The Role of TTF in Lung Cancer Treatment

Drs. Vamsi Velcheti and Jack West discuss ADAURA, KEYNOTE-671, and KEYNOTE-789 trials in NSCLC and the first pivotal study of sunvozertinib for the treatment of NSCLC with EGFR exon 20 insertion mutations.

TRANSCRIPT

Dr. Vamsi Velcheti: Hello, I'm Dr. Vamsi Velcheti, your guest host for the ASCO Daily News Podcast. I'm a professor of medicine and director of thoracic medical oncology at the Perlmutter Cancer Center at NYU Langone Health. My guest today is Dr. Jack West, a thoracic oncologist and associate professor in medical oncology at City of Hope Comprehensive Cancer Center. Today, we'll be discussing practice-changing studies and other key advances in lung cancer that were featured at the 2023 ASCO Annual Meeting.

Our full disclosures are available in the transcript of this episode and disclosures of all guests on the ASCO Daily News podcast are available at asco.org/DNpod.

Jack, there was a lot of exciting new data that emerged from the ASCO Annual Meeting, and it's great to have you back on our podcast today to talk about all the key updates in lung cancer.

Dr. Jack West: Absolutely. Thanks so much. It's always a high-energy meeting, and there was a lot to talk about in the lung cancer sessions this year for sure.

Dr. Vamsi Velcheti: Let's begin with LBA3, the ADAURA trial. This was presented in the Plenary Session at ASCO; we've heard previously the DFS updates from previous meetings, and overall survival updates were presented at the ASCO 2023 Annual Meeting. So, Jack, what was the highlight of the presentation for you? And could you put things in context for us? We have known about the DFS data for a while now. What gets you so excited about this study?

Dr. Jack West: Well, we've actually been focused on this trial for literally 3 years, since Dr. Herbst presented it at another Plenary presentation back in the ASCO Meeting in 2020 when we saw tremendous differences in the DFS data. Again, this was a trial of patients with resected stage 1b to 3a EGFR mutation-positive non-small cell lung cancer. Nearly 700 patients were randomized to after-surgery, and for many, but not all, patients undergoing chemotherapy, it wasn't mandated. But after that, they were randomized to get adjuvant, placebo, or osimertinib for up to 3 years. And we saw huge differences in the disease-free survival from the first presentation, with a hazard ratio in the range of 0.2.

We have notably seen significant improvements in disease-free survival before with other EGFR TKIs for this population after surgery, but nothing in this range. And it's also notable that in the various other trials of other EGFR inhibitors in the postoperative setting, we've seen a DFS benefit, but that didn't translate to an improvement in overall survival. So, seeing a press release that this was associated with a significant and, in fact, highly significant by report, improvement in overall survival, as well as DFS, was really notable.

What's also, I think, particularly important as a focus of this is that in the later presentations of this work, with longer follow-up last year, we saw that the DFS curves showed a drop in the DFS starting after these patients had completed 3 years of treatment. So, really suggesting that at least some, if not many or most of these patients who had been on adjuvant osimertinib were subject to a higher risk of relapse once they completed that. So, again, making the endpoint of overall survival particularly important. It's always been to me the endpoint we should care about most in a curative setting. Although the DFS was the primary endpoint of the study and it was powered and built around specifically focusing on the DFS difference, so overall survival was reassuring, I think, when we actually saw it, but not what the trial was centered around.

And what we saw was a very dramatic improvement in overall survival with a hazard ratio of 0.49. That was essentially the same for the patients with stage 2 to 3a disease, as well as the broader population with stage 1b to 3a disease. When we look at the absolute numbers for overall survival at 5 years, there was an improvement from 73% to 85% with osimertinib, and in the population from 1b to 3a, an improvement from 78% to 88%. So, many things to comment on here. Really remarkable to see an 88% 5-year survival in the osimertinib arm that includes patients with stage 3a disease.

I would say that there's still some controversy, some questions about this, and it really centers around a few things. One is, like many global trials, this one enrolled patients from many places that did not have the same standard of care staging that we follow in the U.S. There wasn't any specification or mandate for PET scans, which would be very routine in the U.S. And brain MRIs were not mandated either. And so there were almost certainly some patients with more advanced disease that was not detected that would be a big advantage for the osimertinib arm, but really not characterized. And also, the crossover was made possible to osimertinib starting in April of 2020, but only 38.5% of the patients on the control arm actually received osimertinib at the time of relapse. And even though many of the other patients who had a relapse did get another EGFR inhibitor, I don't think there's much question that osimertinib is the preferred and optimal EGFR TKI.

And so there were a couple of important factors kind of going for this trial. One is the long, long, long duration of treatment at 3 years, though with a drop-off, I think some questions about whether even that is enough, and we might be tempted to treat beyond 3 years. And then how much did the inability of most of the patients on the control arm to get osimertinib later contribute? My personal view is that it is a troubling aspect of this trial. But also so many other trials that they're run globally in places where we arguably perpetuate these disparities by running these trials that, in part, magnify the differences between the two arms because some patients just will not have access to what is our best standard of care in the U.S., or many other parts of the world, but weren't necessarily available to many of the patients on the control arm where it was conducted. So, I think that's always a concern. It's definitely an issue of this trial, but I would not say it's unique to this one.

Dr. Vamsi Velcheti: Very good points, Jack, and I completely agree with you. I think those certainly are concerns. But on the other hand, this is a pragmatic trial and that's the real-world scenario in terms of access issues, in terms of osimertinib globally, correct, in the stage 4 setting, even though we all agree that osimertinib is the best option for patients with metastatic EGFR-mutated lung cancer, I think that's obviously a reflection of global access issues and global disparities and changes in standard of care in terms of workup as well. So, it's somewhat of a pragmatic trial in some ways and I completely agree with you, I think that may have potentially had some impact on the overall survival.

Dr. Jack West: Well, I would clarify that I don't think that this really highly significant difference in overall survival is undermined completely by this. There's no question in my mind that with the huge difference in disease-free survival that we'd already seen for 3 years, it has become our standard of care really for this population at least to offer it, if not to strongly recommend it. But I would say that most of us have been quite inclined to recommend it, perhaps with caveats. And I would say that this overall survival benefit mostly corroborates that, even if there are some concerns about how these trials are done, but it's still an impressive difference that would lead me to only cement my practice of pursuing it in this setting. I just would love to re-examine how we conduct these trials and potentially potentiate disparities that exist and don't want to have our trials be more positive by capitalizing on that.

Dr. Vamsi Velcheti: Let's move on to the next abstract, LBA100; this is the KEYNOTE-671 trial. This was featured during the meeting's Clinical Science Symposium. This is a study of pembrolizumab or placebo plus platinum doublet followed by surgical resection and pembrolizumab or placebo for early-stage non-small cell lung cancer. Jack, what was the key message from this trial, and do you consider this as practice-changing?

Dr. Jack West: This has been an area where we've seen really dramatic evolution in our practice patterns, specifically, at least for patients who don't have a tumor harboring an EGFR mutation or ALK rearrangement. I would say that there has been some momentum toward preoperative neoadjuvant therapy, specifically based on the CheckMate-816 trial that gave chemo with nivolumab versus placebo and showed a significant improvement in the pathologic complete response rate at surgery as well as event-free survival. The overall survival looks encouraging but is still early and hasn't met the threshold for statistical significance, and that's FDA-approved.

But we still question whether there's a value to doing anything in the postoperative setting. And the CheckMate-816 trial did not include that as part of the trial. It allowed postoperative management at the judgment of the treating physician but didn't really prescribe anything. We now have the results of several trials in the last few months that have added a component in the postoperative setting in addition to three or four cycles of preoperative chemoimmunotherapy. And the first one that gave us a glimpse was the AEGEAN trial presented by Dr. John Heymach at AACR in April of this year that looked at chemo and durvalumab versus chemo placebo and then followed by a year of durvalumab versus placebo after surgery. That showed results in terms of major pathologic response and event-free survival that are significantly better with immunotherapy. Not clearly superior to what we would see with CheckMate-816.

And then even more recently, we saw a monthly Plenary presentation from ASCO with the Neotorch trial presented by Dr. Shun Lu of China. This was a Chinese trial only that presented results just for patients with stage 3 disease thus far. This included patients with stage 2 or stage 3, but what we saw is stage 3 results and that looked at chemo with toripalimab for 3 cycles versus placebo and then a year of checkpoint inhibitor or placebo. This also shows a benefit with the addition of immunotherapy, but not clear if that's better than what we can already achieve with neoadjuvant alone with the Checkmate-816 approach.

And then what we have now is a presentation and simultaneous publication by Dr. Heather Wakelee of KEYNOTE-671. And this is really almost the exact same trial design as AEGEAN. It's 4 cycles of platinum doublet chemotherapy and it is for patients with stage 2 to 3a disease. And this gave 4 cycles of chemotherapy with placebo or pembrolizumab. And then after surgery, patients would go on in the investigation arm to a year of pembrolizumab or to the additional year with placebo. And this shows a significant improvement in event-free survival with a hazard ratio of 0.58. It's most prominent in patients with high PD-L1, where the hazard ratio is 0.42. But there's still a benefit in patients with PD-L1 less than 1%, where it's 0.77. And there was a trend toward better overall survival here, hazard ratio of 0.73. It does not reach statistical significance at this early point. It's still preliminary but certainly looks encouraging. And there are also significant improvements in major pathologic response, where less than 10%, about a threefold difference from 30.2% with immunotherapy compared to 11% with placebo. And a very impressive improvement in pCR rate, which is 18.1% with the chemo and pembro compared to 4% with chemotherapy alone. Not surprisingly, when we look at event-free survival, it's best in the patients who achieve a pathologic complete response, but pembrolizumab improved outcomes in event-free survival even for those who didn't achieve a pCR.

The real question I would say is does the addition of a year of checkpoint inhibitor therapy postoperatively add to what we already achieve with those first three cycles with chemo-neo or 4 cycles with maybe one of these other options? And these trials can't answer that question because they just include them as a package deal. There's no way to tease apart right now the component of what incremental benefits you get from that. And it certainly adds a year of time coming in for every 3-week infusions. Even if you space that out, it's still a year of coming in and getting infusions, potential cumulative immune-related toxicities, and a lot of cost versus potentially being done. And I think that really is the big question at this point of do you want to recommend something when we don't really have a precedent for much benefit beyond the first 4 cycles? Perhaps. Certainly, we give maintenance pemetrexed and other immunotherapies and there can be benefit there. So, I wouldn't say you necessarily cap that. But if there is resistant disease after the first 4 cycles you've already given 3 cycles, how much benefit is there? How likely is it that you're going to eradicate the last cancer cells with more?

That said, I think many patients, and oncologists myself perhaps included, are going to be inclined to err on the side of possibly over-treating, but at least trying to give everything that is part of a widely studied, FDA-approved approach once these options become available. I just think it's going to end up as a careful discussion with each patient about whether they'd prefer to just say they're done or do that extra year and really feel that even if it comes back, they've done everything that made sense to try.

Dr. Vamsi Velcheti: Very good points, Jack. So let's move on to another abstract, which is the LBA9000. This is the KEYNOTE-789 trial. In my opinion, this is the most important negative phase 3 trial in lung cancer in a while. This is a trial looking at pemetrexed platinum with or without pembrolizumab in patients who have EGFR mutation-positive metastatic non-small cell lung cancer. So, what are your key takeaways, Jack?

Dr. Jack West: Well, I would say essentially we've been waiting to figure out what is the best treatment approach for patients with acquired resistance after osimertinib. And most of the patients had received osimertinib for their EGFR mutation-positive non-small cell. This is essentially KEYNOTE-189 being run in the EGFR mutation-positive patients after they've exhausted at least the major benefit of EGFR TKI therapy.

What we saw was a hazard ratio for progression-free survival of 0.8. It didn't quite make it across the threshold for efficacy, a significant difference. And so it missed that efficacy boundary. And overall survival, the hazard ratio is 0.84, also missing the efficacy boundary. When you look at the actual curves, they show modest separation, nothing eye-popping, certainly compared to some of the other trials we're talking about. But I wouldn't say they show no benefit. And I think that's, to me, why there's really still a role for a nuanced thought process and maybe some discussion about how negative this is. This is not, in my mind, stone-cold negative with no patients benefiting from immunotherapy. This is a trial that really suggests that there's a subset of patients who are benefiting from immunotherapy.

And we've also seen going back to subset analysis of the IMpower150 trial and also the ORIENT-31 trial with sintilimab and a bevacizumab biosimilar, another anti-VEGF inhibitor. These trials both really indicated a benefit in this population after EGFR TKI therapy of immunotherapy combined with VEGF. I think there could still be a value in there. I don't want to be a Pollyanna or too open-minded, but I think that there was at least a suggestion that this could still be a fruitful avenue. I think that this is still something we should do additional studies on that could bear fruit. I wouldn't close the door and categorically say this is just never going to translate to any benefit for any of these patients.

Dr. Vamsi Velcheti: The key thing, though, is, like in EGFR mutant patients I think in the previous studies as well, the response rates with single-agent PD-1 have been very minimal. And I think one of the things that's actually very important to highlight is in the operative setting, the early-stage setting, unfortunately, some of the trials with immunotherapy have included patients with an EGFR mutation. And now we have a treatment option for those patients within the adjuvant setting, especially osimertinib. We just heard from the ADAURA trial, which has a clear significant overall survival benefit. So I think it's really important to test for EGFR mutation in all stages. And if somebody with the early stage has an EGFR mutation, adjuvant immunotherapy, or perioperative immunotherapy may not be the best option for those patients.

Dr. Jack West: Right. I agree with that, although it is interesting that the KEYNOTE-671 trial did have some small population of patients with an EGFR mutation, and in that subset analysis, they seem to benefit from the pembrolizumab. I would not say that we should divert from ADAURA, but I'm just not as sure that our previous statement and mindset that immunotherapy just categorically doesn't work for patients with driver mutations is that simple.

First of all, there is some heterogeneity about which driver mutation, and the ALK-positive patients seem to really get no benefit. But I think there's still some questions about immunotherapy for EGFR. Certainly, patients with KRAS or BRAF V600E seem to benefit like the broader range of patients. And I would also say maybe it's different whether you're giving immunotherapy combined with chemotherapy versus as monotherapy. So that's why I'm just not that sure we really can characterize this that well yet.

The one additional point I would make about KEYNOTE-789 and the potential role of immunotherapy is that some experts in thoracic oncology and general oncologists alike may prefer to introduce chemotherapy at a time of progression, but keep the osimertinib going, maybe particularly for patients with brain metastases, whether current or a history of them, where we really feel that the osimertinib adds a critical component to CNS control. We don't want to ever give osimertinib or probably other EGFR TKIs concurrently with immunotherapy. So that's just a factor that we'd really want to consider when we're prioritizing where to fit in immunotherapy, if at all.

Dr. Vamsi Velcheti: Thank you, Jack. And let's move on to the next abstract, Abstract 9002. This is a pivotal study of results from the sunvozertinib, which is an EGFR exon 20 insertion site mutation drug. There's some very promising data. Jack, how do you feel this study is going to influence practice?

Dr. Jack West: Well, this is not an agent we have access to broadly yet, but I was quite impressed by it overall. I didn't mention it. We talked about it in the pre-ASCO discussion, and it was really one that I would mark as potentially practice-changing when we can get it. DZD 9008 or sunvozertinib is a potent inhibitor of exon 20 insertion mutations, and this was 97 patients, and the majority had had a couple of lines of prior therapy. They had to have gotten chemo, and the response rate was 60%, and it was really comparable efficacy with the different mutation subtypes.

I think that the main thing that I would want to clarify a little better in my own patient population is how well the drug is really tolerated. We talked about that there was not really much grade 3 toxicity and that's true, but diarrhea rates were 67%, even though it was grade 3 and just about 8%. But grade 2 diarrhea or grade 2 rash in patients who are on this therapy, we hope for a long time, I think is something we shouldn't minimize. And I think that particularly our mindset about toxicity needs to be different when we're talking about giving a treatment for 2 or 4 cycles and then being done with it versus something we hope we're going to be giving longitudinally. And we really don't want to minimize the potential impact on the quality of life of patients who are experiencing grade 2 rash, diarrhea, or paronychia for months and months, maybe more than a year at a time.

But that said, this is twice the response rate if not more than that of what we have already had for patients with this molecular aberration with an exon 20 insertion. So I think it's compelling and I think that it's going to be really valuable to offer to our patients. I just would like to clarify better how well patients who are actually on it are feeling when you incorporate the potentially chronic toxicity issues.

Dr. Vamsi Velcheti: Thank you, Jack. And let's move on to the last abstract. This the LUNAR study, LBA9005. This is a positive phase 3 study that looked at tumor-treating fields or TTF therapy with standard of care treatments in metastatic non-small-cell lung cancer following platinum failure. This has been talked about a lot at ASCO, and Jack I'm eager to hear your key takeaways about this study.

Dr. Jack West: Well, we knew from a press release several months ago, I think back in February, that there was a significant improvement in overall survival with the addition of tumor-treated fields. Again, this concept that electric fields can lead to antimitotic effect and potentially downstream induction of immunogenic cell death and enhanced immune response, that's at least the concept. And it's of course established, has utility in patients with glioblastoma, although kind of, I would say underutilized because it can be cumbersome. And I think that's one of the things we need to factor in is that this is not the easiest approach to pursue.

But we don't have that many therapies that improve overall survival significantly in previously treated patients with non-small cell lung cancer. So, I think there's good reason to focus on this and ask how beneficial it is. It was notable, it was pretty much an even split of patients enrolled on the trial, 276 patients total, but about half had gotten chemo but not gotten immunotherapy before. And then the other half, I would say the clear majority, had gotten immunotherapy as well as chemo and got docetaxel-based treatment.

And the overall survival benefit was significant for the intent to treat total population with a hazard ratio of 0.74 and a difference in 3-year survival of 18% favoring the addition of tumor-treating fields on the chest versus 7% in the patients who didn't. It really seemed to separate between the patients who had not had an immune checkpoint inhibitor and got tumor-treating fields with the checkpoint inhibitor where the hazard ratio is 0.63 and those who got tumor-treating fields with docetaxel where the hazard ratio was 0.81. So it really wasn't significant in this population.

Toxicity, no real surprises compared to what we already knew about tumor-treating fields. Mostly dermatitis, but I would say that one of the kind of unmeasured issues is that this is a device that people have to wear on their chest carrying a battery pack with them all day long. It's essentially all the waking day, and so I think that's at least cumbersome. I wouldn't call it prohibitive, but it's a challenge. And I think we need to really ask whether the juice is worth the squeeze, whether the benefit is that compelling. And I question that when we're talking about an agent that doesn't significantly move the needle against docetaxel alone.

Again, this is a population where in the U.S. we have ramucirumab to add to docetaxel. Not everyone does that. It's not uniform, but that has a statistically significant, though modest survival benefit associated with that. We don't do better than that with tumor treating fields. And so, I think that this is an option that merits discussion and some patients may opt for it, but I suspect that most of my patients would not find the absolute difference to be that compelling for the challenges it incurs. I don't know what your perspective is here.

Dr. Vamsi Velcheti: I completely agree, Jack. And I think the study design and just the fact that the standard of care has changed over the last 5, actually 6 years since the study has been open. And I'm not really so sure I could really make much sense of the data in terms of the standard of care combination with TTF providing more benefit. And I think there are more questions than answers here and I'm not so sure which populations would benefit the most. And I think, I hate to say this, but this is a nice proof of concept. I hate to say this because it's a phase 3 study and it's a positive phase 3 study, but it's clinical relevance with the current standard of care, I think, I'm not really sure how much of an impact this would really have.

Well, Jack, I've really enjoyed speaking with you about these key advances in lung cancer that were featured at the 2023 ASCO Annual Meeting. Our listeners will find links to all the studies discussed today in the transcript of this episode. Thank you so much, Jack, for joining us today.

Dr. Jack West: Always a pleasure. Thanks so much.

Dr. Vamsi Velcheti: And just like that, we've reached the end of another enriching episode. But remember, like all good things, this too must come to an end, but only until we meet again. We really would like your feedback on the podcast. If you enjoyed the podcast, please 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.

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Disclosures:

Dr. Vamsidhar Velcheti:

Honoraria: ITeos Therapeutics

Consulting or Advisory Role: Bristol-Myers Squibb, Merck, Foundation Medicine, AstraZeneca/MedImmune, Novartis, Lilly, EMD Serono, GSK, Amgen, Elevation Oncology, Taiho Oncology, Merus

Research Funding (Inst.): Genentech, Trovagene, Eisai, OncoPlex Diagnostics, Alkermes, NantOmics, Genoptix, Altor BioScience, Merck, Bristol-Myers Squibb, Atreca, Heat Biologics, Leap Therapeutics, RSIP Vision, GlaxoSmithKline

Dr. Jack West:

Honoraria: AstraZeneca, Genentech/Roche, Merck, Takeda, Mirati, Regneron, Amgen, Abbvie

Consulting or Advisory Role: AstraZeneca, Genentech/Roche, Merck, Takeda, Mirati Therapeutics, Regneron, Amgen, Abbvie, Summit Therapeutics

Speakers' Bureau: Takeda, Merck, AstraZeneca