Minimal residual disease in colorectal cancer — Update after ASCO-GI 22: Dr. Kopetz (2022)

Manju George 0:00
Hello everyone. Welcome to another round of talks. Today we have Dr Scott Kopec with us. He’s the professor at the Department of GI Medical oncology Division of Cancer Medicine at MD Anderson. He’s also the NCI Colon Cancer Task Force chair, and I don’t think that Dr kopetz needs much of an introduction to the people in Colontown. So thank you again for your time, and welcome.

Dr. Kopetz 0:26
Oh, thank you so much. These are always so much fun, and delighted to be able to to share some thoughts and hopefully have some great discussions here as well, acknowledging what we know and also what we don’t know about this field, which is rapidly evolving. So wanted to go through some background and kind of fundamentals here, and then try to talk about some of the areas. And I have a number of frequently asked questions at the end that we can use for discussion, and then go from there. So okay, so what are we talking about when we’re talking about circulating tumor DNA? And I see my idea here really is thinking about, how do we focus on minimal residual disease in colorectal cancer?So the I think, acknowledging that this is all enabled by just a tremendous technical advances and sequencing that really allow us to find the proverbial needle in the haystack that we’re looking for, a DNA fragment in circulation among just a tremendous amount of of normal DNA that’s shed on a daily basis into the blood, and that we can then see these very rare DNA fragments that, because of our understanding of of colorectal cancer, we know is coming from a cancer cell. Now this is enabled because we can sequence incredibly deeply, but also that we’ve gotten as a field, very good at not having errors in the sequencing, right? There’s been methodologies to improve it so we’re not dealing with as many sequencing errors as we did before. So the key point that I wanted to make is that there are a lot of liquid biopsy tests out there. This is not circulating tumor cells, so CTCs. So circulating tumor cells are ones that are not as sensitive in colorectal cancer where you’re actually seeing intact cells from from the cancer, we’re looking at fragments of DNA.

Dr. Kopetz 0:33
Theother key point is that what we’ll be talking about really is different from a molecular profiling circulating tumor DNAtest, ones that it’s really about what are the mutations that are present in the tumor and how they are they changing over time. We recognize now that there’s really two different flavors of these tests, really, MRD circulating tumor DNA tests versus the molecular profiling, right? So you’ll see things like, Foundation One, Guardant 360s things like that, that are really designed to be more molecular profiling, but are not the ones that we’ll be talking about today, that are more designed for minimal residual disease. Now, why am I excited by this.

Dr. Kopetz 3:04
What we see is that the assay is really a next leap in sensitivity, and I kind of put this in perspective. It’s all about how many cancer cells are in the body before we can detect it, right. And, in in best case scenario, a chest X ray may be able to detect a billion cancer cells, right? And we were excited as a field with the leap into CT technology, right? That allowed us to have a two log improvement, at least,in the sensitivity of what we can detect, and now we are recognizing this is another several log improvement and sensitivity, meaning 100 fold or better sensitivity for these and that we can detect, a much smaller amount of cancer cells. Now these numbers are gross estimates, and there’s a lot of variability and other things that impact this so we use this term minimal residual disease just to mean that the presence of cancer cells or cancer in the body below the limits of detection. So if we kind of use those numbers from the prior slide and put them here on the Y axis, you can kind of see around 10 to the seventh, we can start to detect things by CT scans, and that there’s a proportion down below that are not detectable by imaging. And then at some point, there’s zero tumor burden. So there’s a little hash marks there where it’s zero cells in the body. And that, of course, defines cure. And so we think about this concept of, well, there’s a space below where there’s cancer cells in the body, below what we can detect. And we call that minimal residual disease terminology. And that’s kind of key, no radiographic evidence of disease. Now, I’ve now built, as you can see, that there are, we’re talking about a proportion of minimal residual disease that we can actually detect by CtDNA. This is a great improvement, but it’s not that we can detect down to one or two cells in the body, right? So there’s still a proportion of patients that may have 1000 cancer cells in the body or or a lower amount of disease that we may not we still can’t detect by either imaging or CtDNA. So, so this is a great advance, but it’s not perfect, and we’ll talk about this a little later.

Dr. Kopetz 6:15
What does it mean when we do this? Okay, so let’s talk about how these perform, right, and what do these mean? Well, these curves, I know that are very common and and we’ll come back and reiterate a little more detail a little later, a kind of a refresher on these, what we call Kaplan Meier or survival curves. But what this tells us is the the amount of patients that have survived without any evidence of disease over time, depending on what category they were in the post op settings. So in patients that had stage three colorectal cancer, where there was immediate post op test that was done, we can see, and these are some early data. Here we can see those patients that had detectable CtDNA, but nothing on scans, what we see in the orange line is just as time elapses, a number of these patients then had disease appearing on the scan. And this is actually percent survival without recurrence. So this is as patients recur. You can see each of these little drop downs is a patient that is having a recurrence, and you can see that a key feature of this is that there’s a near 100% positive predictive value. What does that mean? It means if there’s positive test that was seen post operatively, it may take two years for things to appear, or in this last patient, even three years. But these are patients that at some point radiographically reccurred. We didn’t have any patients in these, many of these series that did not, with sufficient follow up. So these, we talked about these curves going all the way down to the bottom. But we also recognize that the sensitivity for a single test is not, it’s not perfect, as we mentioned on that last slide, that there’s a some that we can detect, but some that we can’t because it may still be too low from our level of detection. And for a single test, we talk about maybe about a 50%, some series as high as 70%, but I think 50 is kind of a good number to think about sensitivity here, which means that there are still patients that, with a single test you may may miss, right, that they were at perhaps lower levels of disease, but then the disease kind of grew over time, and maybe several years later, the disease recurred. So that’s why we’ll kind of think a little bit about the idea of serial testing in a little bit there as well. And then we’ll talk more about this idea of, well, how long does it take between the time you have a positive test and things appearing radiographically. And this varies widely by series, but just another concept that we’ll talk about. So the idea now, back to our graph here is that, can you take a patient, that had disease that was visible, resected, and maybe resection and adjuvant, but we’ll just talk about some definitive treatments here.

Dr. Kopetz 6:33
And there’s two scenarios that you can see right there is the patient who had all the tumor removed, and it was, the patient was cured, or patients that had disease that was removed and that nothing seen on scan, say they were in remission, NED, no evidence of disease, but detectable by CT DNA, and it’s a matter of time until it appears by imaging. And that’s kind of the concept that we’re we’re getting at.

Dr. Kopetz 10:20
So there are some commercially available assays. There’s kind of two major ones that are being utilized now. We won’t really get into a lot of the details of the differences between the assays, although happy to discuss that if of interest. There’s the Guardant health REVEAL assay and the Signatera from the Natera assay, and there’s undoubtedly more coming in the next year. These are currently covered by Medicare and most insurance companies for colorectal cancer, not necessarily for other GI cancers. So what we’ll be talking about today is really kind of colorectal cancer specific. Now we have some updated data, the Japanese cohorts. Dr Kotaka presented CIRCULATE Japan. Investigators have a very large prospective cohort that they’ve been accumulating. I won’t go through all the details, but what we’ll be presenting is this kind of observational cohort where they hope to accrue over 5000 patients to really understand the natural history of this. And this was an early update of 1000 patients in this analysis here, they were looking at a number of different factors, and I’m just going to highlight a few things that I think are relevant. So don’t get overwhelmed by all the arrows and the numbers here, where we put a very large patient population. So this is about 10 times larger than a lot of the other series that we’ve seen to date. Now the outcome, the data updates, we don’t have a lot of mature data, so this is only about 18 months of follow up here. But what you can see is when you look at that immediate post op, CtDNA. So this is regardless, this one whether or not they got adjuvant therapy. We’re just looking post op for all stages, one through four. Here you can see a separation of the curve.

Dr. Kopetz 12:24
As we showed before, the patients that are CtDNA positive, you can see here we would expect over time, given more follow up, that that would continue down based on the data I showed you previously, and the absence of any adjuvant therapy. And then you can see the patients that did really well when they were negative, but still some patients that were having some recurrence. Now, if we focus just on stage two-three, you notice it’s really not a whole lot different, right? So going back and forth between the two, and I think this is a key point, is that we talk about how important stage is, but CtDNA looks like a really strong prognostic marker, right? And, I would say I would much rather have a stage four cancer that has been resected and I’m CtDNA negative, then have a stage two cancer that’s been resected, and I’m CtDNA positive, right? So that this idea of stages, it’s something we’re really starting to think about, like, is CtDNA even a stronger predictor than stage of disease? Now, the other data that we can talk about here and again, I don’t want to dive too much into the weeds, but really kind of thinking about, well, what about patients who then went on to get some adjuvant therapy and had changes in dynamics. So what you can see is that if you were able to get to negative with some adjuvant chemotherapy, for example, here in the green line, even if you’re positive before, things look really good, right? You’re almost on top of the line of patients that were immediately negative. Now we’ll need more follow up there. But if you were either positive and remain positive and blue, or were negative, but then developed positive, you can see the recurrence rates are higher, meaning the lower curves. Alright, final curve, and then we’ll kind of dive, kind of zoom back up to the higher level discussions. But, but the final one is this idea of kind of clearance rate with the chemotherapy. And so these are observational cohorts, meaning this weren’t randomized studies, which would be the highest quality. But what you can see is that with adjuvant chemotherapy, about 70% of patients at the end of six months were able to have clearance of their CtDNA, right? It pushed it below the level of of detection now. But there’s also a small proportion of patients– there’s like, four or five different cohorts here. I think it’s actually a smaller number, like maybe about 10 patients or so that were positive at some point early on, did not get any adjuvant therapy, but then actually had cleared spontaneously by about six months. So just acknowledging that there is a proportion here that we still need to better understand, a few percent of that thing can happen.

Dr. Kopetz 15:39
So how do we use this test? So if we go back to this curve that we had before, and think about patients that have detectable by CtDNA setting here, one question is, is adjuvant therapy needed, right? And traditionally, we’ve given adjuvant on the basis of stage of disease, right? But if you know, if I convinced you by what I showed you before, it’s really not so much about stage of disease. It’s really that CtDNA is such a strong prognostic factor that maybe that’s enough to really guide who should get adjuvant therapy or not. And so if somebody is CtDNA negative versus positive, that could be a very different scenario. So there’s a number of studies ongoing. There’s a COBRA study that’s been ongoing for a little while, led by NRG, that’s taking patients in stage two, where the decision was for no adjuvant chemotherapy, and then trying to understand the utility, randomizing to use the assay or not. So this is really high level, level one data to see if we can improve outcomes. And then there’s just now launching is what the CIRCULATE-US, which is a companion, or we’re collaborating with CIRCULATE Japan, T1 to three N1 stage three, so we consider a lower risk stage three colon cancer. We’re looking at the CtDNA and actually saying, if there’s no CtDNA detected, they are randomized to either doing the adjuvant like we would normally, or as we showed before, these are patients who do really well. So maybe what we need is just serial CtDNA right? As long as you remain CtDNA negative, there’s no need for adjuvant therapy. In the setting, we are probably over treating majority of those patients. But if at any point during that CtDNA is detected, either initially or during surveillance, then those patients would go on to get treated. Now there’s a second question about, could we escalate? Can we do something a little more intense on the to improve outcomes in those patients? So as I mentioned, this is kind of a jointly analyzed with the prospective Vega study that’s being done with CIRCULATE Japan.

Dr. Kopetz 18:03
So this is obviously very different, because we’ve always been taught as medical oncologist, if you have stage three colon cancer, you need adjuvant therapy. So here’s actually the data, the non randomized data coming out of Japan. These are all patients that were CtDNA negative after surgery, and this is stage two and three, so high risk two and three, and then asking the question, is there any evidence of better outcome in those patients who were treated with chemotherapy versus those that didn’t with adjuvant, with a negative CtDNA? And I think what you can see is that patients do very well. There are a few that still relapse, but there’s really no difference that we can discern yet with the role of of adjuvant therapy. So, that’s what we’ll be looking at here, and again, not randomized. So we need these studies to understand. There are other studies, and this is the DYNAMIC III being done in Australia and in Canada, just to be aware of very similar randomizing to either doing what you do normally, or to be CtDNA informed, and the clinician would say, I’m picking what we’re going to do, and discussion with the patient, no therapy, 5FU, single agent or combination. And then the informed one, the physician would still make the same call, and based on the pre planned they would kind of de escalate one level.

Dr. Kopetz 19:38
So if the oncologist and patients said, well, we’d probably do six months of five Fu, and the CtDNA test came back negative, then it would be, we’re going to do less 5FU or just no chemo at all. And then conversely, if they said, We’re not going to do anything, and it was positive, then they would escalate up their treatment intensity. So that’s the DYNAMICIII study. Now there is this additional question of, well, can we do better than adjuvant FOLFOX? Like, what can we do that could improve outcomes, and certainly being better at treating the right patients is important, but we also want to make sure that we’re improving outcomes for everybody, and that’s where a lot of our excitement, and I think the innovation is coming.

Dr. Kopetz 20:35
So there’s this phenomenon that we say, Okay, if you have less than 10 to the seventh tumor cells (10 million tumor cells) in your body, we can give adjuvant chemotherapy, and we can cure patients in that setting, right? We can take some degree of tumor burden and we can take it down and eradicate all the disease, right? But we also acknowledge that when a patient has metastatic disease that’s visible on a scan, they’ve passed some sort of threshold and passed our ability to actually cure the patients, right, aside from very rare subsets, MSI and immunotherapy, for example. But most settings, FOLFOX is not going to cure patients with with metastatic disease that’s visible on the scan. So we know that there’s a difference between treating patients here and treating patients here in terms of our ability to eradicate the disease. So there’s a lot of effort about novel therapeutics here that may extend life in this incurable state. But there’s a real enthusiasm, and I hope momentum building around. Well, if we can capture it down here, maybe we can actually cure patients. We can drive them down with novel therapeutics to be cured instead of extending life, but not curing patients there. So this is, I think, a really important point to understand about why early detection here may enable more novel therapies that may cure more patients, which is really what we want to do. So just share some of the things, some of the approaches.

Dr. Kopetz 22:24
So this is an example of a study that I’m privileged to be able to to coordinate– international study looking at these higher, stage two or three, that patients who’ve had surgery that are CtDNA positive using their kind of a proprietary assay that the BioNtech team is utilizing, patients go on to receive FOLFOX and then get randomized to either get the vaccine or not, in addition to the best available treatment, FOLFOX here as well. So looking then at the end, this is actually the same vaccine technology that BioNtech and Pfizer use for COVID, but it’s really being personalized to an individual patient’s tumors. These are ones that really have to have surgery in the center, or get to a center really quickly after surgery, where the studies are being done, because it’s not a whole lot of time in between the surgery and needing to get on to the study. But I think just an example here of novel therapies in that space.

Dr. Kopetz 23:38
So the other kind of question and opportunity here is, even after adjuvant therapy, if we drive it down, but don’t eradicate it, and we keep watching patients with serial testing, we may be able to catch them, catch the disease the MRD, before It gets to the incurable, detected by imaging, right? And so the idea, can novel therapies cure patients in this setting. And I won’t go through the details here, but this is a really efficient way to study minimal residual disease with this, and so the details here are not critical, but just to say it used to take us 1000 patients to do a study to ask whether or not a novel therapy in this setting works, right, when we were just having to treat a lot of patients to understand, and you just didn’t see many novel therapies, right? The only therapies we would test in an “adjuvant setting”, quote, unquote was things that worked in metastatic right? So it was like, well, let’s test Avastin, let’s test Cetuximab, irinotecan, regorafenib, and none of those really worked, right? And, but there wasn’t any interest, because it was being too high risk to put something completely novel, like a vaccine or cellular therapy or immunotherapy in that setting because a 1000 patients is a really expensive study and was deemed high risk, but the setting now allows us to do small interventions, right? Let’s, let’s try in 30 patients, patients that have CtDNA positive, nothing evident on the scans, but let’s try a novel therapy that looks really promising and generate momentum and see if we can actually cure some of these patients. And from a drug development perspective, this is good because we need partners, pharmaceutical and industry and the NCI to bring novel interventions together. So I think that’s exactly it.

Dr. Kopetz 25:50
This is a study that we did at MD Anderson, I to my knowledge, at least the first to to do this in in colorectal cancer, looking at a immunotherapy in the setting again, 15 patients to get an answer. But there are a number of these going on. There’s RAS mutated patients, or patients that have a RAS mutation in their tumor, they’re eligible for a vaccine study here in colorectal. And there’s actually an effort ongoing in pancreatic cancer, but a number of these ongoing. So we have an NK cell and Cetuximab that’s just getting ready to open if patients have an MSI high tumor. Studies looking at doing immunotherapy early. TAS102, is an agent that has a lot in common with 5FU. And so there is some hope thatbecause 5FU works so well for curing patients that perhaps TAS102, may also, so I think a lot of interest in that area. Weknow that certain things are associated with better outcomes, meaning that that lifestyle may indeed cause some mild CtDNA positivity to be eradicated, right? So if we’re saying, Oh yes, vitamin D, aspirin, diet and exercise is important in reducing a risk of recurrence. But what we’re meaning is that there are some patients that have some residual cancer cells in their body, MRD, but by these lifestyle, we can get the body to clear those on their own. So there’s a really intensive and this is good remote option for patients to really say, well, let’s just throw everything we know from epidemiology data, really motivate, get dietitian, nutritionist, exercise, guage and to kind of help walk patients through a really intensive program for a few months,

Dr. Kopetz 28:01
Personalized peptide vaccines are ongoing, and this is another one with immunotherapy targeting BRAF mutated patients, and I think a number of other ones in development. Then I will say there’s, this is a kind of a plug for some resources that some colleagues and I’ve helped develop because this is a really rapidly moving field, and so certainly, the COLONTOWN is a great resource for hearing about what studies are coming up in this setting? Well, there’s also a CRC MRD website here we’re trying to keep up to date with number of trials that are ongoing in this and we’ll have some additional resources that you can look at. And I’m so appreciative to a number of of great colleagues in this space. I think we have more contributors coming on, but certainly Dr. George and Annie as well, for their input. This is a priority for us at MD Anderson, just to acknowledge this is something that we’ve really been helping to push, and we now have said this is going to be our standard for any patient undergoing resection at MD Anderson, that this is systematically going to be checked, regardless of stage, and then with the idea that there are things that we can do. So if there are patients that are undergoing surveillance and have a positive test but nothing seen on the scan, there are a number of trials that are coming that could be considered.

Dr. Kopetz 29:41
So wanted in the last few minutes before questions, go through some of the frequently asked questions here and kind of highlight some of these. So first is, how do I interpret a positive or negative test? Like, how certain can I be? And, you know, we talked about the. Before, but just to reiterate, because I think this is so important, we have a single test that we’re checking at some point after surgery, or surgery and adjuvant. It has a sensitivity that’s around 50% just that’s a nice, easy number to remember. So that means if I actually have MRD if I’m one of the patients that has disease somewhere in the body, how likely will this test be to detect it? Right? And it’s about 50% so there’s one way to look at that and say, well, 50% is not great, right? I wish we had to detect everybody, you know, all the patients. This is still substantially better than a CT scan, right? So the CT scan is the best that we have, or CT and CEA, this is substantially better in terms of sensitivity. The recognition is that if you then say, well, I’m going to do serial CT DNA, how likely is it that I will detect it by serial testing, not just a single test, but every few months? Then that number goes up much higher, right? 80 plus percent of the time. That means that most of the time we’ll be able to detect it in the blood before it is seen on CT scans. Now the corollary is the positive predictive value. So if the test is positive, how likely is it that I really have it right? So, so that is a very high number, meaning that when we see that positive, and we can never say 100% nothing’s ever 100% but if the test is positive, how likely is it that I really have MRD? I think it’s fair to say that for many patients, we don’t have long term follow up, as we saw from the really early studies, some of these patients had a positive test, but it was three years until the disease showed up radiographically, right? So it may just take time. So this is a number that we think is probably higher than 95% but we’ll it’ll take time to really understand that better. It is high enough that many of us in the field think that this is appropriate to enroll on the clinical trials. The FDA and others agree. They say, yes, this is a this test is sufficiently accurate to identifying that positive predictive value that we think it’s reasonable to try cellular therapies and try something novel in this space.

Dr. Kopetz 32:35
Okay, so a little quick refresher. We went through this a little bit. But what do these survival curves mean? Right? Well, mean, right, when we’re talking about all this, a lot of physicians like to use survival curves to describe this. So just a quick summary, and I use the same curve that we had before. So this is, in this case, percent that are disease free survival, so free of disease. So what we’re looking at is everyone starts free of disease, and that over time, we kind of look at a number of of patients here. So there’s eight patients. I chose this because it’s a nice, small number. So there’s eight patients that at at six months, here, all of them were still free of disease, but that at maybe not month 10 here, nine or so in this cohort that you saw a positive, one patient recurred. So we would make a note, and kind of come down 1/8 here to 88% and then maybe a few weeks later, you can see another little ditzel over, and then another patient would recur. And so as more patients recur, that number kind of goes down further. The other thing you’ll see on these curves are little tick marks, right? So little things popping up the top here. And what that means is that that’s as far, that’s all the information that we have on that patient. So, maybe there’s a patient here that had one draw was negative two weeks later, you know, or a month later, talk to the team, was seen in clinic, and then, for whatever reason, just stopped following up with that clinic, and the team wasn’t able to contact them anymore. So we really don’t know what happened to that patient. So we add a little tick mark here, just to acknowledge that that’s lost information. And so this, you can look at it and say, well, most patients here are out around three years in this cohort, but you can see you start to lose information on those patients after about the three year time point. So anyway these are what are called Kaplan Meier curves, or or survival curves, is the other term that we use, all right.

Dr. Kopetz 35:06
Other questions here, if I have a positive test, how long until something appears on the scan? Now, this varies by a number of the studies, but we kind of think that it’s somewhere around, kind of the eight month or so to 12 month lead time. But there’s, for an individual patients, it can be, there’s a lot of variability around it. So it’s something that we’re trying to define a little better in the field, and it depends on a few things in these cohorts, like how good the assay is, how frequently the CT scans are being done, right? This is just showing, for an individual patient that CT recurrence here, for example, this patient was at about two years, but the CtDNA was detected at baseline. Now there are a few patients, you can see two of them here, where the CT scan showed something at 12 months, but didn’t show up in the blood until like 16 months, right? So, so we do miss some then as well.

Dr. Kopetz 36:16
So when positive, are patients always positive, right? So there are some patients that may be positive and then go negative to without treating. So kind of talked about some of the Japan data that happens in a few percentage of patients. Certainly, we see that in our clinic, where patients may be positive right at the limits of detection, maybe drip down below limit of detection, and for many patients, then subsequently will become kind of positive again. There is noise, so these are individual patients that are kind of being followed over time. You can see most of them, the amount in the circulation kind of keep going up. There are some that just kind of go down a little bit, back up again and then up again. So so we think that the majority of the time that within the noise of the assay that patients will have continued rise in the CtDNA then. But perhaps with a really intensive lifestyle intervention and diet and other things that patients are doing, maybe we’re seeing some of those clear on their own.

Dr. Kopetz 37:33
So what does it mean if I had a stage three, and I’m now a year and a half out, and I’ve been doing testing, and I’m negative, right? So this curve was one way to kind of look at it, is that, where are the recurrences happening, right? And so you can see some of the recurrences early on, and in this cohort, at least if they were 12 months out, you don’t really see a whole lot of change. And so I think the short answer is, we don’t quite know yet, what we’d like to have is these conditional curves, right? Given that I’m a year and a half out and I’m negative, like, what is my outcome moving forward, right? And a lot of the data that we have is really based on, from that initial one. So I think the short answer is that these are, it’s a very good situation to be in, to be this far out and negative, keep testing and keeping an eye on it, for the reasons that we discussed. But we don’t have great data to give you exact numbers, like, what’s the likelihood of it coming back, kind of at that point, and how does that impact it?

Dr. Kopetz 38:48
Okay, so I have been doing surveillance. I have a positive CtDNA test after completing all of my surgery and adjuvant therapy, at some point, can CtDNA tell me where the cancer is hiding? And the short answer is, No, it’s not like a CT scan, right? You just know it’s somewhere in the body. So then the question becomes, what do I do with that information? Right? Should I get more frequent CT scans? And I say, we don’t know the answer for that definitively, but that’s kind of common practice that a lot of us will say, Okay, let’s do more frequent imaging instead of a CT scan in a year. Maybe we need to start doing those every three or six months to monitor there more closely.

Dr. Kopetz 39:29
A really common question is like, oh my goodness, should I start some chemotherapy now? And this is a really importantquestion. It’s not an easy one to understand, but I’ll kind of share my perspective and how I counsel my patients around this. We talked before about there are some therapies that can cure patients with low levels of minimal residual disease, right? 5FU and oxaliplatin are the only agents that have shown to cure patients, eradicate the disease. Irinotecan has been studied and FOLFIRI regimen, the 5FU and irinotecan is not able to do it. Now, it’s a fascinating question, why can’t it cure the patient’s disease in that setting? Maybe it’s the type of immune response that’s generated to platinum versus, a topoisomerase, and some very nuanced differences we don’t know for sure, but even though in metastatic disease, they have very similar disease control rates and shrinkage, in adjuvant, it’s night and day. FOLFOX works. FOLFIRI does not. So the short answer to do I start FOLFIRI now is to say, unfortunately, despite our desire otherwise, FOLFIRI is not going to cure the cancer, right? Instead, what it’s going to do is we’re going to kind of take a treatment and instead of kind of observing, maybe do a trial, but observing, radiographic recurrence occurs, then start FOLFIRI.What one is doing is kind of starting FOLFIRI early and recognizing when the tumor recurs radiographically, it’s obviously refractory to FOLFIRI. It’s growing through FOLFIRI. So then you’re on to kind of second line therapy or other kind of treatments beyond that, assuming all these patients got FOLFOX before. So we don’t know, and there’s a lot of reasons to say maybe not, that starting FOLFIRI early is not really going to be beneficial in extending life in this setting and others. Stand Up to Cancer study, randomizing patients to observation versus FOLFIRI to help address that. But I would not recommend doing FOLFIRI outside of a clinical trial at this time, because I think it’s not really clear, despite our initial instinct to want to treat it, it’s not really clear that we’re going to improve outcomes for patients in that in that setting.

Dr. Kopetz 42:05
Another question, I have resected disease in the peritoneum, right? Is CtDNA useful for me? So this kind of gets at the idea that is there’s a lot of variability in how CtDNA is released in different parts of the body. And we think that CtDNA is really good for detecting liver, for example. Just have a lot of data on that, and there’s questions about, well, is a peritoneal sensitivity the same as lung versus liver? And there are some differences. And I think the data is still a little immature here. I think this is a really nice study that was done by a Spanish and Japanese group that looked at the different sites of disease and how much does CtDNA was released, and the correlation, and this is kind of a concordance, and the molecular testing and their sensitivity as a surrogate of how much is being released. And what you can see is that the liver and the peritoneum, at least, had a very similar amount. Lung there was a sense that there was lower levels that were released. So I think the short answer is we don’t fully know, but we do think that it can be useful for all of them. It’s just they may have slightly different sensitivities based on that as well. But there’s a number of other variables that impact the CtDNA shedding. So we know that that perhaps site of disease does, the proliferation rate may as well, is it a really indolent cancer? We have patients have really indolent and visible disease in the body that are CtDNA negative, just because this tumor cells are not really replicating very fast at all. And and so even visible disease, sometimes we’ll we’ll miss with these sensitive tests, just because of the factors like, like replication rate. So just acknowledging, humbly, our limitations here. We really don’t know that how the performance yet for all of these different sites.

Dr. Kopetz 44:24
All right, so just conclusions here. I think we really are encouraged by these assays. These assays bring tremendous value. We don’t exactly know how to fully use them, but we have a lot of enthusiasm by how we can improve outcomes for patients, better direct therapies. Just a bit of terminology. This is not a high risk marker. So sometimes we will talk about, oh, well, this says that patients are at high risk. Well, it’s really we are detecting disease, right? Even though it’s not with a CT scan, it’s with a blood test, we are detecting molecular persistence of disease. And so it’s just a little bit different about how we think about it and discuss this. I fervently believe that this is a tremendous opportunity to develop new therapies in this setting, and that this is the window where we have much lower amount of disease, that we may be able to cure patients if we can be smart enough about figuring out what the treatment is that would be the best fit for them. And so I’m really hopeful that we’re going to see a rapid acceleration in novel therapies in the setting and trials to really try to cure patients. Right? We want to cure patients. And can this assay help develop a setting there? And I’d say we have great support from industry. We have great support from the FDA to really develop this space. So, I think good momentum in that area. So really optimistic about it, but the same time, we are in this disruptive period where there’s people that understandably want more data before changing practice, where we don’t have level one randomized data for many of these questions. And so I think acknowledging that this is going to be a really kind of confusing time, and that it will take time for this, this technology, for us to understand how best to utilize it, and how to change our treatment guidelines on a result of that. So with that, hopefully left some additional time for for questions.

Manju George 46:42
Okay, thank you, Dr. Kopetz!. That was excellent. I mean, you’ve covered a lot of ground, so I think maybe I’ll ask one question, and then we can go through the list. So lots of what you said was applicable to early stage disease, right? We have a large population of people in COLONTOWN who are interested in using CtDNA after resection in Stage Four setting, like oligo, metastatic disease, how is that different from what you have talked about?

Dr. Kopetz 47:10
Yeah, absolutely. And I think stage four resected disease is identical to stage three resected disease that are positive, right? So, absolutely applicable, the positivity rates are higher. So instead of like 15% it’s kind of 40 to 50% positivity rates in stage four resected. But all these apply. A number of the smaller studies that are coming are allowing stage fourresected patients on and so I think it’s especially interesting and important for our resected patients with resected stage four disease. So thank you for pointing that out. I think the the biology is identical, the the application of the questions are really identical.

Manju George 47:55
Okay, so I think maybe because we have limited time, let’s start from the top of the questions and go through them. So the first one was, would like some information on when CtDNA is positive post surgery, but then clears during 12 cycles of FOLFOX, is there concern that the patient had the initial positive? I think you covered some of it.

Dr. Kopetz 48:13
Yeah. So the early data, at least the Japanese data suggests that at least 18 months out, the outcomes look just as good as if you were negative post surgery there. So we’ll need more data. My sense is probably is going to be a slightly a higher risk population than patients who are negative post surgery. But, really, it looks like, the FOLFOX is working in those patients and may be clearing the disease.

Manju George 48:46
Okay, so, can you speak about interpreting CtDNA negative and stage four, and if serial negative on CtDNA testing? I mean, how confident can people be that they’re safe? Or, you know, how long,

Dr. Kopetz 48:58
Right? Yeah. And I think, you know, a CtDNA negative when stage four, I think when we think about, the risk of recurrence is higher. That the sensitivity is still fairly good with a single, but again, 50% range. Serially negative increases that enthusiasm for good outcomes. But I think the the risk of there still being disease despite a negative test, is higher with a stage four patients than a stage two or three, but still lots of value there.

Manju George 49:36
Okay, and then is that time period they say that the most common chance of recurrence is like the first two years after adjuvant therapy, right? Is that also applicable to the stage 4 NED setting?

Dr. Kopetz 49:47
It is, it tends to be a little earlier, maybe a year and a half. But yes.

Manju George 49:53
Okay. And somebody had a question about how to interpret the values of the CtDNA test, like, for example, Signatera tests with the values in the 10s versus hundreds. Like, how could people interpret that?

Dr. Kopetz 50:06
Yeah, everything we’ve been talking about positive and negative is really, it’s present or not, right? So that’s the key distinction. The levels within the positive, we don’t know exactly how to interpret that information yet, and whether what that means, but it’s really anything versus nothing is the key distinction right now.

Manju George 50:34
Okay. And then there’s a question about using epigenetic markers, like in REVEAL versus Signatera. What are the advantages, disadvantages? Or what would you recommend if you had a choice?

Dr. Kopetz 50:44
Yeah, I mean, I wouldn’t go so far as to make a recommendation. I think they both have value. The Signatera is tumor informed, so that you’re looking at the signatures of your cancer. So very specific there, that the idea is that helps reduce the false positive rates. The REVEAL testing is kind of understanding what colorectal cancer in general looks like.Don’t just look at mutations, but other methylation factors, other epigenetic factors that may improve the performance there and in the sensitivity. So we don’t really know. We recognize that there are even other assays coming that will have other characteristics as well. So I wouldn’t recommend testing with both. I think it’s just kind of talk to your oncologist and figure out which one he or she has had good experience with and comfort, and doing one is sufficient, okay?

Manju George 51:48
And the next question is, what is like an ideal time interval for serial testing?

Dr. Kopetz 51:54
Yeah, so it’s reimbursed right now about every three months, and I think that’s a reasonable time frame, I don’t think more frequent testing would be useful.

Manju George 52:04
Okay, so this is I’m just going to summarize this question. So for people with stage four NED and who were negative initially for MRD and then turned positive, do you have any suggestions of what kind of chemo if they were exposed previously to platinum containing chemo. What would you suggest when it shows up again as positive later? Do you have any suggestions?

Dr. Kopetz 52:25
Yeah? So that’s the Yeah. That’s the kind of the hard part, because once patients have received six months of 5FUand a platinum, there’s not really any value of additional platinum and 5FU, so more FOLFOX won’t help cure the cancer and FOLFIRI, Cetuximab, irinotecan alone, Cape, Bev, all of those are not going to cure the cancer, unfortunately. So, that’s it’s really about trying to think a little outside of the box at that point, continue surveillance more frequently, but we’re not recommending doing any chemotherapy at that point, for the reasons that I mentioned before. It’s about it’s about recognizing what the goal of the therapy is at that at that point.

Speaker 1 52:26
Okay, so I’ll add one question here. So in quarantine, we generally recommend, when people have CtDNA positivity, to have like a liver MRI or things like that, and find out if the disease is localized so they can do localized treatment, like a resection. What’s your comment about?

Dr. Kopetz 53:33
Yeah, and I think that’s that’s good to take a look and try to understand where the disease is, because I think that’s the key, is that starting on FOLFIRI, for example, you don’t know where the disease is, that you’re you’re treating, and if there’s something that can be addressed surgically, that’s certainly a possibility.

Manju George 53:57
And then there’s this other question, do oncologists have a sense of which stage two and three patients progress to lung, liver or peritoneum? What are the factors, like sidedness or, tumor info? What would tell us what is more likely to happen?

Dr. Kopetz 54:11
Yeah, great, great question, and wish we had good understanding of that. We don’t. There’s some factors that are trends towards it, but they’re not sufficiently strong that we use that to help guide our surveillance. There’s still, a BRAF patient may be more likely to have peritoneal disease, but we’ll still have liver mats, so we are watching and surveilling all the above.

Manju George 54:11
Yeah, and then Annie’s other question, for the small percentage of CtDNA positive patients that spontaneously became negative. Do we know if they are MSI high?

Dr. Kopetz 54:46
Yeah, it’s a great question. Some of these may, indeed. The immune system may kind of kick in and recognize them and clear them. So you really hit the nail on the head. And one of the interesting questions out there is that, if there is a small percent of patients that are spontaneously clearing, why is that? And what can we learn from that? And it may be MSI high, it could be patients that have really gotten on the treadmill and done the diet and exercise or other things that may be doing the trick as well. So that’s, I think, that great opportunities for us to learn.

Manju George 55:19
Yeah, I thought it also said that the timing of when the first test is done, right? If it’s done too close to surgery, then you can get false positives. Do you think that’s also a possibility?

Dr. Kopetz 55:30
Yeah, it’s more false negatives right after surgery, right? So this is a needle on the haystack, and so we think about the concern of the haystack being too big, right? So if there’s, if you’re healing from surgery, there’s a lot of inflammation and that the the haystack is much bigger and it’s harder to find that needle. So you want that inflammation, normal DNA in circulation, to diminish with healing.

Manju George 55:59
Okay. So I think we’ll go back to this question. So a number of MRD trials using HLA testing to stratify patients to go on a vaccine, or CAR- T in BASECAMP. Is HLA testing, or Next Gen Sequencing something to really look at?

Dr. Kopetz 56:13
Yeah, it’s a great question. And how do we integrate some of those? Some of the vaccines are specific to certain HLA types, so that’s part of the screening. So, many of the studies though, will want to repeat the HLA testing with their own assay. So it may not be as useful to get that done on the NGS as it would otherwise. But I think it’s highlighting the high level of innovation in the space that are ongoing, looking at cellular therapies and and vaccines in this space, I think is, is really intriguing,

Manju George 56:54
Yeah. And then the trials that you mentioned. They’re open for both MSS and MSI high patients, right,

Manju George 57:02
orrect. Okay.

Manju George 57:03
Yeah, I was worried that we would be able to cover all the questions. So I have this one question. For surveillance versusFOLFIRI at progression, that would be relevant for KRAS, BRaf, who have only two chemo lines. Does that seem a legit concern?

Dr. Kopetz 57:23
Yeah, no, it’s kind of, the idea of using FOLFIRI early, and then, if progressing, then you’ve are now resistant to FOLFOX and FOLFIRI, so you have fewer lines of therapy remaining for treating radiographically evident metastatic disease. So Ithink yes, a legitimate concern, and that’s why we’re really hesitant to recommend outside of a trial, treating with FOLFIRI or other non-FOLFOX chemotherapy for CtDNA positive.

Manju George 57:57
Okay, so this other question, if NED on CT scan and positive on CtDNA, is there value to repeat CtDNA three months and look at up/down/ stable trend. Is a trend of any value?

Dr. Kopetz 58:10
Yeah, it so it’s a good question like, what information can you get out of the trend there? We don’t have enough information to know that. I do think kind of continuing monitoring still can be useful there, and it’s something that I do in my patients that are kind of positive, and NED on CT scan that trying to understand what’s going on. And we’ll commonly counsel patients on intensive lifestyle interventions and things like that that they can do. And so this kind of gives a readout, if any of that’s beneficial as well.

Manju George 58:47
Okay, I think we are at time. And thank you so much. This was very informative, and it covered everything so well. It’s always a pleasure to have you with us. Dr Kopetz.

Dr. Kopetz 58:56
Oh, it’s always a delight. And thank you so much for your organization and advocacy in the space,

Manju George 59:03
Okay, thanks everyone. Thank you for joining.