Germline and Somatic Genomic Testing for Metastatic Prostate Cancer Guideline

Dr. Evan Yu presents the new evidence-based guideline on genetic testing for metastatic prostate cancer. He discusses who should receive germline and somatic testing with next-generation sequencing technologies, what samples are preferred for testing, and the therapeutic & prognosistc impacts of genetic testing. Dr. Yu emphasizes the need for awareness and refers to areas of active investigation and future research to improve personalized therapies for patients with metastatic prostate cancer.

Read the full guideline, "Germline and Somatic Genomic Testing for Metastatic Prostate Cancer: ASCO Guideline" at www.asco.org/genitourinary-cancer-guidelines.

TRANSCRIPT

This guideline, clinical tools, and resources are available at http://www.asco.org/genitourinary-cancer-guidelines. Read the full text of the guideline and review authors' disclosures of potential conflicts of interest in the Journal of Clinical Oncology, https://ascopubs.org/doi/10.1200/JCO-24-02608

Brittany Harvey: Hello and welcome to the ASCO Guidelines podcast, one of ASCO's podcasts delivering timely information to keep you up to date on the latest changes, challenges and advances in oncology. You can find all the shows, including this one at asco.org/podcasts.

My name is Brittany Harvey and today I'm interviewing Dr. Evan Yu from the University of Washington and Fred Hutchinson Cancer Center, lead author on "Germline and Somatic Genomic Testing for Metastatic Prostate Cancer: ASCO Guideline". Thank you for being here today, Dr. Yu.

Dr. Evan Yu: Thanks for having me on.

Brittany Harvey: Great. Then before we discuss this guideline, I'd like to note that ASCO takes great care in the development of its guidelines and ensuring that the ASCO Conflict of Interest policy is followed for each guideline. The disclosures of potential conflicts of interest for the entire guideline, including Dr. Yu, who has joined us here today, are available online with the publication of the guideline in the Journal of Clinical Oncology, which is linked in the show notes.

So then, Dr. Yu, to start us off on the content of this guideline, could you first provide an overview of both the purpose and scope of this guideline?

Dr. Evan Yu: Yeah, absolutely. So I think the one key thing to recognize is that prostate cancer is the highest incidence of all cancers in males. Additionally, it's the second highest cause of mortality in males, and that's about 35,000 deaths in 2024. So with that being said and done, it's a disease where we need to do better. And part of that is recognizing that we now have many targeted therapies, precision medicine type of therapies, but unlike a lot of other cancers out there, prostate cancer patients are not always getting sequencing, next generation DNA sequencing, let's say, to identify both inherited and also spontaneously develop what we call somatic mutations in their tumor. And I suspect that's partially because other cancers like breast cancer, we're so used to- in the first line, you present the patient, you throw out their estrogen receptor status, progesterone receptor status, HER2, ER/PR HER2; in lung cancer it's EGFR, ALK, ROS1, etc. In things like prostate cancer, things like BRCA2 have major important patient treatment implications and potentially family counseling and downstream cascade testing implications. But it hasn't made their way into that first-line presentation yet. And for that reason, there are some studies out there that show that testing in the community may be as low as 15% of patients with metastatic prostate cancer. We want to bring awareness to that and hopefully increase testing down the road so that we can better help our patients with metastatic prostate cancer.

Brittany Harvey: Absolutely. It's important to get these targeted therapies to the patients who can benefit most. Using that context, I'd like to next review the key recommendations of this guideline across the six clinical questions that the panel addressed. So, starting with: Who should receive germline testing with next generation sequencing technologies?

Dr. Evan Yu: Yeah. We think that it's common enough that everyone with metastatic prostate cancer should receive germline genetic testing. And the reason for that is there have been studies that have looked at this and have shown that 12% of men with metastatic prostate cancer have some sort of inherited germline mutation in a gene, mostly DNA repair genes. But 12% have something that is inherited and that loved ones, first degree relatives, siblings, offspring might have also inherited. Now, most of these are in the DNA repair genes, but that being said and done, there's not only treatment implications for the patient, where there are newer drugs that that patient could get treated with, but other loved ones that might have inherited these gene mutations, that these things can cause other cancers as well - not just prostate cancer, but breast cancer, endometrial cancer, ovarian cancer, pancreatic cancer. So, it's very important to test, with as high of an incidence as 12%, to test, and if you identify it in a patient, it's our job to talk to the patient about it and talk to them about the pros and cons of family counseling and talking to their loved ones and potentially having their loved ones get tested. Because if they test positive, then their doctors may want to know and may screen them very, very aggressively and differently for a whole host of other cancers. And the whole idea is you find the cancer very early and cure the patients before the cancer really takes hold and has the ability to spread so we can save a lot of lives down the road.

Brittany Harvey: Absolutely. This germline testing is important not just for the patient, but has wider implications for their families as well, as you mentioned.

So then, beyond those recommendations for germline testing, which patients should receive somatic testing with next-generation sequencing technologies?

Dr. Evan Yu: So let's talk a little bit about somatic testing. So germline again, as we know, is inherited. The patient inherited it in every single cell in their body, then it becomes very easy, many of these are cancer predispositions for them to lose the other allele and then to have biallelic loss and then develop the cancer. Now, somatic just means it spontaneously occurred. Certainly, it's not going to occur in every cell in the body, but you can get one hit, lose one allele and then lose the other allele. And if that gene is truly carcinogenic and leading to that cancer, then that can have implications potentially for treatment as well. So we recommend that all patients with metastatic prostate cancer also undergo somatic next-generation sequencing testing. We recognize that at this point in time it's only those with metastatic castration-resistant prostate cancer or hormone-resistant prostate cancer, which is a later disease state where there are drugs that may target those mutations, for instance, like PARP inhibitors, but that early identification for a patient population that's fit and that can benefit from these therapies makes sense so that you know it's in place already and you have your treatments outlined and mapped out for the future. So we recommend it for everybody - somatic testing also for everyone with metastatic prostate cancer.

Brittany Harvey: Understood. And then when patients are receiving that somatic testing, what is recommended for somatic testing? Primary tumor archival tissue? Fresh metastatic biopsy tissue? Or circulating tumor DNA testing?

Dr. Evan Yu: We recommend that in the initial setting when you're first diagnosed, that archival tissue samples are fine and preferred. But circulating tumor DNA is good when there's no accessible archival tissue, or if the archival tissue, let's say, is very old and it's been sitting around for a long time, or you can't get it anymore because it's many years back when maybe a patient had a prostate needle biopsy. So if it's not accessible, then we recommend ctDNA. We believe that is preferred and also that ctDNA is recommended in a situation where you can't easily biopsy a metastatic site. Sometimes it's just not in a safe area to go after. Sometimes it's just a small lesion. So in general, we recommend tissue when available, and when we think that the tissue sample will yield clean results, if not, then we recommend doing ctDNA at that point in time.

Brittany Harvey: So you have described who should get germline and somatic genomic testing. But what are the therapeutic impacts of this germline or somatic testing for single gene genetic variants?

Dr. Evan Yu: We pulled this panel together and we met like every single month for like 12 months straight, and part of it was to review the literature. And as part of this literature review, we were able to pull a whole bunch of different trials. I think there was like 1713 papers we identified in the literature search. Eventually, we narrowed it down because with ASCO, we want to present the data with the highest level evidence, level 1 evidence, randomized controlled prospective data. And after reviewing 1713 papers, we narrowed it down to 14 papers. With those 14 papers, if you look at it, there are a lot of things that we think may have implications for treatment or prognosis, but we didn't feel was the highest level of evidence that we could support. So the things that have the highest level of evidence that we can support are certain DNA repair gene alterations, especially BRCA2, and treatment with PARP inhibitors because there are many PARP inhibitor prospective trials that show progression-free survival benefit and even overall survival benefit. And so that's the type of study that achieved the level of evidence that we could include. So I would say BRCA1 and BRCA2 highest level of evidence and PARP inhibitor use also is included in that.

Brittany Harvey: Understood. I appreciate you reviewing those therapeutic options. So then, the last clinical question, which you just touched on briefly, but what are the prognostic impacts of germline and/or somatic testing?

Dr. Evan Yu: Whenever you do testing, especially if you use panel testing, you find a lot of information. There's a lot of different mutations and some of which are VUSs (variants of unknown significance) where we don't quite know what it means yet, but we can track that, especially if it's germline. But with somatic, we find lots of things that have implications, but maybe just not treatment implications. A perfect example is p53. p53 is one of the most common tumor suppressor gene mutations on all cancers, but in prostate cancer they can occur and they can usually occur late, although there can even be germline inherited p53 alterations. There's no treatment that targets p53 right now, but we know that if you have a p53 mutation that those patients may have more aggressive disease and that prognostic information is important to give to the patient. And I think it's important for future clinical trial design and direction. So we do not recommend making treatment recommendations or changes based on these prognostic only biomarkers at this point in time. But we do recommend that, based on this, we can design intensification trials for those patients who have these poor risk biomarkers and de-intensification trials for patients who may have a good risk biomarker. So for instance, SPOP is a gene where we think these patients may have better outcomes, they might respond better to certain hormonal therapies like abiraterone. I say might because the level of evidence isn't quite there. But what I would say is that these prognostic only biomarkers, we just don't think they cut the mustard yet to be able to make treatment decisions. But we do think that they can drive counseling for the patient and potential selection and trial design for the future to say, "Okay. This is a patient population that has a more aggressive cancer. We need to be more aggressive in treating these patients." "This patient population might have a less aggressive cancer. Maybe we can de-intensify and say side effects and quality of life may be better for the patients."

Brittany Harvey: Definitely. It's important for thinking through how to personalize care for these patients.

So then you've talked about this a little bit in talking through the recommendations, but could you expand on what is the importance of this guideline and how it will impact both clinicians and patients with metastatic prostate cancer?

Dr. Evan Yu: Yeah, I think the number one thing is awareness. I think the data's out there and people that are in my field, they know this. But by evidence of the fact that it's not first-line presentation lingo that everyone's talking about things like BRCA status, it means it hasn't necessarily disseminated all the way through. So it's increasing awareness of the fact that both germline and somatic alterations can occur and that these may have impacts on the patient for their treatment and their prognosis, and basically to increase testing for the future. I really think that in the future, there'll be other reasons that we may want to serially even retest and we may find that there may be mutations that develop as mechanisms of resistance that might guide therapy down the road. So we need to get people to start doing this for everyone with metastatic prostate cancer, because someday we might be doing it not just once, but over and over again.

Brittany Harvey. Absolutely. We hope this guideline reaches a wide audience and that these recommendations can be put into practice.

Finally, you've talked about how not all the data in the field has yet risen to the level of evidence that made it into the guidelines. So what are the outstanding questions in future research areas for both germline and somatic genomic testing for metastatic prostate cancer?

Dr. Evan Yu: It was in our discussion, but it clearly- it's not common enough for there to be randomized prospective trials that would reach that level of evidence to make it in this guideline recommendation. But we all know that for any solid tumor, you can get mismatched repair deficiency, microsatellite instability leading to hypermutation or high tumor mutational burden. And that happens in maybe 3 to 5% of patients with metastatic prostate cancer as well. There is evidence and data that these patients can potentially benefit from immunotherapies like pembrolizumab. But again, it's just not common enough for there to be those randomized prospective controlled trials out there. But we mention it because we know it's FDA-approved across all the tumor types, so we felt like we have to mention it because that's something that has treatment implications for the patient.

But also, I alluded to this earlier, I think an area of active investigation is the tried and true number one driver of prostate cancer, which is androgen receptor. Testosterone binds to androgen receptors, stimulates it. That's how androgen deprivation therapy works. That's how abiraterone and the amides like enzalutamide, apalutamide, darolutamide, that's how they all work. But even beyond that, we're starting to identify that maybe 15%, 20% of patients with metastatic castration resistant prostate cancer have androgen receptor mutations. And there are newer classes of therapies like androgen receptor degraders like CYP11A1 antagonist that lead to complete adrenal annihilation of other steroid hormones that might promiscuously stimulate these androgen receptor mutants. These things develop as mechanisms of resistance, and in the future, we might want to serially test- and that's an active area of investigation in the future, to say you've been treated, let's say, with androgen deprivation therapy and abiraterone for years. There are certain mutations that might develop as a resistance mechanism. We might need to serially test somebody because you didn't have that mutation earlier on, but later in the disease course you might. And then there might be a new drug X out there that we would want to use. Again, we need the data, we need the randomized prospective controlled trials, but they're happening out there. And somewhere down the road we may rewrite this guideline and have a lot more recommendations to add to it.

Brittany Harvey: Yes, we'll look forward to more research in this field to better provide targeted therapies for patients with metastatic prostate cancer across the treatment paradigm. And we'll look forward to report outs from those trials that you mentioned.

So I want to thank you so much for your work to develop this guideline and thank you for your time today, Dr. Yu.

Dr. Evan Yu: Thank you so much. It's wonderful to be here today.

Brittany Harvey: And thank you to all of our listeners for tuning in to the ASCO Guidelines podcast. To read the full guideline, go to www.asco.org/genitourinary-cancer-guidelines. You can also find many of our guidelines and interactive resources in the free ASCO Guidelines app, which is available in the Apple App Store or the Google Play Store. If you have enjoyed what you've heard today, please rate and review the podcast and be sure to subscribe so you never miss an episode.

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