do in radiotherapy. That's why the presentation is called: PET-guided radiotherapy. Because PET guides our treatment.  So, PET-PSMA made an improvement in the detection of 77% of patients who were given curative radiotherapy and 69% of those given salvage therapy. And PET changed the treatment plan in 69.2% of patients treated with exclusive radiotherapy and 30% in salvage radiotherapy. Why does the treatment change us? Because we are changing the site where we are directing radiotherapy and it changes the dose that we have to give. This has resulted in radiotherapy using PET as a guide and can be termed as a bio-marker, because it impacts us and guides us with regard to the dose and the fields of radiation. Thank you very much.

Phillip Koo: Thank you, Dr. Galvis. I wish my Spanish was a little better so I could understand all of it, but I was able to get bits and pieces. So I'll ask my questions in English, and feel free to respond in Spanish, but just tell us a little bit about how long you've been using PSMA in your radiation oncology practice and what impact you've seen in your patients. How often are you changing management and whatnot? Because clearly a lot of the data that has been published so far shows a pretty significant change in how we manage patients.

Juan Carlos Galvis: So... Yes. Colombia has been one of the countries pioneering the use of PET-PSMA.  We have been using it more or less since 2016. And it has been readily...It has been very readily received by users and insurers. And the second question… It changed us…The treatment plan changed us by 69%...It changed the plans, the fields of treatment because the lymph nodes were not included in the traditional fields that we have. And moreover, it also changed the dose we have to give because all the points that were marked to us in the PET must have a reinforcement. So there was a significant change.  More than all 77% more or less, in patients undergoing radical cure radiotherapy. And more or less in 50% in patients who had biochemical relapse. It changed the treatment plan for us.

Phillip Koo: So can you also talk a little bit about dose in treatment fields now that you're incorporating PSMA more into your practice?

Juan Carlos Galvis: Yes Traditional fields of treatment more or less in 40% [of the cases] lymph nodes are not included that we are currently seeing in PET.  So we're looking at para-aortic and perirectal lymph nodes that we did not have [before]; the traditional fields did not cover them. And also, in all patients, as I told you before.  All of our patients who have a positive PET, we give a reinforcement or "boost" to the lymph node or to what it marked as positive. So yes it's changing us both in the fields and in the dose.

Phillip Koo: So then, last question is if you looked into the future, now that we have PSMA being used much more widely across the globe, and obviously it's been used in Colombia much longer, where do you think we're going to be heading with regards to radiation oncology and radiotherapy in these patients with prostate cancer?

Juan Carlos Galvis: Well, it has been a very significant change for us because radiotherapy was being performed blind, so to speak, and now we can see exactly what we are irradiating. The point is whether this changes overall survival.  It is one of the points of dispute; however, I believe that in the future the studies are going to show positive results in the use of this better tool to direct radiation therapy. It will impact overall survival.

Phillip Koo:  Great. Thank you very much, Dr. Galvis, for sharing your time and expertise about this exciting topic. I also want to thank all the Spanish-speaking listeners out there who invested the time to listen and learn more about this topic. And this is something new that we're trying, so if anyone has any comments or ways that we can improve on this, please let us know. And we'd love to hear some feedback. So thank you very much, Dr. Galvis.

Juan Carlos Galvis: Thank you very much.