JCO Precision Oncology Conversations podcast

October 11, 2025 Lynch Syndrome Mortality in the Immunotherapy Era

JCO PO author Dr. Asaf Maoz at Dana-Farber Cancer Institute shares insights into article, “Causes of Death Among Individuals with Lynch Syndrome in the Immunotherapy Era.” Host Dr. Rafeh Naqash and Dr. Maoz discuss the causes of death in individuals with LS and the evolving role of immunotherapy.

TRANSCRIPT

Dr. Rafeh Naqash: Hello, and welcome to JCO Precision Oncology Conversations, where we bring you engaging conversations with authors of clinically relevant and highly significant JCOPO articles. I'm your host, Dr. Rafeh Naqash, podcast editor for JCO Precision Oncology and Associate Professor Medicine, at the OU Health Stephenson Cancer Center.

Today, I'm super thrilled to be joined by Dr. Asaf Maoz, Medical Oncologist at Dana-Farber Cancer Institute, Brigham and Women's Hospital, and faculty at the Harvard Medical School, and also lead author on the JCO Precision Oncology article entitled "Causes of Death Among Individuals with Lynch Syndrome in the Immunotherapy Era." This publication will be a concurrent publication with an oral presentation at the annual CGA meeting.

At the time of this recording, our guest's disclosures will be linked in the transcript.

Asaf, I'm excited to welcome you on this podcast. Thank you for joining us today.

Dr. Asaf Maoz: Thank you so much for highlighting our paper.

Dr. Rafeh Naqash: Absolutely. And I was just talking to you that we met several years back when you were a trainee, and it looks like you've worked a lot in this field now, and it's very exciting to see that you consider JCOPO as a relevant home for some of your work. And the topic that you have published on is of significant interest to trainees from a precision medicine standpoint, to oncologists in general, covers a lot of aspects of immunotherapy. So, I'm really excited to talk to you about all of this.

Dr. Asaf Maoz: Me too, me too. And yeah, I think JCOPO has great content in the area of cancer genetics and has done a lot to disseminate the knowledge in that area.

Dr. Rafeh Naqash: Wonderful. So, let's get started and start off, given that we have hosts of different kinds of individuals who listen to this podcast, especially when driving from home to work or back, for the sake of making everything simple, can we start by asking you what is Lynch syndrome? How is it diagnosed? What are some of the main things to consider when you're trying to talk an individual where you suspect Lynch syndrome?

Dr. Asaf Maoz: Lynch syndrome is an inherited predisposition to cancer, and it is common. So, we used to think that, or there's a general notion in the medical community that it is a rare condition, but we actually know now from multiple studies, including studies that look at the general population and do genetic testing regardless of any clinical phenotype, that Lynch syndrome is found in about 1 in 300 people in the general population. If you think about it in the United States, that means that there are over a million people living with Lynch syndrome in the United States. Unfortunately, most individuals with Lynch syndrome don't know they have Lynch syndrome at the current time, and that's where a lot of the efforts in the community are being made to help detect more individuals who have Lynch syndrome.

Lynch syndrome is caused by pathogenic germline variants in mismatch repair genes, MLH1, MSH2, MSH6, or PMS2, or as a result of pathogenic variants in EPCAM that cause silencing of the MSH2 gene.

Dr. Rafeh Naqash: Excellent. Thank you for that explanation. Now, one of the other things I also realized, similar to BRCA germline mutations, where you require a second hit for individuals with Lynch syndrome to have mismatch repair deficient cancers, you also require a second hit to have that second hit result in an MSI-high cancer. Could you help us understand the difference of these two concepts where generally Lynch syndrome is thought of to be cancers that are mismatch repair deficient, but that's not necessarily true for all cases as we see in your paper. Can you tease this out for us a little bit more?

Dr. Asaf Maoz: Of course, of course. So, the germline defect is in one of the mismatch repair genes, and these genes are responsible for DNA mismatch repair, as their name implies. Now, in a normal cell, we think that one working copy is generally enough to maintain the mismatch repair machinery intact. What happens in tumors, as you alluded to, is that there is a second hit in the same mismatch repair gene that has the pathogenic germline variant, and that causes the mismatch repair machinery not to work anymore. And so what happens is that there is formation of mutations in the cancer cell that are not present in other cells in the body.

And we know that there are specific types of mutations that are associated with defects in mismatch repair mechanisms, and those are associated a lot of times with frameshift mutations. And we have termed them ‘microsatellites’. So there are areas in the genome that have repeats, for example, you know, if you have AAAA or GAGA, and those areas are particularly susceptible to mutations when the mismatch repair machinery is not working. And so we can measure that with DNA microsatellite instability testing. But we can also get a sense of whether the mismatch repair machinery is functioning by looking at protein expression on the surface of cancer cells and by doing immunohistochemistry. More recently, we're also able to infer whether the mismatch repair machinery is working by doing next-generation sequencing and looking at many, many microsatellites and whether they have this DNA instability in the microsatellites.

Dr. Rafeh Naqash: Excellent explanation. As a segue to what you just mentioned, and this reminds me of some work that one of my good friends, collaborators, Amin Nassar, whom you also know, I believe, had done a year and a half back, was published in Cancer Cell as a brief report, I believe, where the concept was that when you look at these mismatch repair deficient cancers, there is a difference between NGS testing, IHC testing, and maybe to some extent, PCR testing, where you can have discordances. Have you seen that in your clinical experience? What are some of your thoughts there? And if a trainee were to ask, what would be the gold standard to test individuals where you suspect mismatch repair deficient-related Lynch syndrome cancers? How would you test those individuals?

Dr. Asaf Maoz: We do sometimes see discordance, you know, from large series, the concordance rate is very high, and in most series it's over 95%. And so from a practical perspective, if we're thinking about the recommendation to screen all colorectal cancer and all endometrial cancer for mismatch repair deficiency, I think either PCR-based testing or immunohistochemistry is acceptable because the concordance rate is very high.

There are rare cases where it is not concordant, doing multiple of the tests makes sense at that time. If you think about the difference between the tests, the immunohistochemistry looks at protein expression, which is a surrogate for whether there is mismatch repair deficiency or not, right? Because ultimately, the mismatch repair deficiency is manifested in the mutations. So if the PCR does not show microsatellite instability and now NGS does not show microsatellite instability, the IHC may be a false positive. At the end of the day, the functional analysis of whether there are actually unstable microsatellites either by PCR or by NGS is what I would consider more informative. But IHC again is an excellent test and concordant with those results in over 95% of cases.

Now there is also an issue of sampling. It's possible that there's heterogeneity within the tumor. We published a case in JCOPO about heterogeneity of the mismatch repair status, and that was both by immunohistochemistry, but also by PCR. So there are some caveats and interpreting these tests does require some expertise, and I'm always happy to chat with trainees or whoever has an interesting or challenging case.

Dr. Rafeh Naqash: Thanks again for that very easy to understand explanation.

Now going to management strategies, could you elaborate a little bit upon the neo-adjuvant data currently, or the metastatic data which I think more people are familiar with for immunotherapy in individuals with MSI-high cancers?

Dr. Asaf Maoz: Yeah, that's an excellent question and obviously a very broad topic. Individuals with Lynch syndrome typically develop tumors that are mismatch repair deficient or microsatellite unstable. And we have seen over the last 15 years or so that these tumors, because they have a lot of mutations and because these mutations are very immunogenic, we have seen that they respond very well to immunotherapy. And this has been shown across disease sites and has been shown across disease settings. And for that reason, immunotherapy was approved for MSI-high or mismatch repair deficient cancer regardless of the anatomic site. It was the first tissue-agnostic approval by the FDA in 2017.

And so there are exciting studies both in the metastatic setting where we see individuals who respond to immunotherapy for many years, and one could wonder whether their cancer is going to come back or not. And also in the earlier setting, for example, the Cercek et al. study in the New England Journal from Sloan Kettering, where they showed that neoadjuvant immunotherapy can cause durable responses for rectal cancer that is mismatch repair deficient. And in that series, the patients did not require surgery or radiation, which is standard of care for rectal cancer otherwise.

And there's also exciting data in the adjuvant space, as was presented in ASCO by Dr. Sinicrope, the ATOMIC study, and many more efforts to bring immunotherapy into the treatment landscape for individuals with MSI-high cancer, including individuals with Lynch syndrome.

Dr. Rafeh Naqash: A lot of activity, especially in the neo-adjuvant and adjuvant space over the last two years or so.

Now going to the actual reason why we are here is your study. Could you tell us why you looked at this idea of patients who had Lynch syndrome and died, and the reasons for their death? What was the thought that triggered this project?

Dr. Asaf Maoz: As we were talking about, we now know that immunotherapy really has changed the treatment landscape for individuals with Lynch syndrome, and that most cancers that individuals with Lynch syndrome do have this mismatch repair deficiency. But we also know that individuals with Lynch syndrome can develop tumors that do not have mismatch repair deficiency, and we call them mismatch repair proficient or microsatellite stable. And there was a series from Memorial Sloan Kettering showing that in colorectal cancer, about 10% of the tumors that individuals with Lynch syndrome developed did not have mismatch repair deficiency. In addition to that, we anecdotally saw that some of our patients with Lynch syndrome died of causes that were not mismatch repair deficient tumors. We wanted to see how that has changed since immunotherapy was approved in a tissue-agnostic manner, meaning that we could look at this regardless of where the cancer started, because we would anticipate that if the tumor was mismatch repair deficient, the patient would be able to access immunotherapy as standard of care.

Dr. Rafeh Naqash: Thank you. And then you looked at different aspects of correlations with regards to individuals that had an MSI-high cancer with Lynch syndrome or an MSS cancer with Lynch syndrome. Could you elaborate on some of the important findings that you identified as well as some of the unusual findings that perhaps we did not know about, even though the sample size is limited, but what were some of the unique things that you did identify through this project?

Dr. Asaf Maoz: The first question was what cause is leading to death in individuals with Lynch syndrome? And we had 54 patients that we identified that had died since the approval of immunotherapy in 2017, 44 of which died of cancer-related causes. And when we looked at cancer-related causes of death, we wanted to know how many of those were due to mismatch repair deficient tumors versus mismatch repair proficient tumors or MS-stable tumors. And we found, somewhat surprisingly, that 43% of patients in our cohort actually died of tumors that were microsatellite stable or mismatch repair proficient, meaning of tumors that are not typically associated with Lynch syndrome. This is not entirely surprising as a cause of death because we know that immunotherapy does not typically work for tumors that are microsatellite stable. And so in the metastatic setting, there are much less cases of durable remissions with treatment. But it was helpful to have that figure as an important benchmark.

There are previous studies about causes of death in Lynch syndrome, and particularly from the Prospective Lynch Syndrome Database in Europe. Those have provided really important information about cause of death by cancer site, but they typically don't have mismatch repair status and are more difficult to interpret in that regard. They also don't include a large number of individuals who have PMS2 Lynch syndrome, which is the most common, but least penetrant form of Lynch syndrome.

Dr. Rafeh Naqash: As far as the subtype of pathogenic germline variants is concerned, did you notice anything unusual? And I've always had this question, and you may know more about this data, is: In the bigger context of immunotherapy, does the type of the pathogenic germline variant for Lynch syndrome associated MSI-high cancers, does that impact or have an association with the kind of outcomes, how soon a cancer progresses or how many exceptional responders perhaps with MSI-high cancers actually have a certain specific pathogenic germline variant?

Dr. Asaf Maoz: That's an excellent question, and certainly we need more data in that space. We know that the type of germline mutation, or the gene in which there is a germline pathogenic variant, determines to a large degree the cancer risk, right? So we know that individuals who have germline pathogenic variants in MLH1 or MSH2 have a much higher colorectal cancer risk than, for example, PMS2. We know that for PMS2, the risks are more limited to colorectal and endometrial, and may be lower risk of other cancers. We also know that, you know, the spectrum of disease may change based on the pathogenic germline variants. For example, individuals who have MSH2 associated Lynch syndrome have more risk of additional cancers in other organs like the urinary tract and other less common Lynch-associated tumors.

The question about response to therapy is one where we have much less information. There are studies that are trying to assess this, but I don't think the answer is there yet. Some of the non-clinical data looks at how many mutations there are based on the pathogenic variant and what the nature of those mutations are, whether they're more frameshift or others. But I think we still need more clinical data to understand whether the response to immunotherapy differs.

It's also complicated by the fact that the immunotherapy landscape is changing, especially in the metastatic setting, now with the approval of combination ipilimumab and nivolumab for first-line treatment of colorectal cancer that is microsatellite unstable. But in our study, we did find that, as you would expect, there is an enrichment in MS-stable cancers among those with PMS2 Lynch syndrome. Again, our denominator is those who died, right? So this is not the best way to look at the question whether this is overall true, that is more addressed by the study that Sloan Kettering published. But we do see, as we would anticipate, that there are more microsatellite stable cancers among those with PMS2 Lynch syndrome that died.

Dr. Rafeh Naqash: A lot to uncover there for sure. This study and perhaps some of the other work that you're doing is slowly advancing our understanding of some of these concepts.

So I'd like to shift gears to a couple of provocative questions that I generally like to ask. The first is, in your opinion, and you may or may not have data to back this up, which is okay, and that's why we're having a conversation about it. In your opinion, do you think the type or the quality of the neoantigen is different based on the pathogenic germline variant and a Lynch syndrome associated MSI-high cancer?

Dr. Asaf Maoz: I think there are some data out there that, you know, I can't cite off the top of my mind, but there are some data out there that suggest that that may be the case. I think the key question is the quality, right? I think that whether these differences that are found on a molecular level also translate to a clinical difference in response is something that is unknown at this moment. Some people hypothesize that if the tumor has less neoantigens, there's less of a response to immunotherapy. But I think we really need to be careful before making those assertions on a clinical level. I do think it's a really important question that needs to be answered, among others because, you know, in the colorectal space, for example, where we have both the option of doing ipilimumab with nivolumab and the option of doing pembrolizumab, we don't really know which patients need the CTLA-4 blockade versus which patients can receive PD-1 blockade alone and avoid the potential excess toxicity of the CTLA-4 blockade. There are a lot of interesting questions there that still need to be answered.

And of course, individuals with Lynch syndrome are just a fraction of those individuals who have MSI-high cancer. So there's also the question about whether non-Lynch syndrome associated MSI-high cancer responds differently to immunotherapy than Lynch syndrome associated MSI-high cancer. A lot of very interesting questions in the field for sure.

Dr. Rafeh Naqash: Absolutely. My second question is more about trying to understand the role of ctDNA, MRD monitoring in individuals with Lynch syndrome. If somebody has a germline, you know, Lynch syndrome MSI-high cancer, when you do a tumor-informed ctDNA assessment, what do you capture generally there? Because, and this question stems from a discussion I've had with somebody regarding EGFR lung cancer, since I treat individuals with lung cancer, and the concept generally is that even if the tissue showed EGFR, but for MRD monitoring, when you do a barcoded sequence of different tumor specific mutations, it's not actually the EGFR that they track in the blood when they do ctDNA assessment. But from a Lynch syndrome standpoint, if you have a germline, right, which is the first hit, and then you have the somatic in the tumor, which is the second hit, are you aware or have you tried to look into this where what is exactly being followed if one had to follow MRD in a Lynch syndrome MSI-high colorectal cancer?

Dr. Asaf Maoz: I think a lot of the MRD assays are proprietary, and so we don't receive information about what the mutations that are being tracked are. In general, the idea is to track mutations that we would not expect to disappear as part of resistant mechanisms. We want these to be truncal mutations. We want these to be mutations in which resistance is not expected to result in reversion mutations. But what specifically is being tracked is something that I don't know because these assays, the tumor-informed ones, are proprietary, and we don't get the results regarding specific mutations. When it's circulating tumor DNA that is not necessarily tumor-informed, we do get those results, but that is less so about the specific selection of mutations.

Dr. Rafeh Naqash: Thank you for clarifying that question to some extent, of course, as you said, we don't know a lot, and we don't know what we don't know. That's the most important thing that I've learned in the process of understanding precision medicine and genomics, and it's a very fast-paced evolving field.

Last question related to your project, what is the next step? Are you planning any next steps as a bigger multicenter study or validation of some sort?

Dr. Asaf Maoz: There are two big questions that this study raises. One, is this true across multiple other sites, right? Because this is a single center study, and we really need additional centers to look at their data and validate whether they are also seeing that a substantial portion of deaths in individuals with Lynch syndrome are attributable to mismatch repair proficient cancer.

The other question is whether we can look at specifically MSI-high cancer versus MS-stable cancer and understand what the mortality rate for each of those are. From a clinical perspective, it's important to counsel individuals with Lynch syndrome about general cancer screening outside of mismatch repair deficient tumors and to understand that there is also a risk of mismatch repair proficient tumors and that treatment for those tumors would be different.

There's a lot of work to be done in the future. Another major area of need is to see whether tumors that are microsatellite stable can be sensitized to immunotherapy, and that is beyond the Lynch syndrome field, but that is something that certainly would benefit these individuals with Lynch syndrome who develop mismatch repair proficient cancer.

Dr. Rafeh Naqash: That's very interesting to hear, and we'll look forward to seeing some of those developments shape in the next few years.

Now, I'd like to spend a minute, minute and a half on you specifically as a researcher, clinician, scientist. Could you briefly highlight - because I remember meeting you several years back as a trainee, with your interest in genomics, computational research - could you briefly tell us what led you to hereditary cancer syndromes based on your research and work? What are some of the things that you learned along the way that other early career investigators can perhaps take lessons from?

Dr. Asaf Maoz: Big questions there, thanks for asking. I got interested in the field of hereditary cancer syndromes when I came to the United States and started doing lab research in Stephen Gruber's lab at the time at USC. He's now at City of Hope. And my interest was originally looking at immunotherapy and immunology, but I went to the case conferences where we were learning about individuals with hereditary cancer, and those were kind of earlier days where we were still trying to figure out how to test and what the implications for these individuals would be.

And through fellowship, I was also very interested in that, and I did my senior fellowship years with Dr. Yurgelun here at Dana-Farber, who is the director of the Lynch Syndrome Center. And I I think it's the combination between being able to treat individuals based on precision medicine and what the germline mutation is, but also the ability to prevent cancer and to develop strategies to intercept cancer early that is really appealing to me in this field.

It's also a great field to be in because it's a small field. If you come to the CGA-IGC meeting, you'll be able to interact with everyone. Everyone is super collaborative, super nice, and I really recommend it to trainees. The CGA-IGC annual meeting is really a great opportunity to learn more and experience some of the advancement specifically in the GI hereditary space.

Lessons for trainees. I think there are a lot of lessons that I could think about, but I think finding strong and supportive mentors is one of the things that has helped me most. I think that just having close relationship with your mentor, having frequent discussions and honest discussions about what is feasible, what is going to make a difference for your patients and your research and what you want to focus on is really important. And so I think if I had to choose one thing, I would say choose a mentor that you trust, that you feel you have a good relationship with, and that has the availability to support you.

Dr. Rafeh Naqash: Thank you so much for those insightful comments, and thank you for sharing with us your journey, your project, and some of your interesting thoughts on this concept of hereditary cancers. Hopefully, we'll see more of this work being published in JCOPO through your lab or work from others.

Dr. Asaf Maoz: Thank you so much. I appreciate the opportunity to be here.

Dr. Rafeh Naqash: Thank you for listening to JCO Precision Oncology Conversations. Don't forget to give us a rating or review and be sure to subscribe so you never miss an episode. You can find all ASCO shows at ASCO.org/podcasts.

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, experience, 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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