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An interview with Dr. Van Morris from The University of Texas MD Anderson Cancer Center in Houston, TX and Dr. Cathy Eng from Vanderbilt-Ingram Cancer Center in Nashville, TN, co-chairs on "Treatment of Metastatic Colorectal Cancer: ASCO Guideline." Dr. Morris and Dr. Eng review the evidence-based recommendations from the guideline, focusing on areas of uncertainty in the treatment of metastatic colorectal cancer, and highlighting the importance of multidisciplinary collaboration and shared decision-making between patients and clinicians. Read the full guideline at www.asco.org/gastrointestinal-cancer-guidelines.

TRANSCRIPT

Brittany Harvey: Hello, and welcome to the ASCO Guidelines Podcast series, brought to you by the ASCO Podcast Network; a collection of nine programs covering a range of educational and scientific content and offering enriching insight into the world of cancer care. You can find all the shows, including this one, at: asco.org/podcasts.

My name is Brittany Harvey, and today I'm interviewing Dr. Van Morris, from The University of Texas MD Anderson Cancer Center in Houston, Texas, and Dr. Cathy Eng from Vanderbilt-Ingram Cancer Center in Nashville, Tennessee - co-chairs on, 'Treatment of Metastatic Colorectal Cancer, ASCO Guideline.'

Thank you for being here, Dr. Morris, and Dr. Eng.

Dr. Cathy Eng: Thank you.

Dr. Van Morris: Thank you.

Brittany Harvey: First. I'd like to note that ASCO takes great care in the development of its guidelines and ensuring that the ASCO Conflict of Interest policy is followed for each guideline. The full Conflict of Interest information for this guideline panel is available online with the publication of the guideline in the Journal of Clinical Oncology.

Dr. Morris, do you have any relevant disclosures that are directly related to the guideline topic?

Dr. Van Morris: Not personally, but I do have research support to my institution from Pfizer and Bristol Myers Squibb who have products that I'll be discussing on this podcast.

Brittany Harvey: Thank you, Dr. Morris. And Dr. Eng, do you have any relevant disclosures that are directly related to this guideline topic?

Dr. Cathy Eng: Also, not personally associated with any honorarium specific to this topic.

Brittany Harvey: Great. Thank you both. So then, let's talk about the content of this guideline. So first, Dr. Morris, can you provide an overview of the scope of this guideline?

Dr. Van Morris: Sure. So colorectal cancer is the second-leading cause of cancer-related death in the United States. And especially in the time of the recent COVID-19 pandemic with people less likely to go for screening colonoscopies, there's great concern that more and more patients will be presenting at the time of their initial diagnosis with later-stage, more advanced colorectal cancer. So with that said, research is moving very quickly for the benefit of patients with colorectal cancer, and we were interested in assembling a multidisciplinary team that consisted of medical oncologists, surgical oncologists, radiation oncologists, pathologists, and radiologists as well, to help us make guidelines that really summarize the most relevant up-to-date practices, based on rigorous literature review for treatment recommendations for advanced metastatic colorectal cancer.

Brittany Harvey: Great. And then as you just mentioned, this guideline provides recommendations, and a lot of those focus on areas of uncertainty in the treatment of metastatic colorectal cancer. And I'd like to review those key recommendations that you mentioned for our listeners.

So, Dr. Eng, starting with - for patients with previously untreated, initially unresectable metastatic colorectal cancer, who are candidates for chemotherapy plus bevacizumab, is doublet or triplet cytotoxic chemotherapy recommended?

Dr. Cathy Eng: For treatment-naive patients, bevacizumab has been approved, and we do agree that it's a very reasonable treatment option with doublet or triplet therapy for our patient population. Obviously, these are guidelines, and it's extremely important to keep in mind that as a provider, you need to discuss the potential side effects with the patient. With bevacizumab, you know, standard concerns must be discussed with the patient, especially in regards to wound healing, if they've had recent surgery or any potential risk factors for a recent cardiac event from a recent thrombosis. So, those things obviously, would preclude the patient from initiating treatment with bevacizumab. But currently, doublet therapy or triplet therapy could be a potential option for patients.

Brittany Harvey: Great. And yes, as you mentioned, shared decision-making is paramount to these decisions.

So then following that recommendation, Dr. Morris, which patients should be offered pembrolizumab in the first-line setting?

Dr. Van Morris: Yeah. So, I think that this represents really one of the exciting advances in the treatment of metastatic colorectal cancer over the past several years. We have great data now that suggests for patients with microsatellite instability-high metastatic colorectal cancer, especially who have not had any prior treatment, we would recommend use of immune checkpoint blockade therapies, really coming from the seminal KEYNOTE-177 trial. This was a phase III international trial that looked at patients with advanced unresectable or metastatic colorectal cancer. And patients were either randomized to pembrolizumab monotherapy, or cytotoxic chemotherapy with FOLFOX, with or without bevacizumab. And this trial did meet its primary endpoint and showed an improvement in progression-free survival, with use of pembrolizumab as a single agent relative to cytotoxic chemotherapy. And based on this trial and the clear benefit that we see in patients with pembrolizumab, the FDA has approved this as an option for patients with MSI-high untreated metastatic colorectal cancer.

There are other trials which have looked at use of immunotherapy; the CheckMate 142 trial looked at combination PD-1 CTLA-4 therapy as a single-arm study. And, you know, there's another trial, the CheckMate 8HW, which is looking at one versus two immunotherapy agents in this setting as well. But really, as it stands for now, patients with MSI-high untreated metastatic colorectal cancer are the ones who benefit from the use of immunotherapy.

One of the questions that we often get in talking with other clinical oncologists is the FDA approval for pembrolizumab in any cancer type for a TMB, tumor mutation burden, greater than 10. And, we talked about this with our panel in this context, and we don't see that patients with microsatellite-stable metastatic colorectal cancer, who have a tumor mutation burden over 10 benefit from use of immunotherapy. There is one exception to this for patients who harbor pathogenic POLE or POLD1 mutations, these patients oftentimes do experience sustained clinical benefit with immunotherapy. But in general, patients with microsatellite-stable metastatic colorectal cancer, who don't have POLE/POLD1 mutations, we don't favor use of immunotherapy in that context at this point in time.

Brittany Harvey: Great. Thank you for reviewing that recommendation and the data behind who benefits and who doesn't benefit from immunotherapy in this setting.

So then following that, the next question that this guideline addressed is for treatment-naive RAS-wild type metastatic colorectal cancer. So, for these patients, Dr. Eng, is anti-EGFR therapy recommended for patients with right or left sided primary tumors?

Dr. Cathy Eng: That is such an important question, and thank you for asking this. We know based upon pivotal data from CALGB/SWOG 80405, that right-sided tumors treatment-naive, even if they're RAS-wild type, these patients should not receive anti-EGFR therapy. But also, we've learned from 80405, FIRE-3, and PEAK, which was a phase two study, that there appeared to be some benefit versus anti-VEGF therapy for left-sided tumors based upon studies that have been conducted.

So, at this year's ASCO, actually, the PARADIGM trial was specifically a phase III trial, more focused on left-sided tumors. It was amended twice before it decided to focus on the left-sided patient population. And it was a phase III study where patients were randomized to FOLFOX plus panitumumab versus FOLFOX and bevacizumab. And the primary endpoint was overall survival. And we added this data to our guidelines. This data just came out, hot off the presses in June, at this year's ASCO. And the primary endpoint was fulfilled. And basically, it prospectively demonstrated that the data from the other three trials, based upon a pooled analysis, suggested left-sided tumors fare better with anti-EGFR therapy. And in fact, the PARADIGM trial basically validated those findings. Obviously, the PARADIGM trial just recently presented, we have not seen the final publication, we do not know much about the maintenance setting, but specifically, when thinking about anti-EGFR therapy, it is very reasonable to consider it in a left-sided tumor, all RAS-wild type patient population.

I would like to mention though, and we do highlight this also in the guidelines, which is critically important, is that there was another study, which is a phase III trial called, TRIPLETE, that was presented as well, looking at FOLFOXIRI plus panitumumab versus basically, standard treatment. And what it noted is that there is no additional benefit for FOLFOXIRI plus panitumumab in left-sided tumors in regards to response or progression-free survival, there was no additional benefit. So, FOLFOX plus panitumumab seems very reasonable, FOLFOXIRI plus panitumumab is not necessarily needed in left-sided tumors.

Brittany Harvey: Great. Thank you for that explanation, and also for the work of the panel to rapidly include this new information recently presented at ASCO.

So then following those recommendations, Dr. Morris, what recommendation did the panel make for patients with previously-treated metastatic colorectal cancer with a BRAF V600E mutation?

Dr. Van Morris: Yeah. So, this recommendation was made essentially based on one randomized phase III clinical trial, which reported out about three years ago now, the BEACON trial. This is looking at patients with BRAF V600E mutated metastatic colorectal cancer, which we know accounts for probably eight to 10% of all patients with advanced colorectal cancer, and when found, really harbors a poor prognosis relative to BRAF-wild type counterparts.

So, the BEACON trial was a trial that looked at patients with previously-treated metastatic colorectal cancer, who have BRAF mutations, either kind of standard of care cytotoxic chemotherapy, or a BRAF/EGFR combination with encorafenib and cetuximab or alternatively, a BRAF/EGFR/MEK combination. That trial showed that improvement in survival outcomes with a BRAF/EGFR-targeted approach, as well as the BRAF/MEK/EGFR. However, because there was no difference in survival with the addition of the MEK inhibitor, the FDA subsequently approved encorafenib and cetuximab as the recommended treatment for patients with BRAF V600E previously-treated metastatic colorectal cancer. Because the MEK combination with binimetinib was not recommended by the FDA, you know, we did not include that analysis in our guidelines for ASCO. But as it stands right now, we do strongly encourage all clinicians to check for their BRAF V600E mutation status in their patients with metastatic colorectal cancer, with the goal of getting them to a targeted therapy approach over their treatment course.

Brittany Harvey: Great. Thank you for providing that information.

So, following that, Dr. Eng, what are the recommendations for patients with colorectal peritoneal metastases?

Dr. Cathy Eng: The current recommendations for colorectal cancer with peritoneal disease, really, there's no strong evidence to support the role of heated intraperitoneal chemotherapy. We now know based upon the literature from one of the largest studies to date, the PRODIGE data, demonstrating that there may be some potential benefit from cytoreductive surgery for the patients in regards to overall survival. But these patients are at high risk for bowel obstruction, potentially for perforation, and obviously, quality of life is an issue. So, these patients should always be discussed in a multidisciplinary tumor board whenever possible, and hopefully, to meet with a surgeon that is more experienced, specifically, in treating peritoneal disease, because these patients do require a lot of multidisciplinary care and discussion. So currently, based upon the existing data, we don't recommend heated intraperitoneal chemotherapy, but there may be a role for cytoreductive surgery.

Brittany Harvey: Thank you, Dr. Eng for going over those recommendations.

So then following that, Dr. Morris, for patients with unresectable liver-limited metastatic colorectal cancer, which liver-directed therapies are recommended?

Dr. Van Morris: So, this is I think a really good question and one that just like the prior question with regards to peritoneal surgery, is one that we felt was a challenging one, but a common one that we wanted to address. And specifically, I think this is an example of where level of evidence comes into the strength of recommendation.

So, for patients with unresectable liver-limited metastatic colorectal cancer, we looked at the questions of, "What is the role of SBRT - stereotactic body radiotherapy, and what is the role of SIRT, which is selective internal radiotherapy?" And for both of these, we felt that the level of evidence was weak, and I think that it's very important to make note of that in assessing the recommendations.

But to start with, for SBRT, we looked at one meta-analysis for patients with oligometastatic colorectal cancer, and also analyzed 18 non-randomized control trials in this setting. Most of the patients in these studies had one to five liver metastases, with the majority having one or two liver metastases. From the meta-analysis, we saw kind of a one-year local control rate of around 67%, a two-year control rate of 59%. So, based on those and recognizing the limitations of non-randomized trials and making recommendations, the panel did feel that it was reasonable to consider use of SBRT for oligometastatic colorectal cancer. The SABR-COMET trial is one that had looked at the role of radiotherapy for treatment of oligometastatic colorectal cancer, and I just want to make the point as well, that we did not include that in our analysis or recommendations at this point in time, because this really didn't include a lot of patients with colorectal cancer that we felt warranted inclusion.

Now, with regards to SIRT, we looked at kind of one meta-analysis and three randomized control trials for patients with mostly liver-limited metastatic colorectal cancer. All patients had liver disease, but there were about 40% of the patients we looked at in the meta-analysis, had extra hepatic disease as well. In the frontline setting, there really was no difference in progression-free survival or overall survival with the use of SIRT. And more recently, we've seen in a second-line trial, it was called the EPOCH trial, reported several years ago, this looked at patients with previously-treated metastatic colorectal cancer in the second-line setting. Patients were randomized to either chemotherapy with, or without transarterial radioembolization with Y90.

While there was an improvement in overall response rate, there was no meaningful improvement in overall survival with the use of SIRT. But there were significant increases in grade 3 or grade 4 toxicities when SIRT was added to chemotherapy. So, kind of given this, we didn't feel at this point in time that SIRT should be recommended for patients with metastatic colorectal cancer. Although, again, I do want to highlight that really these discussions should be happening at high-volume centers, kind of with a multidisciplinary group of clinicians.

Brittany Harvey: Definitely. And thank you for highlighting that multidisciplinary collaboration.

And the last section of recommendations, Dr. Eng, what is recommended for patients with metastatic colorectal cancer, and potentially-curable oligometastatic liver metastases?

Dr. Cathy Eng: So, another controversial topic. And once again, this is why we decided to include this as part of the guidelines, because this is a common scenario where patients are potentially curable, following liver resection for oligometastatic disease. We cannot highlight enough the importance of multidisciplinary discussion. Prior data has not been strong regarding specific guidelines following liver resection. We do recommend that based upon the existing data, there is no level one evidence to say, you should go one way or another following metastatic resection, and whether or not adjuvant therapy is warranted in that setting. But we do recommend multidisciplinary management and engagement and discussion. So, although it's not definitive, it basically suggests that there is a role for resection. It does provide improved five year survival relative to systemic chemotherapy, if the patient is potentially resectable, but does require multidisciplinary discussion. And it is a shared decision-making process.

Brittany Harvey: Great. Thank you. And I appreciate you highlighting the importance of shared decision-making throughout this guideline.

So then, Dr. Morris, what is the importance of this guideline in your opinion, and how will it impact clinical practice?

Dr. Van Morris: Yeah. So, I think that we understand that management of metastatic colorectal cancer is extremely complex given the various molecular annotations and the multimodality therapies which are possible for our patients. So, we tried to limit the guidelines here to include what we feel are the most recent updates, but also kind of the most clinically-relevant multidisciplinary questions that get asked for treatment of metastatic colorectal cancer. We also recognize that things are changing quickly. And for example, we didn't decide to include at this point in time, management of HER2 neu amplified metastatic colorectal cancer, although we are seeing more and more data coming out, suggesting targeted therapies. So, I think it's important for clinicians to realize that these are guidelines which are ever-changing, given the updates with new therapies available for our patients.

And the other thing I think that's very good about these guidelines is that, even though we may be making recommendations about controversial topics in the management of metastatic colorectal cancer - specifically, I think the use of HIPEC with cytoreductive surgery, locally-directed therapies to the liver, and the role of perioperative chemotherapy and metastasectomy - I think it's important for oncologists to realize that these recommendations come with varying strengths of level of evidence and that we as oncologists should be considering the level of evidence that's out there when making recommendations that affect our patients as well. So, we really wanted to support these guidelines and recommendations and empower clinicians to know and understand the quality of evidence that exists in the management of patients with metastatic colorectal cancer.

Brittany Harvey: Excellent. And yes, those are key points on the level of evidence and the strength of recommendations throughout the guideline.

And then finally, Dr. Eng, you've talked a bit about shared decision-making and the importance of this guideline for patients. So, how will these guideline recommendations affect patients with metastatic colorectal cancer?

Dr. Cathy Eng: The reason that we created these guidelines is to help patients, their caregivers, and providers, learn of the most recent developments in colorectal cancer, and the best approach based upon the information that we have personally reviewed with our multidisciplinary team of faculty members that participated in this exercise. We really just want to make sure that patients do get optimal care. And we hope that these guidelines also will help provide a foundation for some of the clinical trials that may be under development, or for other clinical trials that are being considered. So, we really just want to provide the most up-to-date information to all individuals that are interested in colorectal cancer so we can help guide their care better.

Brittany Harvey: So, I want to thank you both so much for your work on these guidelines, and all of the time it's spent developing these recommendations, and thank you for your time today, Dr. Morris, and Dr. Eng.

Dr. Van Morris: Thank you.

Brittany Harvey: And thank you to all of our listeners for tuning into the ASCO Guidelines Podcast series. To read the full guideline, go to: www.asco.org/gastrointestinal-cancer-guidelines.

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