In this episode of ASCO Educational podcasts, we'll explore how we interpret and integrate recently reported clinical research into practice. Part One involved a 72-year old man with high-risk, localized prostate cancer progressing to hormone-sensitive metastatic disease. Today's scenario focuses on de novo metastatic prostate cancer.

Our guests are Dr. Kriti Mittal (UMass Chan Medical School) and Dr. Jorge Garcia (Case Western Reserve University School of Medicine). Together they present the patient scenario (1:13), going beyond the one-size-fits-all approach (4:54), and thinking about the patient as a whole (13:39).

Speaker Disclosures Dr. Kriti Mittal: Honoraria – IntrinsiQ; Targeted Oncology; Medpage; Aptitude Health; Cardinal Health Consulting or Advisory Role – Bayer; Aveo; Dendreon; Myovant; Fletcher; Curio Science; AVEO; Janssen; Dedham Group Research Funding - Pfizer

Dr. Jorge Garcia: Honoraria - MJH Associates: Aptitude Health; Janssen Consulting or Advisor – Eisai; Targeted Oncology Research Funding – Merck; Pfizer; Orion Pharma GmbH; Janssen Oncology; Genentech/Roche; Lilly Other Relationship - FDA

Resources ASCO Article: Implementation of Germline Testing for Prostate Cancer: Philadelphia Prostate Cancer Consensus Conference 2019 ASCO Course: How Do I Integrate Metastasis-directed Therapy in Patients with Oligometastatic Prostate Cancer? (Free to Full and Allied ASCO Members) If you liked this episode, please follow the show. To explore other educational content, including courses, visit education.asco.org. Contact us at education@asco.org.

TRANSCRIPT

Disclosures for this podcast are listed on the podcast page.

Dr. Kriti Mittal: Hello and welcome to this episode of the ASCO Education Podcast. Today, we'll explore how we interpret and integrate recently reported clinical research into practice. In a previous episode, we explored the clinical scenario of localized prostate cancer progressing to metastatic hormone-sensitive disease. Today, our focus will be on de novo metastatic prostate cancer. My name is Kriti Mittal and I am the Medical Director of GU Oncology at the University of Massachusetts. I am delighted to co-host today's discussion with my colleague, Dr. Jorge Garcia.

Dr. Garcia is a Professor of Medicine and Urology at Case Western Reserve University School of Medicine. He is also the George and Edith Richmond Distinguished Scientist Chair and the current Chair of the Solid Tumor Oncology Division at University Hospitals Seidman Cancer Center.

Here are the details of the patient case we will be exploring: The patient also notes intermittent difficulty in emptying his bladder with poor stream for the last six months. A CT scan of the abdomen and pelvis demonstrates enlarged prostate gland with bladder distension, pathologically enlarged internal and external iliac lymph nodes, and multiple osteolytic lesions in the lumbar sacral, spine, and pelvic bones. A CT chest also reveals supraclavicular lymphadenopathy and sclerotic foci in three ribs. So this patient meets the criteria for high-volume disease and also has axial and appendicular lesions.

The patient was admitted for further evaluation. A bone scan confirmed uptake in multiple areas identified on the CT, and a PSA was found to be greater than 1500. Biopsy of a pelvic lymph node confirmed the diagnosis of prostate cancer. This patient is somewhat different from the first case we presented in terms of timing of presentation; this patient presents with de novo metastatic high-volume disease, in contrast to the first patient who then became metastatic after undergoing treatment for high-risk localized disease.

Would you consider these two cases different for the purposes of dosing docetaxel therapy when you offer upfront triplet therapy combinations?

Dr. Jorge Garcia: That's a great question. I actually do not. The natural history of someone with localized disease receiving local definitive therapy progressing over time is different than someone walking in with de novo metastatic disease. But now, with the challenges that we have seen with prostate cancer screening, maybe even COVID, to be honest with you, in North America, with the late care and access to testing, we do see quite a bit of patients actually walking in the office with de novo metastatic disease. So, to me, what defines the need for this patient to get chemotherapy is the volume of his disease, the symptoms of his disease – to be honest with you – and the fact that, number one, he is clinically impaired. He has symptomatic disease, and he does have a fair amount of disease, even though he may not have visceral metastasis. Then his diseases give him significant pain.

Oral agents are very good for pain control. I'm not disputing the fact that that is something that actually these agents can do. But I also believe I'm senior enough and old enough to remember that chemotherapy, when it works, can actually really alleviate pain quite drastically. So for me, I think that the way that I would probably counsel this patient is to say, "Listen, we can give you ADT plus an oral agent, but I really believe your symptomatic progression really talks about the importance of rapid control of your disease." And based upon the charted data from the United States, and equally important, PEACE-1, which is the French version of ADT, followed by abiraterone, if you will, and certainly ARASENS is the standard of care for me for a patient like this will be triple therapy with ADT and docetaxel.

What I think is important for us to remember is that, in ARASENS, it was triple therapy together. I am worried sometimes about the fatigue that patients can have during the first six cycles of docetaxel. So oftentimes, I tell them if they're super fit, I may just do triple therapy up front, but if they I think they're going to struggle, what I tell them is, "Hey, we're going to put you on ADT chemotherapy. Right after you're about to complete chemo, we'll actually add on the darolutamide." So I do it in a sequence, and I think that's part of the data; we just still don't know if it should be given three at front or ADT chemo, followed by immediately, followed by an ARI. So I love to hear if that's how you practice or you perhaps have a different thought process.

Dr. Kriti Mittal: So I usually start the process of prior authorization for darolutamide the day I meet them for the first time. I think getting access to giving docetaxel at the infusion center is usually much faster than the few weeks it takes for the prior authorization team to get copay assistance for darolutamide. So, in general, most of my patients start that darolutamide either with cycle two or, depending on their frailty, I do tend to start a few cycles in like you suggested. I've had a few patients that I've used the layered-in approach, completing six cycles of chemotherapy first and then layering in with darolutamide.

I think conceptually the role of intensifying treatment with an androgen receptor inhibitor is not just to get a response. We know ADT will get us a PSA response. I think the role of an androgen receptor inhibitor is to prevent the development of resistance. So, delaying the development of resistance will be pertinent to whether we started with cycle one, cycle six, or after. So, we really have to make decisions looking at the patient in front of us, looking at their ECOG performance status, their comorbidities, and frailty, and we cannot use a one-size-fits-all approach.

Dr. Jorge Garcia: Yeah, I like that and I concur with that. Thank you for that discussion. I think that you may recall some of our discussions in different venues. When I counsel patients, I tell the patients that really the goal of their care is on the concept of the three Ps, P as in Peter. The first P is we want to prolong your life. That's the hallmark of this regimen, the hallmark of the data that we have. That's the goal, the primary goal of these three indications is survival improvement. So we want to prolong your life so you don't die anytime soon from prostate cancer.

The second P, as in Peter, is to prevent, and the question is preventing what? We want to prevent your cancer from growing, from growing clinically, from growing radiographically, and from growing serologically, which is PSA and blood work. Now, you and I know and the audience probably realize that the natural history of prostate cancer is such that traditionally your PSA will rise first. There is a lead time bias between the rise and the scan changes and another gap in time between scans and symptoms. So it's often not the case when we see symptomatic disease preceding scans or PSAs, but sometimes in this case, it's at the same time. So that is the number one. And as you indicated, it's prevention of resistance as well, which obviously we can delay rPFS, which is a composite endpoint of radiographic progression, symptomatic progression, and death of any cause.

But the third P is I called it the P and M, which is protecting and maintaining, and that is we want to protect your quality of life while we treat you. And we want to maintain your quality of life while we treat you. So to me, it's critically important that in addition of aiming for an efficacy endpoint, we don't lose sight of the importance of quality of life and the protection of that patient in front of us. Because, undoubtedly, where you get chemo or where you get an oral agent, anything that we offer our patients has the potential of causing harm. And I think it is a balance between that benefit and side effect profile that is so critically important for us to elucidate and review with the patient.

And as you know, with the charted data, Dr. Alicia Morgans now at Dana-Farber, published a very elegant paper in JCO looking at the impact of docetaxel-based chemotherapy as part of the charted data in the North American trial and into quality of life. And we clearly define that your quality of life may go down a bit in the first few months of therapy, predictably because you're getting chemotherapy. But at the end of the six months, nine months, and certainly at the end of a year mark, the quality of life data for those who receive ADT and chemotherapy was far better than those who actually got ADT alone.

Now, if you look at the quality of data for RSNs, a similar pattern will appear that although chemotherapy is tied to misconceptions of significant toxicity, in our hands, in good hands, and I think our community of oncology in North America are pretty familiar with the side effects and how to manage and minimize side effects on chemotherapy, I think it still requires a balance and a thoughtful discussion to make sure that we're not moving forward chasing a PSA reduction at the expense of the quality of life of the patient. So I think orchestrating that together with the patient as a team is critically important as well.

Dr. Kriti Mittal: Thank you, Dr. Garcia. Moving on to the next concept we'd like to discuss in today's podcast the role of PARP inhibitors. Case Two was treated with androgen deprivation docetaxel and darolutamide. Consistent with current guidelines, the patient was also referred to germline testing and was found to be BRCA 2-positive. The patient's disease remained stable for 24 months, at which time he demonstrated disease progression, radiographically and clinically, and his disease was termed castration-resistant. There has been a lot published in the last few years regarding the role of PARP inhibitors in metastatic castration-resistant prostate cancer, or mCRPC.

The PROfound trial led to the approval of olaparib in patients with deleterious mutations in HRR genes for those who had been treated previously with AR-directed therapy. The TRITON2 trial led to the approval of rucaparib in the same month for mCRPC patients with BRCA mutation for those patients who had previously been treated with AR inhibitors and taxine-based chemotherapy. More recently, we saw data from the TRITON3 trial exploring the role of rucaparib versus physicians' choice of docetaxel versus AR-inhibitor therapy in the mCRPC space for patients harboring BRCA 1, BRCA 2, or ATM mutation. Based on these data, it would be very tempting to offer a PARP inhibitor to the patient in case two. While regulatory authorities are still reviewing those data for approval, how would you consider treating this newly castrate-resistant patient in the frontline setting? Would you consider a PARP inhibitor in the frontline treatment of mCRPC in this patient with a BRCA 2 mutation?

Dr. Jorge Garcia: So that's a loaded question, to be honest with you. We have compelling data, but controversial data, as you know as well. So I think that since we have a genomic profile on this patient and we know he had high volume disease, then the first thought to me is not a genetic or a genomic question or a sequence. It's actually a clinical question, to be honest with you. And that is: How are you progressing? Because I think that if you're progressing serologically, you and I may think of that patient differently. If you're progressing radiographically with alone plus minus PSA production but no symptoms, you may also tilt your scale into this life-prolonging agents in a different way. Whereas if you have true symptomatic disease, knowing what you know, prior therapy, CrPC with a BRCA 2 alteration, then you may actually go for something different.

So if it's a rising PSA, if it is radiographic, but the patient is stable clinically, is not basically compromised by symptomatic disease, I do feel that a PARP inhibitor as a single agent would be a very reasonable choice. In this case, you can use, obviously, rucaparib. You can use olaparib. I don't have a vested interest in either/or. I think either/or is fine. The subtleties and side effects, as you know, the olaparib data was probably the data that you and I probably are more accustomed to, used to the most just by virtue of how the agents got registered in the United States. But either/or, I think a PARP inhibitor would be a reasonable approach.

I think the question perhaps, and I pitch that back to you, is what are you looking for with a PARP inhibitor? Because, as you know, all DNA repair deficiencies are not biologically the same. They do not respond the same way to PARP inhibitors. And even BRCA 2, where we think it's monoallelic or biallelic, may have subtleties in how those patients respond to PARP therapy. But the answer is yes, obviously, you have a biomarker, the patient has it, you can use it. I think the question is, how are you going to follow the patient? And what is going to be the endpoint that you're going to pay attention to in this case to find that the patient has a benefit or not granted, that could be PSA driven, but I think that perhaps I'm pushing you to think beyond PSA.

Dr. Kriti Mittal: I agree, Dr. Garcia. I think we need to think about the patient as a whole. PSA-based changes in treatment are not generally part of our practice. I think evaluating the patient for symptoms and also thinking about the sites of progression, sites of disease they've had in the past, preventing development of cord compression, because some of these patients progress very rapidly and present with cord compression at the time of progression. Those are the things we are trying to predict and prevent. I think in a patient with BRCA 2 mutation, in this situation, I would feel compelled to offer rucaparib, given that even in the intention-to-treat analysis, the hazard ratio was 0.6 in terms of median progression-free survival. I think what was quite impressive was the subset analysis comparing rucaparib versus docetaxel. And that was something surprising. And I think we'll have to wait for long-term outcomes. But certainly, for a BRACA 2-mutated patient, this could be a reasonable consideration provided the drug is available and approved.

Dr. Jorge Garcia: As you know, the three most common DNA repair deficiencies that we see are BRCA1, BRCA2, and ATM. BRCA2 is probably the one that we see the most. But we also recognize that with the limited data we have for ATMs, that patients with an ATM abnormality do not tend to benefit the most. And then yet we have also another series of DNA repair deficiencies, deficiencies, PALB2, CHEK2, CDK12 and so forth. And yet we have some exquisite responses to some of those patients.

So I can tell you that I have a patient of mine who had an ATM mutation, a germline ATM mutation, and I predicted that initially that the likelihood of benefit to a PARP inhibitor would be low. He was placed on a PARP inhibitor and surprise, surprise, he was on a PARP inhibitor for almost a couple of years. What I want to convey to the audience is that if you have the appropriate biomarker, you certainly should consider a PARP inhibitor in this scenario.

I think the bigger question is also understanding that not every DNA repair would benefit the same way. So being very thoughtful and very structured as to how you're going to manage the patient, it cannot be PSA only, the patient has to be followed radiographically and clinically because I would argue that if this patient had just a serologic progression, I would put the patient on a PARP inhibitor and the PSA kinetics change north, but slowly, what is the urgency of you switching the patient to something else?

And also the misconception that if you look at PROfound, that olaparib for that matter has to always be given after docetaxel. That's not the case. The makeup of PROfound is different than this patient, obviously, because this patient got triple therapy upfront, whereas most patients on the PROfound were CRPC who receive chemotherapy in the CRPC space. But yet undoubtedly, I think that your case illustrates the importance of next-generation sequencing and the importance of understanding the access to two oral PARP inhibitors that are super solid.

I think that perhaps the bigger question is going to be should you do a PARP inhibitor alone or should we use a combination of a PARP inhibitor plus an oral agent, such as in this case, maybe abiraterone acetate plus olaparib. Or maybe even thinking of TALAPRO, maybe enza plus a PARP inhibitor. So I don't know where you sit on those thoughts, Doctor-.

Dr. Kriti Mittal: I change toxicity considerations, temper my enthusiasm for offering PARP inhibitors in combination with AR inhibitors or abiraterone at this time. I think I would certainly consider monotherapy with rucaparib for a patient in this situation. I am not entirely convinced that putting a patient through dual treatment in the mCRPC setting in the frontline, I don't think we are there yet.

Dr. Jorge Garcia: There are two very important trials that are looking at the combination of an adrenal biosynthesis inhibitor plus olaparib in this context, and one is PROpel and the other one is MAGNITUDE. And both trials have very different results in many ways because they look at patients with a biomarker, meaning DNA repair, and patients without the biomarker. And I think the bigger question is, should this patient who was an abiraterone– Let's say this patient hypothetically was on a PEACE-1-like style. So the patient got ADT or triple therapy but was an abiraterone or an adrenal biosynthesis inhibitor instead of chemotherapy. And the patient was progressing slowly on abiraterone, you knew that the patient had a DNA repair deficiency. How comfortable with the PROpel and MAGNITUDE data would you and I feel to add on or layer, if you allow me to express it like that, a PARP inhibitor into this regime?

Dr. Kriti Mittal: My personal interpretation of the currently available data is that at this point, combination therapy is not something I would use in my clinical practice. I think there are two camps in the GU oncology community of how people interpret the PROpel, MAGNITUDE, TRITON, and TALAPRO data in full. I think each of these trials had very different patient populations. I think in a biomarker unselected population, I would certainly not advocate for combination therapy. But even in the biomarker-selected population, I think how the biomarkers were tested and how the populations were defined may not always match what we are doing in clinical practice. And so I would, at this time, advocate for monotherapy over combination therapy.

Dr. Jorge Garcia: I'm sure the audience will have probably read or heard about PROpel and MAGNITUDE and the data in patients without a biomarker positivity disease. So I'd love to hear your thoughts as to if you had no biomarker. By that I mean if you had a patient with CRPC, with metastatic CRPC without a DNA repair deficiency, would you consider using an adrenal biosynthesis inhibitor and a PARP inhibitor together based upon the potential synergistic of additive benefits and some of the data to suggest that you can delay rPFS when you combine therapy, but in the absence of biomarker positivity.

Dr. Kriti Mittal: In the absence of biomarker positivity, I think the preclinical data are stronger than the clinical results we are seeing in trials. So while I think we should continue researching further into this because there certainly is preclinical rationale, looking at the clinical outcomes from these several trials, I would not offer PARP inhibitor to an unselected patient.

Dr. Jorge Garcia: Great.

Dr. Kriti Mittal: Moving on to second-line treatment for castration-resistant prostate cancer. I think talking of access issues and talking about the current treatment paradigms in the United States, there is still not widespread availability of lutetium. The listeners would love to hear your thoughts, Dr. Garcia, on practical management tips, safety issues, and the multidisciplinary nature of the management of lutetium therapy.

Dr. Kriti Mittal: So I think the challenges with lutetium are multiple. Number one is the correct identification of the patient, the ideal patient for lutetium. Secondly is who manages the patient and as you indicated, the importance of a team approach in that. Thirdly is how do we follow that patient during therapy? So it's beyond the technical aspects of who infuses the patient. Fourthly is what are the true goals of lutetium for that patient population and the side effects that those patients may embark on that some people may not be fully aware of and creates complexity. And lastly, perhaps, is how the movement, how we develop lutetium in CRPC and how we're going to move lutetium or have started to move lutetium and alike, meaning radiopharmaceuticals, radioligand-based therapies outside lutetium opinion and others as you know, earlier into the natural history of prostate cancer, maybe even in the locally advanced disease in combination with radiation or for patients with N1 positive disease. So it's a lot of movement in that space. I think that this is just the beginning of radiopharmaceutical entering diagnostics.

But let me just address this succinctly, if I may. Number one, you do need a PET PSMA in order for you to select the patient because we're talking about a potential biomarker. But this is what I call an imaging biomarker. If you see it, you treat it. So the standard of care right now for lutetium is very simple: you need to have men with metastatic castration-resistant prostate cancer. Two, you need to have failed a prior oral agent, in this case, a novel hormonal agent, independent of which agent you have seen, independent of the timing when you have seen an oral agent at the front, the middle, the end. And lastly, you have to have progress through chemotherapy. Yet again, it depends on when you see chemo.

So if you have someone who has high volume metastatic disease from the beginning, de novo disease, and you got ADT, daro, and docetaxel, and the patient progresses, that patient can go on. If that patient has a positive PSMA PET, that patient can go on to get lutetium. Similarly, if you have someone who got ADT alone in the adjuvant space for radiation therapy, progress, got an oral agent, progress, got a PARP or not, or got docetaxel, that patient could also be a candidate for lutetium. It's dependent on how you run the patient through therapy.

Secondly is who gives lutetium? So I do believe, and I may be biased, I certainly believe in the importance of a team approach with radiation oncology and nuclear medicine. But the reality of it is, I believe these patients are so advanced in their stage of their disease, then the idea of quarterback, in my personal opinion, resides in medical oncology. And I think the bigger question is going to be if nuclear medicine at your given institution is going to be delivering lutetium, or is it going to be radiation oncology? And I think, as you know, in places in America, it's RadOnC, in other places is NucMed, in our institution right now it is NucMed. Having said that, I do predict that for those places where nuclear medicine is heavily involved in delivering lutetium or partnering with MedOnc to deliver lutetium, radiation oncology in the future will have a bigger role as well because we are moving lutetium earlier in settings where radiation oncology is commonly used, such as high-risk prostate cancer patients, or even in the salvage setting, or even in patients with metastatic disease, where we want to combine radiation and lutetium, which are part of clinical trials as we think through for the future. But either/or, I think the quarterback should be really MedOnc in this case.

Thirdly is how do we do it? So clearly, at least in my practice, and I think it's probably standard across the United States, MedOnc will see the patient, determine viability and feasibility of therapy, determine who's the ideal candidate, discusses the pros and the cons, and then works along with RadOnc or NucMed to start the process. As you know, it is once every six weeks. So here in my practice, we will see the patient every time before treatment. Sometimes we see them the day off, sometimes we see them a few days before. Patients will get blood work. Specifically, we're interested in seeing everything CMPs, but certainly blood counts, red cell counts, platelets, and white cell counts, just to make sure that patients do not start with impaired bone marrow that can increase the risk for myelosuppression and therefore significant challenges with side effects, hematologic side effects, specifically. And we do that.

Sometimes we see them, sometimes our nurse practitioners would do so. And then the patient will basically follow through and complete up to six cycles of treatments. Six times six, that's actually 36 weeks or so. That's a long time on therapy for those who can get six cycles. I think the question becomes how do you follow those patients? And if we pay attention to the VISION data, as you know, those patients were actually followed serially quite closely on trial every eight weeks for the first 24 weeks, and then they stretch the scans out. But the scans that we're using in the trial are conventional imaging.

And I think the bigger question that you and I will have is if we get a PET PSMA to use to make that decision to get on lutetium PSMA, should I go back and use a CT or so to stage the patient? I think we're moving more toward PET follow-up, but we also don't know fully the impact of lutetium PSMA on PSMA metabolically during treatment. I think that we all recognize anecdotally and at least with some of the emerging data and we have the SUV may change, that PSA reductions also appear to be important as to define who is likely to benefit or not. But those are questions that remain to be seen, to be honest with you. We follow the patients serologically, clinically, and radiographically. And at least in my group, we tend to do PSMA PETs in between therapy to ascertain the impact of therapy in radiographic and also metabolic changes.

And lastly is how we manage side effects. So I think that I'm pretty OCD about these patients because I have seen in my practice patients having outstanding responses to therapy but unfortunately become transfusion dependent, either transiently or permanently, just by virtue of side effects. And I think the importance of understanding the most common side effects of lutetium, in this case fatigue, myelosuppression, xerostomia, are really, really important. And that is the importance of having a multi-team effort approach so everybody is fully aware of the baseline characteristics of that patient or how the patient is enduring therapy and how the therapy is impacting the quality of life and impacting bone marrow production for those patients.

I think I remind the audience that the vast majority of our patients do have bone metastases. In fact, in the VISION trial it was around what, over 85, 90% of patients are so with bone metastases. So their marrow has already been impacted not only by disease but equally importantly by the prior chemotherapy that they may have seen. And some of the patients that we have in the first bubble effect is they have seen probably docetaxel, some may even have seen dual therapy with cabazitaxel as a second-line chemotherapy. So I think the understanding as to how you manage the side effects is critically important for our patients as well.

Dr. Kriti Mittal: Those are very relevant, practical life issues. Thank you Dr. Garcia for a terrific discussion on the application of recent advances in prostate cancer to clinical practice. [28:54] The ASCO Education podcast is where we explore topics ranging from implementing new cancer treatments and improving patient care to oncologists' well-being and professional development. If you have an idea for a topic or a guest you'd like to see on the ASCO Education Podcast, please email us at education@asco.org. To stay up to date with the latest episodes and explore other educational content, please visit education.asco.org.

Dr. Jorge Garcia: Thank you, Kriti. It's great to see you and thanks again to ASCO for the amazing opportunity to be here with you guys today. I hope the audience can see the benefit of understanding how the many changes we have seen have impacted our patients in a positive way. So thank you again for the opportunity.

Dr. Kriti Mittal: Thank you, Dr. Garcia, and thank you so much to the ASCO team for inviting me. This was a great experience.

Thank you Dr. Garcia for sharing your perspective on incorporating recent research advances into the management of patients with de novo metastatic prostate cancer.

The ASCO Education Podcast is where we explore topics ranging from implementing new cancer treatments and improving patient care to oncologists' well-being and professional development. If you have an idea for a topic or a guest you'd like to see on the ASCO Education Podcast, please email us at education@asco.org. To stay up to date with the latest episodes and explore other educational content, please visit education.asco.org.

The purpose of this podcast is to educate and to inform. This is not a substitute for professional medical care and is not intended for use in the diagnosis or treatment of individual conditions.

Guests on this podcast express their own opinions, experiences, and conclusions. Guest statements on the podcast do not express the opinions of ASCO. The mention of any product, service, organization, activity, or therapy should not be construed as an ASCO endorsement.

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