Adjuvant Therapy for Stage II Colon Cancer Guideline Update

An interview with Dr. Nancy Baxter from the University of Melbourne in Melbourne, Australia, and Dr. Jeffrey Meyerhardt from Dana-Farber Cancer Institute in Boston, MA, co-chairs on "Adjuvant Therapy for Stage II Colon Cancer: ASCO Guideline Update." This guideline updates recommendations for adjuvant therapy for patients with resected stage II colon cancer. Read the full guideline at www.asco.org/gastrointestinal-cancer-guidelines.

TRANSCRIPT

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ANNOUNCER: 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. The mention of any product, service, organization, activity, or therapy should not be construed as an ASCO endorsement.

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. Nancy Baxter from the University of Melbourne in Melbourne, Australia, and Dr. Jeffrey Meyerhardt from the Dana-Farber Cancer Institute in Boston, Massachusetts, co-chairs on adjuvant therapy for stage II colon cancer ASCO guideline update. Thank you for being here, Dr. Baxter and Dr. Meyerhardt.

NANCY BAXTER: Thank you for having us.

JEFFREY MEYERHARDT: Thanks.

BRITTANY HARVEY: First, I'd like to note that ASCO takes great care in the development of its guidelines in 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. Baxter, do you have any relevant disclosures that are directly related to this guideline topic?

NANCY BAXTER: I don't, Brittany.

BRITTANY HARVEY: Thank you. And Dr. Meyerhardt, do you have any relevant disclosures that are directly related to this guideline topic?

JEFFREY MEYERHARDT: I don't, either. Thank you.

BRITTANY HARVEY: Thank you, both. And getting into the content of this guideline, what prompted this guideline update, and what is the scope of this guideline?

NANCY BAXTER: Well, it's been since 2004 that we've had a guideline that gives us advice about stage II colon cancer and the use of adjuvant therapy in this group of patients. And it's one where clinicians often have a lot of challenges in helping patients make decisions about what's best for them in terms of long-term survival from colon cancer. There have been changes in guidelines for stage III colon cancer. And so we thought it was timely to reevaluate our best practice recommendations for stage II colon cancer patients.

JEFFREY MEYERHARDT: Yeah, I agree, Dr. Baxter. I think that this is one of the most challenging conversations that oncologists have with patients. Should they get chemotherapy? What type of chemotherapy? And as you know, there are a variety of higher risk features, of which we're able to sort of tease out a little better relatively, in terms of thinking about someone's stage II disease and trying to bring all that data together and provide some framework in the conversation for clinicians to have with patients.

BRITTANY HARVEY: Great, thank you both for that background information. So then this guideline covers four clinical questions. And I'd like to review the recommendations for each question. So Dr. Baxter, starting with question 1, what does the guideline recommend for patients with resected stage II colon cancer regarding the benefit of fluoropyrimidine-based adjuvant chemotherapy versus surgery alone?

NANCY BAXTER: So overall, what we did was we looked at the risk that individual patients with stage II colon cancer have. So for patients that are at low risk of recurrence-- and so those are patients with stage IIA or T3 tumors that have at least 12 sample lymph nodes in the surgical specimen and don't have any high-risk features, and I'll go over those with the later recommendations-- these patients do not need adjuvant chemotherapy.

It should not be routinely offered to them because the harms may outweigh the benefits. And so the evidence of that, although the quality of the evidence was relatively low, there is quite a bit of evidence that, really, the benefits do not outweigh the risks in this particular group.

That is different for patients that are at higher risk, though, within the stage II group. And so those are the patients with stage IIB or stage IIC colon cancer. So those are T4 lesions that either penetrate through the visceral peritoneum or invade surrounding organs.

And in those patients, adjuvant chemotherapy may have more benefit. And so a discussion of the potential benefits and risks of harms associated with chemotherapy should be had with patients. And those are patients that should be offered adjuvant chemotherapy for their disease.

Now, there's a group of patients with high-risk features-- so not the stage IIB or stage IIC-- but there's a group of patients within stage IIA. So these are patients that are T3 patients where there are high-risk features. And chemotherapy may be offered to these patients, based on their risk features.

So I'll go over a little bit about what the high-risk features are that might make patients included in this group. So that is sampling of fewer than 12 lymph nodes in the surgical specimen, perineural or lymphatic invasion, poor or undifferentiated tumor grade, intestinal obstruction, tumor perforation, and grade BD3 tumor budding. That's more than, or equal to, 10 buds in the tumor.

And so that's because these patients are at higher risk of recurrence, and the chemotherapy may be more beneficial in these patients because they have a higher baseline risk of recurrence. There were a few risk factors that it was really challenging to make any decision on.

And that was specifically circulating DNA. We know that that's an area of great interest, but there really was not enough evidence of the predictive value of ctDNA when you're looking at adjuvant chemotherapy in this group to make a recommendation. We'd expect future versions of this guideline to have some recommendations about that.

We do know that there is controversy around the timing of chemotherapy. So we didn't include reports on this for the guideline because we didn't have enough related to stage II colon cancer and the role of adjuvant therapy. But the trials have generally started patients on chemotherapy within six to seven weeks of surgery.

And finally, all of this needs to be a part of shared decision-making. So particularly for patients at higher risk-- so stage 2A at higher risk-- it's important that this is discussed-- the risks and benefits of chemotherapy, and the possible benefits with respect to the risk of recurrence for these patients-- is discussed as part of the shared decision-making process to come to an ultimate decision about the use of chemotherapy.

BRITTANY HARVEY: Understood. Thanks for detailing those recommendations stratified by risk and identifying what those high-risk features are. So then, additionally, Dr. Meyerhardt, is there a benefit of fluoropyrimidine-based adjuvant chemotherapy for patients with tumors that exhibit mismatch repair deficiency or microsatellite instability or patients with proficient mismatch repair, or microsatellite-stable, tumors?

JEFFREY MEYERHARDT: Yeah, so this was a specific question that we also looked at. What we know is about 15% of stage II colon cancers have evidence of mismatch repair or microsatellite insufficiency. And data that was realized now several decades ago on several different papers-- one larger one published in The New England Journal by Dan Sargent-- showed that patients who have stage II disease who receive a fluoropyrimidine only seem to not benefit if they have microsat instability.

And there was actually some evidence that they may actually have harm, or have a worse outcome. So it is not a routine recommendation to use a fluoropyrimidine-only treatment regimen in patients who have MSI-high or deficiency of mismatch repair in stage II disease.

However, there are some qualifying statements that we reviewed and were important to think about in patients. So what we know is, again, some of those patients will have some high-risk features and particularly T4 tumors or some other high-risk features, except for poor differentiation, that the use of oxaliplatin may actually be a consideration in those patients. And that's basically from indirect evidence of a disease-free survival benefit with the addition of oxaliplatin in the population of patients with stage II disease that were included in the MOSAIC trial, one of the original trials that looked at the addition of oxaliplatin to a fluoropyrimidine as adjuvant therapy for colon cancer.

We specifically carved out poor differentiate is not considered a high-risk prognostic feature in those patients. And so poorly differentiated tumors alone should not be a part of the decision in offering adjuvant therapy with a fluoropyrimidine or fluoropyrimidine-oxaliplatin for MSI-high or deficient mismatch repair protein tumors. And the other patients who have either proficient mismatch repair proteins or microsatellite instability are actually including the other parts of the guideline, so what Dr. Baxter just talked about and some of the other questions that we tackled that you'll be going to next.

BRITTANY HARVEY: Great. Thank you for covering those recommendations for that particular patient population. So then, Dr. Baxter, if adjuvant therapy is recommended, is there a benefit to adding oxaliplatin to fluoropyrimidine-based chemotherapy?

NANCY BAXTER: Well, this is obviously a question that oncologists will face when they're deciding to give adjuvant chemotherapy to high-risk stage II colon cancers or people with T4 stage IIB or C colon cancers. And you know, here's where it's challenging to make recommendations. Because we don't have a lot of evidence for this specific group. And this is why clinicians have such a challenge making recommendations for these patients.

Because actually, there's insufficient evidence to routinely recommend the addition of oxaliplatin, meaning that we have to base our decisions on the best evidence that we have. And the best evidence we have, as we've talked about, is the MOSAIC trial. And so in the MOSAIC trial, a time to recurrence was longer with oxaliplatin-based adjuvant chemotherapy.

And so it may be for some patients that the addition of oxaliplatin makes sense in terms of improving their overall outcome. And again, it needs to be a shared decision-making approach with the discussion of the potential benefits and risks of harms of the addition of oxaliplatin to fluoropyrimidine-based chemotherapy, so again, discussions between the oncologist and the patient.

But that is with the exception of patients who are MSI-high. So those patients need oxaliplatin. If they're going to get chemotherapy, they shouldn't have 5FU-based chemotherapy alone, as we've just discussed.

BRITTANY HARVEY: Great. And definitely, that shared decision-making is key. And I appreciate you reviewing the evidence behind these recommendations, as well. So then, the last clinical question addressed in this guideline, Dr. Meyerhardt, if adjuvant oxaliplatin-containing chemotherapy is considered, are outcomes affected by reducing the treatment duration from six months to three months?

JEFFREY MEYERHARDT: Sure. So this was the last clinical question that the committee considered. And it is based on the IDEA collaboration. So the IDEA collaboration was the International Duration Evaluation of Adjuvant Chemotherapy. It was six trials that were done internationally-- one in the United States, one in Japan, and four in Europe-- that included patients both with stage II and stage III colon cancer. They receive three versus six months of therapy.

Each of the trials had different chemotherapy choices in the sense that the United States trial, FOLFOX was the only choice that could be offered to patients, where in all the other trials, it was a physician and patient choice regarding the use of FOLFOX or capecitabine and oxaliplatin. And that, as people who know the data, is relevant to some of the discussion.

And so the goal of the collaboration was to look at if we can give patients three months of therapy and not compromise outcome. And the main reason for that is we know that the peripheral neuropathy that's cumulative with oxaliplatin increases with more months of treatment. So patients who only receive three months of oxaliplatin have less likelihood of more significant cumulative neuropathy and will have less impact on function by receiving less oxaliplatin overall.

Four of the trials included patients with stage II disease. And those trials, again, pooled their data and looked at the duration question in terms of for stage II patients. Those patients had high-risk disease, some high-risk feature, as discussed earlier.

And what was shown is that for the patients, overall, there was not clear evidence of noninferiority with three versus six months. But when you looked at the patients who received capecitabine and oxaliplatin, the absolute five-year disease-free survival was 81.7% versus 82% for three versus six months of CAPOX, so essentially the same, with a hazard ratio of 1.02, and the confidence interval spanned across 1. And so those really didn't look like there was any compromise in outcome for patients to receive CAPOX for three months versus six months.

For those patients who received FOLFOX, three months of chemotherapy led to a five-year disease-free survival of 79.2% versus 86.5% if you received six months of FOLFOX with a hazard ratio 1.41. So again, those data would suggest that if one was to choose FOLFOX, giving six months of therapy for high-risk stage II patients may be preferable to not potentially compromise some benefit in terms of disease-free survival.

So again, the overall conclusion was it's a discussion with a patient regarding choice of therapy, whether receiving capecitabine, oxaliplatin or FOLFOX and then, based on that, consideration of the duration where we were most comfortable saying that three months of capecitabine, oxaliplatin is sufficient for high-risk patients when appropriate discussion between the clinician and the patient.

BRITTANY HARVEY: Great. Thank you for explaining the nuance of that trial and your recommendation. So finally, to wrap us up, in your view, how does this guideline impact both clinicians and patients?

JEFFREY MEYERHARDT: Yeah, so again, the last time ASCO had addressed guidelines for stage II patients was over 15 years ago. And there are more data. It was really early in the days of understanding the incorporation of oxaliplatin. There was no data versus the three versus six months. And there were less analyses trying to look at some of those particular high-risk features.

So these are all important considerations in those discussions with stage II patients. And the importance of the guidelines are really to provide that framework on the various things you think about when you have a stage II patient and how to have those shared decision-making discussions with the patient.

Again, it's not, probably, appropriate for all patients to receive adjuvant therapy, particularly lower risk. And even for higher risk patients, it is weighing the plus or minuses of the potential toxicities with what we know potentially are benefits.

NANCY BAXTER: Yeah, I think that's very true. And I think, as anyone who treats colon cancer, or stage II colon cancer patients, is aware, this is not a homogeneous population. So in terms of the outcomes, there are people that do extremely well with surgery alone and people who, unfortunately, recur even after chemotherapy and surgery. And the future needs to focus on being able to differentiate those patients most likely to benefit from chemotherapy from those that are not likely to benefit.

What we found in reviewing the evidence is we've moved forward from 2004, but we still have a long way to go. So I really hope when the next guideline is written that we're much closer to being able to identify those patients who would most benefit from chemotherapy in this group.

Because we know there are patients who benefit from chemotherapy in this group. It's just we're still not perfect at identifying those people. So again, these conversations with patients are so important to talk about the limits of our knowledge, which I think is another important thing of this guideline is establishing what the limits of our knowledge are.

But I think there are patients that you can confidently not give chemotherapy to. And that's very reassuring, both to clinician and to patients. And then this guideline kind of outlines the limits of our knowledge. And that's also important for clinicians and patients to understand.

BRITTANY HARVEY: Definitely. I appreciate you both highlighting the importance of shared decision-making throughout this conversation that we've had. So I want to thank you so much for your work on this important guideline update and for taking the time to speak with me today, Dr. Baxter and Dr. Meyerhardt.

NANCY BAXTER: Thank you very much.

JEFFREY MEYERHARDT: Thank you.

BRITTANY HARVEY: And thank you to all of our listeners for tuning in to the ASCO Guidelines podcast series. To read the full guideline, go to www.asco.org/gastrointestinal cancer guidelines. You can also find many of our guidelines and interactive resources in the free ASCO Guidelines app, available in iTunes or the Google Play store. If you've enjoyed what you've heard today, please rate and review the podcast, and be sure to subscribe so you never miss an episode.

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