Robin Huiras (00:01):

Hello, and welcome to today's installment of Diagnostics in Practice, where we discuss new and innovative test offerings from Mayo Clinic Laboratories. I'm Robin Huiras, a senior marketing specialist with Mayo Clinic Labs, and today I am joined by two Mayo Clinic experts. Dr. Mrinal Patnaik is a Mayo Clinic hematologist who specializes in caring for patients with blood cancers. And Dr. Gang Zheng is a Mayo Clinic hematopathologist and laboratory testing expert who help develop Mayo Clinic Laboratory's new high sensitivity clonal hematopoiesis assay, which is what we'll be focusing on for our discussion today. Thanks, Dr. Patnaik and Dr. Zheng, for being here.

Dr. Zheng (00:40):

Thank you for having me.

Dr. Patnaik (00:42):

Yeah, glad to be here.

Robin Huiras (00:43):

Now, before we begin, I'm wondering if each of you can provide just a little bit of information about yourselves and your experience at Mayo Clinic, especially as it pertains to clonal hematopoiesis. Dr. Patnaik, let's start with you.

Dr. Patnaik (00:56):

Thank you. So I'm a hematologist physician scientist, and I've been here for close to two decades, really trying to focus on the early detection of blood cancers and interception, which is a much easier stage at which we can treat blood cancers, given how many challenges we face when patients develop overt leukemia, which is the reason why we are here today discussing this test.

Robin Huiras (01:22):

Great. Thanks, Dr. Patnaik. And Dr. Zheng?

Dr. Zheng (01:25):

Yes. So I'm a pathologist specializing in molecular pathology and hematopathology, and I also serve as director for Clinical Genomics Lab at Mayo Clinic. Our work focus is molecular diagnostics in oncology and hematology.

Robin Huiras (01:40):

Thank you both so much for sharing. Your experience and expertise in this testing area really does highlight the skill and acumen that supports test development at Mayo Clinic Labs. Now, to kick off our conversation, I'd like to set the stage for our listeners. Dr. Patnaik, what is clonal hematopoiesis and why should clinicians be paying attention to it?

Dr. Patnaik (02:00):

Yeah, so clonal hematopoiesis, very simplistically, is the acquisition of changes in the DNA code in hematopoietic stem cells. So we are born with a fixed number of stem cells, and they repopulate and make all our blood counts. And we have a massive turnover of these counts that's only possible because of the stem cell reserve. And when some of these stem cells acquire certain mutations or changes in the DNA code based on all the pressures that they have to undergo, these can select out, and over time cause problems in the body — not just cancer. There are several other issues that arise from them, and that is what we define as clonal hematopoiesis.

Robin Huiras (02:45):

Thanks so much for sharing that information. I'm wondering, is it fair to say that not all clonal hematopoiesis carries the same level of risk?

Dr. Patnaik (02:53):

Yeah, that's absolutely correct. I would conservatively estimate in North America that there are approximately 20 to 30 million people who have clonal hematopoiesis. And fortunately, less than 20,000 of these will go on to develop blood cancers or leukemia. So there are certain variants, there are certain situations that are more at risk. A large number of them will not develop blood cancers. And so I think the most important point to understand is it's not just the mutation, but it's also the individual, certain hereditary predispositions that they may be born with. But most importantly, what kind of pressures, or selection pressures, as we like to call it, they're going to be exposed to. So if an individual who's aging for some unfortunate reason is going to need more chemotherapy or radiation for other cancers, or has exposures to similar agents, that influences these clones and makes them more likely to cause problems than others.

So it's not just the mutation; it's the context in which the mutation occurs. And it is the context in which it grows.

Robin Huiras (04:08):

I see. So I understand what you're saying to mean that potentially certain therapies will cause clonal hematopoiesis to form.

Dr. Patnaik (04:16):

Yeah, I don't think they necessarily cause it, but they will allow for them to grow out more potently, much quicker, and more problematically. So if I had to simplify this, in our 50s or 60s, almost 50% of individuals may have small amounts of clonal hematopoiesis mutations in their blood. These are very small, and if those individuals age normally without any significant inflammation or exposures to radiation or chemotherapy, these mutations may not do anything. But you take one of those individuals, and let's say they get breast cancer or prostate cancer and now we're giving them chemo or radiation, those mutations are very dynamic, tend to grow much quicker, and tend to cause a lot of problems.

Robin Huiras (05:05):

Let's talk a little bit more about that. Are there certain treatments or protocols and different patient populations that are most strongly associated with developing therapy-related clonal hematopoiesis?

Dr. Patnaik (05:16):

Yeah, not all therapies are the same, and that's very much true for therapy-related clonal hematopoiesis. In the last decade, we have seen certain circumstances that really potentiated. The first that comes to mind are women with ovarian cancer, many of whom have hereditary mutations that increase their risk for not just ovarian cancer, but cancer in general. When they present with advanced disease after surgery, they usually get a chemotherapeutic agent called carboplatin with paclitaxel, and that carboplatin, we know selects out these mutations. And many times, if they have mutations in the BRCA or BRCA-like genes, which are hereditary genes, they get put on a new medication called a PARP inhibitor, which is exploiting some of these problems they have in DNA repair. So I think that sequence and combination really accentuates clonal hematopoiesis. And when these PARP inhibitors were approved over a decade ago, we started seeing a lot of women present with low blood counts and were eventually diagnosed to have myelodysplastic syndrome, which is a form of leukemia, and those are very aggressive with poor outcomes.

The other area that I have to mention is in the field of radiation there are drugs called as radioisotopes. So these are drugs that emit either alpha or beta particles, which are forms of radiation, and they're conjugated with cancer targets and they become very effective. So the FDA has approved two agents, lutetium dotatate for neuroendocrine cancer, and lutetium vipivotide for prostate cancer. And these drugs have made a big difference in patients with neuroendocrine and prostate. The only problem is that because they're effective, people are giving them much earlier in the disease course. And so these patients are living longer, and now these radioisotopes are given intravenously. So they bathe your stem cells and your blood cells with these type of radiation-emitting particles. And that's what concerns us. We are seeing more and more therapy-related clonal hematopoiesis, and the rates of MDS, AML are not only increasing, but they're of concern given that these patients are living longer.

Robin Huiras (07:36):

Thanks for breaking that down a little bit for us, Dr. Patnaik. I just kind of wanted to dig in a little bit to the types of cancers that patients who may go on to develop this manifestation of clonal hematopoiesis may have. Are there specific cancers that are more likely to be related?

Dr. Patnaik (07:56):

So that's a great question because clonal hematopoiesis occurs in the stem and progenitor cells, depending on the types of genes and the type of progenitor cells involved, broadly, clonal hematopoiesis can be a precursor to myeloid malignancies and lymphoid malignancies. The lymphoid malignancies include cancers such as chronic lymphocytic leukemia and non-Hodgkin's lymphoma, but the myeloid malignancies largely center around MDS or myelodysplastic syndrome, and AML or acute myelogenous leukemia. And the therapy-related ones are almost always in this myeloid spectrum, where they cause high-grade myelodysplastic syndrome or AML. They have a lot of genetic damage in the form of chromosomal damage, and our success rate in treating those leukemias is very poor. They just don't respond to therapy. So effectively, if this complication were to occur, it shortens the lifespan of the individual, making the treatment of the primary disease more grievous than the endurance of the same.

Robin Huiras (09:01):

Yeah, that sounds very concerning for patients who might be facing this future. I'm wondering, can you explain, I mean, this may seem obvious, but can you explain just a little bit more about why hematologists or oncologists should care about identifying these clones before there is evidence of overt disease?

Dr. Patnaik (09:20):

Yeah, I think there's a broader question of population screening and population impact, which I won't get into, but what I wanted to focus on is the cancer patient population. For decades, we have known that when we treat breast cancer, ovarian cancer, or any other treatment that's directed involving chemo-radiation therapy, there was a risk for patients to develop A: low blood counts, and B: myelodysplastic syndrome and leukemia. The problem was still we understood clonal hematopoiesis, we just did not know who was going to get this. And many patients that I've taken care of with therapy-related leukemia do not even remember being counseled about the risk that this could happen. So they would go in, for example, get treated for their breast cancer two years later, end up on the leukemia ward with leukemia and eventually die a few months later because of how aggressive these leukemias were.

And so that was personally very troubling for me. Why are some getting it, not others? And how do we do better at informing these individuals that they have a risk and incorporating that risk stratification in their discussion with their oncologists? And so the field of CH, or clonal hematopoiesis, when it came about, it really gave us a good opportunity to understand and baseline who is at risk for some of this happening with longitudinal tracking, who is now going on to develop it. So point number one, I think with this information, we are better able to educate and empower patients about their individual risk for treating one type of cancer with another. Number two, because medicine has evolved and is evolving rapidly, it allows the oncologist or the treating provider to incorporate this information in choosing the best available treatment. So if the patient has a risk for leukemia and there's an alternative agent like an immunotherapy or an antibody that's less likely to cause that clone from growing, then that decision-making is there.

But most importantly, can we find through clinical trials and other strategies, ways of mitigating these clones from growing or even eliminating them? That is why this area is of very special focus to Mayo Clinic and to our clonal hematopoiesis program.

Robin Huiras (11:48):

Do you have an example of a patient in your own practice that you've been able to help counsel through this issue, whether it's an alternative therapy or just informing their risk? Any cases that you might be able to share?

Dr. Patnaik (12:04):

Yeah, I think the latter is happening every day. So we are working very closely with our colleagues in oncology and even in hematology, where they go on to get treatments like cellular therapies or transplants, where the same thing can happen in myeloma/lymphoma. And so I think we have a clinic called the CHIP clinic, which is held weekly, and we talk to these patients, we educate them, empower them, understand their baseline risk, and make sure we communicate this to their primary treating doctor. So that first step, I think we've clicked the checkbox. We still have to scale because we are not touching everybody yet, but we are doing a much better job of at least the higher-risk patients, getting them in and talking to them. I think the second part has gotten better because, initially when we would find CHIP, the oncologist would say, OK, you found it, you can't treat it, but what do I do?

I have to treat the underlying cancer, which is a fair point. And many of those patients, we had to just say, OK, let's move ahead and see what happens. But as of today, as I said, especially for example, in myeloma or non-Hodgkin's lymphoma, CAR-T therapies seem to select for more CHIP, whereas bispecific antibodies are less likely and both are now options on the table. And so recently there were patients where the presence of CHIP helped the physician decide between CAR-T versus a bispecific. And I think this is going to keep growing. We have seen that there are small molecule inhibitors, there are various gene editing strategies that are coming through, and I think all of this will interplay nicely when this information is provided to the patient and the treating physician.

Robin Huiras (13:54):

Yeah, thanks so much for providing those examples. I really think it really does exemplify how this test can help patients and their physicians choose the right therapy. Now I'd like to segue a little bit and move on to talk about the actual test for clonal hematopoiesis. Dr. Zheng, can we talk about some of the existing approaches that clinicians may be using today to identify clonal hematopoiesis? And then can you speak to some of the limitations of those methods?

Dr. Zheng (14:23):

Of course. Clinicians may identify clonal hematopoiesis through several approaches, including a standard myeloid NGS panel, bone marrow workups, including cytogenetic studies, prior molecular testing, and sometimes incidental tumor tissue testing or tumor liquid biopsy testing. These methods are clinically useful, but most were not designed specifically for high sensitivity clonal hematopoiesis detection or longitudinal monitoring. So the standard myeloid NGS panel typically have limited detection of around 2–5%, so they may miss low-level clones. This matters because small therapy-selected clones can expand under treatment pressure, as Dr. Patnaik has just discussed, and they can become clinically significant. In addition, these conventional panels may not fully cover therapy-relevant DNA damage response genes, such as PPM1D, ATM, CHEK2, and BRCA1 and 2. And finally, liquid biopsy or tumor tissue sequencing, this can detect potential clonal hematopoiesis variants, but that can create uncertainty because some of those detected variants may come from hematopoietic cells rather than the tumor cells.

And without a highly sensitive clonal hematopoiesis assay, it can be difficult to solve that uncertainty with confidence.

Robin Huiras (15:52):

Thanks, Dr. Zheng. Let's talk a little bit about the genes on our panel, which I believe there are 37. Can you tell me how those genes were selected, and what do changes in these genes tell us about a patient's risk?

Dr. Zheng (16:06):

Yes. The 37 genes were selected based on the intended use of the assay, including detecting clonal hematopoiesis and clonal cytopenia and therapy-related clonal evolution. So we included canonical CH and myeloid genes such as DMNT3A, JAK2, ASXL1, and RUNX1, et cetera, as well as DNA damage response genes such as TP53, PPM1D, ATM, CHEK2, and also BRCA pathway genes. These are especially relevant in oncology patients, because as Dr. Patnaik has discussed, genotoxic therapy can select for these clones in these pathways. And the risk is assessed by integrating genes involved and their variety of frequency or the clone size and also number of variants, also blood counts, treatment history, and whether the clone is stable or expanding over time. To give you an example, a low-level DMNT3A clone carries a different risk than the large PPM1D clone after therapy.

Robin Huiras (17:13):

Thanks, Dr. Zheng, for talking a little bit about how the genes in our panel were specifically selected for their association with clonal hematopoiesis. I'd like to talk a little bit about the sensitivity of this assay. How does it compare to other clonal hematopoiesis tests that are on the market?

Dr. Zheng (17:30):

So high sensitivity means detecting very small clonal populations. So in practical terms, VAF, which is varient allele frequency, tells us how much of the blood DNA carries a mutation. So HSCHP, which is our assay, has a validated limit of detection of 0.25%. As a conventional approach, typically we have a limit of detection of 2–5%. And 0.25% variant allele frequency means 1 in 400 molecules. And one way to think about the high sensitivity is a difference between spotting a small spark versus waiting until you see a campfire. And the high sensitivity assay enables earlier detection, creating the opportunity to monitor whether small clones remain stable or expanding over time. So clinically this matters because higher sensitivity can provide more visibility into these emerging clones and improve confidence in a negative baseline result, and also support monitoring for clonal evolution and also help distinguish clonal hematopoiesis-associated variants from tumor-derived variants in liquid biopsy testing.

Robin Huiras (18:41):

Thanks, Dr. Zheng. Dr. Patnaik, I'm curious to know your thoughts on this question from a clinical perspective.

Dr. Patnaik (18:47):

Yeah, I think this is a very important aspect because, unlike hematological malignancies where we have access to the tumor from the blood and bone marrow, there's several solid tumors where biopsies are either not possible or be not sufficient or just too invasive for patients. And so the field of ctDNA, or circulating tumor DNA, cell-free DNA, or as you colloquially term them, liquid biopsies, is the future and already is something that is highly operational. As you can imagine, when you profile DNA in the plasma, it has multiple sources, not just the fraction that's being shed by the tumor, but also from endothelial cells, liver cells, and then, of course, the white blood cells. And I'll give you an example for prostate cancer. There is a class of drugs called PARP inhibitors, which we had spoken about earlier in the program, that has been approved for people who have mutations in this gene called BRCA1 or BRCA2.

And so there were cases where people would do the liquid biopsy, tell the patient, OK, you have a BRCA mutation, and prescribe the drug. Not realizing that in patients with prostate cancer over time, the white blood cells can develop BRCA mutations. Maybe even one in five people, if conservatively speaking, where you do a liquid biopsy, find a BRCA1 or BRCA2 mutation, actually don't have it in the tumor, but have it as CHIP. And so giving them treatment is actually not treating their prostate cancer, but is also exposing them to side effects and toxicities, number one. Number two, the solid tumor doctors are relying on this information to prognosticate. If they see a P53 mutation or if they see something that is deleterious, but if it's not coming from the tumor and it's from the CHIP aspect of the white blood cells, then that information is not being used appropriately.

So I think the ideal liquid biopsy would be a test where, apart from the plasma fraction, the white blood cells are also profiled for CHIP, and that is subtracted from the plasma fraction before we make a comment on whether a particular mutation belongs to the tumor or is it clonal hematopoiesis. And sometimes there could be hereditary mutations, too. And so, to make it even more comprehensive, understanding the germline, understanding the hematopoietic component and the tumor would be the most perfect way to interpret a liquid biopsy moving forward.

Robin Huiras (21:17):

So building on that just a little bit, Dr. Patnaik, how can these test results inform care across the whole of a patient's cancer journey? We talked a little about informed decision-making, but I'm wondering, does it assist with helping clinicians understand their baseline molecular risk at the beginning of their journey? Can it help them understand how often they need to be monitored for developing this disease? Can it help with clinical trial eligibility, for instance?

Dr. Patnaik (21:48):

Yeah, I think one thing to remember is that clonal hematopoiesis is a dynamic process. So what you obtain at baseline is not what's going to be there in six months or 12 months. So this is one of those tests where longitudinal tracking is very, very meaningful. Unlike hereditary panel, where what you're born with is unlikely going to change and you can live with that genome through your journey, this is going to evolve, it's going to become complex. The baseline assessment is very useful, as I said, because it identifies those patients that are likely going to be at higher risk. It also allows us to understand the cadence of testing. It also helps discuss risk benefits, alternatives at the time of starting treatment. But let's say we move ahead, some of these clones, which would be very tiny or may not even be detected at that time, may still emerge as we move forward.

Some may grow, some may shrink, some may acquire newer mutations. And so I think following that longitudinally, what we don't know is how often the interval should be, and that's what we are learning as we are going along with the process. And with regards to clinical trials, absolutely, there are several attempts, none of them have reached regulatory approval yet, but there are a lot of people, including ourselves, trying to understand, how can we prevent clonal expansions? How can we neutralize these pre-malignant clones, or how can we reduce their growth rate? So having a good test is the foundation to doing these clinical trials, and that makes us very excited.

Robin Huiras (23:24):

Yeah. And then again, just the whole idea of informed decision-making as a powerful tool to give patients the power to decide. Thanks, Dr. Patnaik, for sharing all of your insights based upon your experience. I'd like to take a step back, if you will, to focus on the broader view of this test. What do you view are the unmet patient needs that this type of testing is beginning to address?

Dr. Patnaik (23:50):

Yeah, I think one is we've not had a test like this, so it's a huge breakthrough. As Dr. Zheng has pointed out, to get that accuracy to pick up clones as low as 0.25% is kind of unprecedented. So to have that armament with us is now allowing us to identify all these patients who would've been missed had we used conventional NGS techniques. So now you're allowing or empowering, as I like to say it, a higher number of patients to understand what their baseline risk is. The accuracy and the genes that have been selected are also unique. This is not just a myeloid malignancies panel. We have spent a decade understanding which are the genes that are likely to grow under these selection pressures, which are relevant. And so trying to understand how they would longitudinally change now allows these patients the option of saying, "OK, I have this at baseline.

I still need this chemotherapy, but then can I at least be monitored and understand?" I'll give you an example, like PARP inhibitors in ovarian cancer are FDA-approved for between two years, sometimes three years, and not longer. A lot of women who take them do well and they see their primary cancer regress, and they don't want to stop it. We've had patients go on five, six, seven years saying, "This is working. Why would you curtail it?" But we have to counterbalance that with what's happening to their clonal hematopoiesis clones. So sometimes showing them that data saying, "OK, you've taken it for four years, but now look, this particular P53 mutation is growing, and your blood counts are becoming abnormal. You're really risking developing an aggressive blood cancer,” helps them with the decision-making process. So I think we've allowed with this test, the democratization of this knowledge beyond just research labs, this is a clinical test, number one.

Number two, this test is going to grow. We have already decided what the next population base is going to be. We're going to focus on those with hereditary predisposition. So there are inherited marrow failures and conditions that increase the risk of leukemia, where CHIP is usually the first step that predates leukemia by years. And so we're trying to see if that could be used as a screening tool. We're trying to see whether this has a role in inflammatory diseases and cardiovascular diseases. So this is truly a test that spans multiple divisions, departments, and truly will help several people across all facets of healthcare. It has to be used wisely, appropriately, and the right knowledge behind it. And so the last thing I'll say is, what we are focusing on as a group is genomic literacy. How do we increase awareness about the nuances of interpretation, not just amongst providers, but amongst our patients?

Robin Huiras (26:42):

That's just wonderful to hear, Dr. Patnaik. Thanks so much for sharing what the future holds for this type of testing. Dr. Zheng, I'm really curious to hear your thoughts from a laboratory perspective. What clinical needs does this assay meet?

Dr. Zheng (26:57):

The clinical need for the clonal hematopoiesis is really, as Dr. Patnaik mentioned, it's moving from an incidental finding to an intentional part of care, which require an intentional and sensitive approach, which can support risk assessment and follow-up planning. And from the lab perspective, I think the HSCHP, which is the name of this test, really addresses the need of having a dedicated and highly sensitive clonal hematopoiesis assay. And this is especially important for patients where the conventional approach may not provide sufficient resolution of sensitivity.

Robin Huiras (27:32):

Thanks so much for sharing your perspective on that, Dr. Zheng. Before we wrap up today, I'm hoping each of you can share your thoughts on what development in clonal hematopoiesis testing or patient care are you most encouraged by. Dr. Patnaik, let's start with you.

Dr. Patnaik (27:48):

Yeah, so I'll answer this with two hats. The first hat is my clinician hat. So as you know, I see these patients, and I've been doing that for the last two decades, and there are two important philosophical issues that this assay has helped me with. Number one is with informed consent. When I was a trainee, I remember in the leukemia service having two young women who had breast cancer who came to the hospital two years later with therapy-related AML and died on service. And that memory has never faded because I remember talking to them, both of them not remembering that this could be a risk of their breast cancer therapy, and for us being absolutely helpless in understanding, why did they get it and not others? And so to be able to take this front and center to now make sure that all these patients know that they have an option to understand their baseline risk truly encompasses what informed consent means.

The second tenement of medicine that I gravely respect is to do no harm. And I think what was bothering me was how these liquid biopsies and even liquid MRD assays were being interpreted without correcting for CHIP mutations. And that was very painful to watch. And I feel like with this ability now and with awareness, we will not unintentionally commit a patient to a therapy that they have no benefit from, but actually can be harmed. And with my research hat on, as Dr. Zheng pointed out, the potential is limitless. We go from inflammation, endothelial dysfunction, cardiovascular disease, oncogenesis, to even clinical trials. And this really fits the paradigm of early detection, early intervention. Can we catch it early? Can we intervene early? An intervention would encompass everything from enabling knowledge bases to actually therapy-based approaches.

Robin Huiras (29:58):

Great. Thanks, Dr. Patnaik. Dr. Zheng?

Dr. Zheng (30:01):

Yes. So what I'm mostly encouraged by is that CH is moving from incidental and late findings to a more intentional part of patient care. Now in oncology, CH can help us to assess the risk of therapy-related risks. And now we are learning that clonal hematopoiesis can have a broader biological effect. It can contribute to systemic inflammation, and CH-derived immune cells can enter tumor microenvironment and potentially influence the tumor biology and treatment outcome. And also, as Dr. Patnaik just mentioned, that beyond oncology, CH being increasingly studied in cardiovascular disease and other inflammation-associated conditions. High sensitivity clonal hematopoiesis assay is really a step forward to a broader precision medicine model because it provides a sensitive and structured way for us to detect and follow these clones.

Robin Huiras (30:55):

Thank you both so much for sharing your thoughtful and very patient-focused replies. I have learned so much today, and I sure hope our listeners have as well. I really do appreciate your time. To our listeners out there today, I hope you've enjoyed your time with us as well and will tune in again for our next installment of Diagnostics in Practice.