ASCO Guidelines: Duration of Oxaliplatin-Containing Adjuvant Therapy for Stage III Colon Cancer Guideline

TRANSCRIPT

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Hello, and welcome to the ASCO Guidelines Podcast series. My name is Shannon McKernin. And today, I'm interviewing Dr. Nancy Baxter from St. Michael's Hospital in Toronto, senior author on "Duration of Oxaliplatin-Containing Adjuvant Therapy for Stage III Colon Cancer: ASCO Clinical Practice Guideline." Thank you for being here today, Dr. Baxter.

Thanks very much, Shannon, for speaking with me. I'm happy to share our work developing this guideline.

So first, can you give us a general overview of what this guideline covers and the studies which provide the evidence?

Absolutely. So use of adjuvant therapy for patients with stage III colon cancer is common, and it's effective. We know that these patients are at substantial risk of recurrence of their disease and that adjuvant therapy can reduce that risk. But we also know that comes with a cost. The most effective adjuvant therapy is FOLFOX or oxaliplatin-containing chemotherapy regimens. And we know that a really substantial number of people will end up with neurotoxicity, with peripheral sensory neurotoxicity, that can be long lasting and certainly affects their quality of life. So the whole question was whether the duration of oxaliplatin-containing chemotherapeutic regimens could be shortened when they're used for adjuvant therapy, so if we could give three months instead of six months. Because we know that if we give three months of therapy, the risk of neurotoxicity is much lower. So if we had the same effectiveness with the shorter duration, then we could spare patients the negative consequences of the agent given for a longer period of time. So in developing these guidelines, we looked at the results of international group of trials, the six trials from the IDEA collaboration. So these were six randomized trials in various jurisdictions that tried to look at this question, so three months of an oxaliplatin-based chemotherapeutic regimen for adjuvant therapy for stage III cancer versus six months duration of therapy. And so there was a planned analysis to bring all of these data together to develop the evidence base to make this recommendation. So our guideline and our systematic review basically identified this is the key piece of literature to base our recommendations and guidelines on. That's essentially the main study, so the meta-analysis of these six randomized controlled trials that formed the basis of the IDEA collaboration. So the IDEA collaboration studies-- there were six individual randomized trials that formed part of the IDEA collaboration. And they were conducted in Italy, Greece, Japan, North America, through CALGB/SWOG, the UK, Denmark, Spain, Australia, Sweden, and New Zealand, as well as France. So data came from, really, around the world. The median age of people in the studies was 64 years of age. And these people had a really good performance status, so almost all of these patients had an ECOG performance status of 0 or 1. So they were healthy patients that were in the study. And so some patients received CAPOX, and some received FOLFOX. That wasn't part of the randomization scheme. Other than the CALGB/SWOG study, this was up to the discretion of the investigator or patient. In the SWOG/CALGB study, only FOLFOX was given. And the authors planned a prespecified subgroup analysis to look at differences between CAPOX and FOLFOX. There was also a prespecified analysis to look at differences based on stage. What they found when they looked at the results was that, overall, the difference between groups in terms of the three months versus six months was that the hazard ratio between these two was 1.07, meaning a small difference between the groups in terms of recurrence or death between three months and six months overall. But because the prespecified confidence interval, noninferiority interval, for the difference in outcome was 1.12, the 95% confidence interval for the hazard ratio was above this. So it was 1.15, indicating that this prespecified noninferiority margin was exceeded. And so the study did not prove noninferiority of the three-month regimen. So we're left with an inconclusive result. So that's why our guidelines don't have a strong recommendation for the three months, because we can't rule out a small but potentially important difference between the two groups in terms of recurrence or death. Now, interestingly, when they looked at the prespecified subgroup analysis, which was looking at CAPOX versus FOLFOX, a difference was found. So they actually found that for FOLFOX chemotherapy, three months of therapy was inferior to six months of therapy, while for CAPOX, actually, three months and six months were the same. So it met the criteria of noninferiority. So these are kind of two different conclusions based on which type of chemotherapy was used. This was surprising to the investigators and was not expected. And certainly, it was not consistent with the randomized trials that we have comparing these regimens. So we therefore did not make any conclusions in our recommendations about CAPOX versus FOLFOX. But this is certainly something that requires further investigation in the future. In terms of stage, we did not find that there was an interaction between T stage or end stage when you looked at the differences between the three and the six month. And that was the prespecified analysis. But in non-prespecified analysis, which was the higher risk versus lower risk categories, you did find this difference where the patients with high-risk disease had inferior disease-free survival with three months versus six months of therapy, while those at low risk of disease, it seemed quite safe to give three months versus six months. So that's a long story. But essentially, because the high risk versus low risk analysis was not prespecified, there's a limitation to how strong our recommendations can be to have three months of therapy. However, given that the hazard ratio associated with three months versus six months of therapy for this lower risk group was only 1.01, indicating they were the same, and the risk of neuropathy was substantially higher with six months, this has led to us making recommendations that the three months of therapy is adequate for patients with low-risk disease after discussion with patients about the possible pros and cons.

And what are the key recommendations of this guideline?

Well, so the recommendations of this guideline do depend on the pathology, so how high risk the patient is. So based on the evidence from the IDEA collaboration, the researchers found that patients who had a high risk of recurrence-- so had T4 disease or heavily node-positive disease, N2 disease-- the six-month duration of therapy was better than the three-month duration of therapy. These studies and the meta-analysis were designed as noninferiority meta-analyses. But it was clear from the results that the three-month duration was inferior when compared to three months for these high-risk patients. So that seems clear, although we know that those patients will also be at more risk of neuropathy. And so that needs to be discussed with patients, as well. So for the second group, which are patients who are at lower risk of recurrence, what we found was there was less of a clear benefit of six months of therapy. The recommendation was that patients who are in this low-risk category-- so T1, T2, or T3 cancers that are N1, so not heavily node-positive-- clinicians can offer three months versus six months of therapy after having a discussion with their patients about the pros and cons of that. So the clinicians can go ahead and offer that to patients and still be within the common guidelines based on evidence for treatment of stage III colon cancer. So because there's some uncertainty after analysis of the IDEA collaboration, one of the really important recommendations that we make is about this shared decision-making approach. So the third recommendation that we make is that oncologists should discuss these factors with their patients who have stage III resected colon cancer and that the duration of therapy needs to take into account the tumor characteristics-- the surgical resection, the number of lymph nodes examined, the comorbidities, the patient functional status, all of these various things-- and there needs to be a discussion of the potential for benefit and the risk of harm based on the duration of therapy. And oncologists definitely discuss these things with their patients. And this just emphasizes how this is yet another component of the discussion that needs to be included, particularly when speaking with low-risk patients who are at substantial risk of harm from neuropathy and are unlikely to benefit greatly by extending chemotherapy to six months.

So why is this guideline so important? And how will it change practice?

Well, I think, until now, the standard recommendation has been six months of FOLFOX or six months of oxaliplatin-based chemotherapy. And again, there are many patients who have quality of life-affecting neuropathy because of this. So for a substantial proportion of patients who present to us with stage III cancer-- so those that are low risk-- I think this provides some options to them. So they can opt for a shorter duration of chemotherapy with a lower risk of toxicity. This saves time. This saves cost to the patient and to the system and potentially improves their quality of life without a great impact on outcome in terms of disease recurrence. So that's a substantial number, a substantial proportion of our patients, who can be treated in this way. So I think that this is a real benefit. Again, oncologists need to have a conversation with their patients about the pros and cons. But this is an option for their patients, whereas from an evidence-based perspective, it wasn't before the publication of the IDEA collaboration.

Finally, how will these guideline recommendations affect patients?

So for patients who have heavily node-positive disease-- so high-risk patients with T4 or N2 disease-- it's not going to affect care. So the expectation would be those patients would be treated with six months of therapy, similar to previous recommendations. So this will be for people who are at lower risk of disease recurrence, so patients with T1 to 3 tumors that are N1 positive, so not heavily node positive. So these patients will have the opportunity to opt for a shorter duration of therapy. So that's a major benefit to patients. Again, it's important that there's a discussion and that patients understand the pros and cons. But this is now an option for them, which is excellent.

Thank you to all of our listeners for tuning into the ASCO Guidelines Podcast series. To read the full guideline, please go to www.asco.org/gastrointestinal-cancer-guidelines. And if you've enjoyed what you've heard today, please rate and review the podcast and refer the show to a colleague.