GI Cancer Research at ASCO25: Plenary Highlights and More

Jun 24, 2025

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Dr. Shaalan Beg and Dr. Kristen Ciombor discuss practice-changing studies in GI cancers and other novel treatment approaches that were presented at the 2025 ASCO Annual Meeting.

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Dr. Shaalan Beg: Hello, I'm Dr. Shaalan Beg, welcoming you to the ASCO Daily News Podcast. I'm a medical oncologist and an adjunct associate professor at UT Southwestern Medical Center in Dallas, Texas.

There were some remarkable advances in gastrointestinal cancers that were presented at the 2025 ASCO Annual Meeting, and I'm delighted to be joined by Dr. Kristen Ciombor to discuss some exciting GI data. Dr. Ciombor is the Ingram Associate Professor of Cancer Research and a co-leader of Translational Research and the Interventional Oncology Research Program at the Vanderbilt Ingram Cancer Center.

Our full disclosures are available in the transcript of this episode.

Dr. Ciombor, it's great to have you on the podcast today.

Dr. Kristen Ciombor: Thanks, Dr Beg. It's great to be here.

Dr. Shaalan Beg: Alright, let's kick it off. Big year for GI cancers. We'll start off with LBA1. This was the ATOMIC study sponsored by NCI and the National Clinical Trials Network (NCTN) and the Alliance group. This is a randomized study of standard chemotherapy alone or combined with atezolizumab as adjuvant therapy for stage III mismatch repair deficient colorectal cancer.

Dr. Kristen Ciombor: I think this study was really definitely practice-changing, as you can tell because it was a Plenary. But I do have some concerns in terms of how we're actually going to implement this and whether this is the final answer in this disease subtype. So, as you said, the patients were enrolled with stage III resected mismatch repair deficient colon cancer, and then they were randomized to either modified FOLFOX6 with or without atezolizumab. And that's where it starts to become interesting because not many of us give FOLFOX for 6 months like was done in this study. Obviously, the study was done over many years, so that was part of that answer, but also the patients received atezolizumab for a total of 12 months. So the question, I think, that comes from this abstract is, is this practical and is this the final answer?

I do think that this is practice-changing, and I will be talking to my patients with resected mismatch repair deficient colon cancer about FOLFOX plus atezolizumab. I think the big question is, do these patients need chemotherapy? And can we do a neoadjuvant approach instead? And that's where we don't have all the answers yet.

Dr. Shaalan Beg: Yeah, but it has been great to see immunotherapy make its way into the adjuvant space after having made such a big impact in the metastatic space, but still some unanswered questions in terms of the need for chemotherapy and then the duration of therapy, which I guess we'll have to stay tuned in for the next couple of years to to get a lot of those questions answered.

Dr. Kristen Ciombor: Yeah, but a big congratulations to the study team, to the NCTN, the NCI. I mean, this is really a great example of federally funded research that needs to continue. So, great job by the study team. The DFS 10% difference is really very large and certainly a practice-changing study.

Dr. Shaalan Beg: Yeah, and and sticking with colon cancer, and and this another federally funded study, but this time funded by a Canadian cancer clinical trials group was LBA3510. This is the CHALLENGE study. It's a randomized phase 3 trial of the impact of a structured exercise program on disease-free survival for stage III or high-risk stage II colon cancer. This study got a lot of buzz, a lot of mainstream press coverage, and a lot of discussions on what that means for us for the patients who we're going to be seeing next week in our clinic. What was your takeaway?

Dr. Kristen Ciombor: Yeah, this is a really interesting study, and I was so glad to see it presented because this partially answers one of the questions that patients always have for us in clinic, right? You know, once they've completed their standard chemotherapy and surgery, what else can they do to help prevent recurrence? And so we've always known and sort of extrapolated that healthy lifestyle habits are good, but now we have data, particularly in these patients. Most of them were stage III colon cancer patients, those had high-risk stage II cancer. And basically, the goal was to increase their physical activity by at least 10 MET hours per week. So, my big question, of course, as I came into this presentation was, "Okay, what does that mean exactly? How does that translate to real life?" And really what the author presented and explained was that basically most patients could hit their target by adding a 45- to 60-minute brisk walk 3 to 4 times a week. So I think this is very approachable.

Now, in the confines of the study, this was a structured exercise program, so it wasn't just patients doing this on their own. But I do think kind of extrapolating from that, that this is very achievable for most patients. And not only did this prevent recurrence of their prior cancer, but actually the rate of new primary cancer diagnoses, was less, which is really interesting, especially in the breast and prostate cancer. So this was a really interesting, and I think practice-changing study as well, especially given that this is something that most patients can do.

Dr. Shaalan Beg: Yeah, and there was a lot of discussion in the hallways after the presentation in terms of how this really changes our existing practice because most folks already recommend exercise as a way for improving outcomes in cancer patients. So we've already been doing that. Now we have some data on how much it can impact the benefit. But there was some discussion about what the actual degree of impact was. There was a drop-off rate in terms of how long folks were able to stick with this exercise regimen. But you've seen this in clinic when someone have their surgery, they have their chemotherapy, they've been so intimately involved with the oncology world, with the oncology practice, and they somehow feel that they're being let loose into this mean, angry world without any guidance and they're looking for something to do. "What more can I do in terms of my lifestyle?" And then here we have very solid data, as solid as can be for an intervention like exercise, showing that there is an impact and you can give a prescription for exercise when someone wraps up their chemotherapy for colon cancer, thanks to the study.

Dr. Kristen Ciombor: Yeah. It was a great study.

Dr. Shaalan Beg: Moving to gastroesophageal cancer, another late-breaking abstract. This is LBA5. The MATTERHORN trial was a phase 3 trial of durvalumab plus FLOT for resectable GE junction and gastric cancer. And again, another area where immunotherapy has made an impact, and here we're seeing it move closer for earlier-stage disease. What was your take-home for the MATTERHORN trial?

Dr. Kristen Ciombor: Yeah, so this study looked at neoadjuvant perioperative durvalumab plus our current standard chemotherapy of FLOT versus placebo plus FLOT. And this was a large study, almost 1,000 patients were randomized. And the primary endpoint was event-free survival, and it was definitely met in favor of the D + FLOT arm, as Dr. Klempner discussed after Dr Janjigian's presentation. I do think there are still some unanswered questions here. Overall survival is not yet mature, so we do have to wait and see how that shakes out. But it's very interesting and kind of is reflective of what, as you said, we're looking at earlier and earlier lines of therapy, particularly with immunotherapy, in these GI cancer spaces. So it makes a lot of sense to test this and and to look at this. So the toxicity was pretty similar to what we would expect. Primary endpoint was met, but again, we'll have to wait and see what the survival data looks like.

Dr. Shaalan Beg: Yeah, and in oncology, we know, especially for treatment that does add additional cost, it does add additional potential toxicity that we want to see that overall survival nudged. I did see some polls on social media asking folks whether their practices changed from this, and I think the results were favoring adding durvalumab for this group of patients but understanding that there are caveats to the addition of treatments and the eventual FDA approval in that indication as well.

Dr. Kristen Ciombor: Exactly. I completely agree with that.

Dr. Shaalan Beg: All right. How about we stick with gastroesophageal cancer? LBA4002 was trastuzumab deruxtecan versus ramucirumab plus paclitaxel for second-line treatment in HER2-positive unresectable or metastatic gastric cancer or GE junction cancer. This was the DESTINY-Gastric04 study. And again, antibody-drug conjugates making a big impact across different diseases. And here we have more data in the HER2-positive gastric cancer space. Your thoughts on this study?

Dr. Kristen Ciombor: Yeah, so this is a really important space in gastroesophageal cancer because the HER2 positivity rate is fairly high as compared to some of our other tumor types. So, I do think one of the important things was that patients did have biopsy confirmation of HER2 status, which was very important, and then they were randomized to either T-DXd versus the kind of second-line standard of ramucirumab-paclitaxel. So this was a great practical study and really answers a question that we had for a while in terms of does anti-HER2 therapy in the second-line really impact and improve survival. So we did see a statistically significant improvement favoring T-DXd. I do think it's always important to look at toxicity, though, too. And there was about almost 14% rate of interstitial lung disease, which of course is the most feared toxicity from some of these antibody-drug conjugates, especially T-DXd. So I do think it's important to keep that in mind, but this is definitely a great addition to the armamentarium for these HER2-positive patients.

Dr. Shaalan Beg: And pancreas cancer was on the stage after a very long time with a positive clinical trial. This is Abstract 4006. These were preliminary results from a phase 2 study of elraglusib in combination with gemcitabine/nab-paclitaxel versus gemcitabine/nab-paclitaxel alone for previously untreated metastatic pancreas cancer. This is a frontline clinical trial of gemcitabine/nab-paclitaxel plus/minus the study drug. There were other cohorts in this study as well, but they reported the results of their part 3B arm. And great to see some activity in the pancreas space. And your thoughts?

Dr. Kristen Ciombor: Yeah, we definitely need better treatments in pancreas cancer. This was a very welcome presentation to see. The elraglusib is an inhibitor of GSK-3beta, and it's thought that that mediates drug resistance and EMT. And so this is, I think, a perfect setting to test this drug. So patients basically were randomized. Patients with metastatic pancreas cancer were randomized 2: 1 to gemcitabine/nab-paclitaxel plus or minus this elraglusib. So, what we saw was that overall survival was better with the addition of this new drug. And overall, not only the 1-year overall survival, but also median overall survival.

The thing that was interesting, though, was that we saw that the overall survival rates were 9.3 months with the combination versus 7.2 months with just gemcitabine/nab-paclitaxel. And that's a little bit lower than we've seen in other studies. So, not sure what was going on there. Was it the patients that were a bit sicker? Was it a patient selection, you know, thing? I'm not really sure how to explain that so much. Also, the toxicity profile was much higher in terms of visual impairment, with over 60% of patients being treated with the combination versus 9% with gemcitabine/nab-paclitaxel. So these were mild, grade 1 and 2, but still something to be cautious about.

Dr. Shaalan Beg: And especially with this being a phase 2 trial, making sure that in a larger study we're able to better evaluate the toxicity and see if the control arm in the larger confirmatory study performs differently will be really important before this compound makes it to the clinic in our space. But very exciting to see these kinds of results for pancreas adenocarcinoma.

Dr. Kristen Ciombor: Yeah.

Dr. Shaalan Beg: We've talked, it seems, a couple of times on this podcast about the BREAKWATER clinical trial. We did hear PFS and updated OS data, updated overall survival data on first-line encorafenib plus cetuximab plus modified FOLFOX6 for BRAF-mutated colorectal cancer. This was LBA3500. And eagerly anticipated results – we have all previously heard the progression-free survival results – but here we heard updated overall survival results, and very well-received study it seemed from the audience that time. So what are your takeaways on the updated results for BREAKWATER?

Dr. Kristen Ciombor: In my opinion, this was one of the most practice-confirming studies. As you mentioned, we've already seen some of the preliminary data of BREAKWATER at prior meetings. But really what was particularly impactful for me was the median overall survival with the BREAKWATER regimen. So, again, patients received FOLFOX, encorafenib cetuximab in the first line if they had BRAF-mutated V600E-mutated colorectal cancer. And the median PFS was 12.8 months, which was actually really remarkable in this traditionally very aggressive, poor prognosis subtype of tumors. So, by seeing a median overall survival of 30.3 months was just incredible, in my opinion. Just a few years ago, that was considered the median overall survival for all comers for metastatic colorectal cancer. And we know the median overall survival was more in the less than 12 months range for BRAF. So this was incredibly impactful, and I think should be absolutely practice-changing for anyone who is eligible for this regimen.

I think again, where the practice meets the study is what's kind of important to think about too, how long did patients get FOLFOX, and certainly it adds toxicity to add a BRAF-targeted regimen on top of FOLFOX already. So, one of the other interesting things about the study, though, was that even though it didn't complete treatment, they actually did look at encorafenib/cetuximab alone and in the first line without chemotherapy. And those preliminary results actually looked okay, especially for patients who might not be able to tolerate chemotherapy, which we certainly see in practice. So, overall, definitely more data. And I agree that it's certainly practice-changing.

Dr. Shaalan Beg: And it completely, as you mentioned, changes the outlook for a person who's diagnosed with BRAF-mutated metastatic colon cancer today versus even 7 or 8 years ago.

Dr. Kristen Ciombor: And we're seeing this over and over in other subtypes too, but how you choose to treat the patient up front really matters. So really giving the right regimen up front is the key here.

Dr. Shaalan Beg: And along the same lines, Abstract 3501 wanted to answer the question on whether people with MSI-high metastatic colorectal cancer need double checkpoint inhibitor therapy or is single therapy enough. So this [CheckMate-8HW] study compared nivo plus ipi with nivo alone, nivo monotherapy for MSI-high metastatic colorectal cancer. And we've known that both of these are fairly active regimens, but we also know the chance of immune-related adverse events is significantly higher with combination therapy. So this was a much-needed study for this group of patients. And what were your takeaways here?

Dr. Kristen Ciombor: This, of course, has been really nivo-ipi in the first-line MSI-high metastatic colorectal cancer is now a standard of care. And not everybody is eligible for it, and there could be reasons, toxicity reasons, and other things too. But as we've been seeing for the last couple of years, immunotherapy clearly beats chemo in this space. And now looking at doublet versus single immunotherapy treatment in the first line, I think really nivo-ipi does beat out monotherapy. I will say, however, there is a caveat in that we still haven't seen the nivo-ipi versus nivo in the first line. So what has been presented thus far has been across all lines of therapy, and that does muddy the waters a little bit.

So definitely looking forward and and we've asked this many times and based on the statistical plan and and what not, you know, we just haven't seen that data yet. But I do think it's becoming increasingly important to consider doublet immunotherapy for these patients as long as there are no contraindications. With the again, with the caveat that we have to have these toxicity discussions in the clinic with patients because many patients can tolerate it, you know, this regimen fairly well, but there can be very severe toxicities. So, I think an informed discussion should really be had with each patient before moving forward.

Dr. Shaalan Beg: Yeah, informed decision, making them aware of the potential of real significant toxicities, immune-related toxicities with double therapy. But I am curious in your practice, how often do you see people choosing doublet therapy as frontline?

Dr. Kristen Ciombor: So patients are really savvy, and a lot of times they've heard this data before or have come across it in patient advocacy groups and other things, and it's really nice to be able to have that conversation of the risk versus benefit. So I will say not all of my patients choose doublet, and many of them are still cured with immunotherapy monotherapy. So the big question there is, will we ever understand who actually needs the doublet versus who can still be cured or have very good long-term outcomes with just the single agent? And that has not been answered yet.

Dr. Shaalan Beg: What a great point. So the last abstract I was hoping we could talk about is POD1UM-303 or the INTERAACT2 subgroup analysis and impact of delayed retifanlimab treatment for patients with squamous cell carcinoma of the anal canal. What were your thoughts here?

Dr. Kristen Ciombor: This was a study, actually we saw at ESMO, we saw the primary data at ESMO last year, and this was an update with some exploratory analyses. But this was really an important study because once again, we're looking at immunotherapy in later lines of therapy. That's how we started looking at and investigating immunotherapy, and now we're moving it up and up in the treatment course. So this was a study of carboplatin/paclitaxel plus or minus retifanlimab. Actually it was retifanlimab versus placebo. And it was a positive study, as we heard last year. This actually led to FDA approval of this regimen last month, just before ASCO, and it has now been incorporated in the NCCN guidelines as the preferred first-line option.

So what I thought was important from the additional data presented at ASCO was looking at the different subgroups, it did not appear that patients with liver mets or not had different outcomes. So that was really good to see because sometimes in colon cancer we see that immunotherapy doesn't work as well when patients have liver mets. And interestingly, because we use immunotherapy in anal cancer without any biomarkers, unlike with colon cancer or some of the other tumor types, also the authors looked at PD-L1 status, and it did look like maybe patients did a little bit better if they had higher PD-L1 expression, but patients still could benefit even if they were PD-L1 negative. So that was important, I think, and we will continue to see further data come out from this study. I want to mention also that EA2176 just completed accrual, so that was carbo-taxol plus or minus nivolumab. And so we should be seeing that data sometime soon, which will hopefully also confirm the ongoing role for immunotherapy in the first-line setting for anal cancer.

Dr. Shaalan Beg: That was a fantastic review. Thank you, Dr Ciombor. Thanks for sharing your valuable insights with us today on the ASCO Daily News Podcast.

Dr. Kristen Ciombor: Thanks for having me here.

Dr. Shaalan Beg: And thank you to our listeners for your time today. You will find links to the abstracts discussed today in the transcript of this episode. And if you value the insights that you hear on the podcast, please take a moment to rate, review, and subscribe, wherever you get your podcasts.

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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.