In this JCO Article Insights episode, Dr. Joseph Matthew interviews authors Dr. Yang Zhang and Dr. Haiquan Chen about their recently published JCO article, "Phase III Study of Mediastinal Lymph Node Dissection for Ground Glass Opacity–Dominant Lung Adenocarcinoma"

TRANSCRIPT

Joseph Mathew: Welcome to the Journal of Clinical Oncology Article Insights episode for the August issue of the JCO. This is Joseph Mathew, editorial fellow for JCO, and today, it is my pleasure to have with us Dr. Haiquan Chen and Dr. Yang Zhang, authors of the recently published manuscript, "Phase 3 Study of Mediastinal Lymph Node Dissection for Ground-Glass Opacity-Dominant Lung Adenocarcinoma," which we will be discussing today. Dr. Chen is the Director of the Institute of Thoracic Oncology at Fudan University and the Chief of Thoracic Surgery at Fudan University Shanghai Cancer Center, where he is also the Head of Thoracic Oncology MDT and the Director of the Lung Cancer Center. Dr. Chen is a surgeon-scientist and a pioneer in developing individualized surgical strategies for early-stage non-small cell lung cancer. Dr. Zhang is a surgical oncologist and a member of the team which Dr. Chen leads at the Fudan University Shanghai Cancer Center.

Welcome Dr. Chen and Dr. Zhang. Thank you very much for accepting our invitation and joining us today as part of this podcast episode.

To summarize the salient points, this study presented the interim analysis of a multi-center, open-label, non-inferiority, randomized controlled trial investigating the necessity of systematic mediastinal lymph node dissection at the time of segmentectomy or lobectomy in patients with clinical stage T1N0M0 ground-glass opacity-dominant invasive lung adenocarcinoma, as defined by a consolidation-to-tumor ratio of 0.5 or less on thin-section computed tomography and a maximum tumor diameter of 3 cm or less. Eligible participants with intraoperatively confirmed invasive adenocarcinoma on frozen section analysis were randomized to either the systematic mediastinal lymph node dissection arm or to no mediastinal lymph node dissection. In the latter experimental group, mediastinal lymph nodes comprising the N2 nodal stations were not dissected, and the hilar nodes were variably addressed at the discretion of the operating surgeon.

The primary endpoint of the trial was disease-free survival at 3 years. Secondary endpoints included perioperative outcomes, the status of lymph node metastasis in the systemic lymph node dissection arm, and 3-year overall survival. Before the trial reached its accrual target, a pre-planned interim safety analysis set for the time point when enrollment reached 300 patients was performed. It was noted that while none of the patients in either arm had nodal metastasis on postoperative pathological evaluation, lymph node dissection-related intraoperative and postoperative complications were more commonly observed in the systematic lymph node dissection arm, including one life-threatening episode of massive bleeding. Since this met the predefined criteria for trial termination, and in accordance with the principle of non-maleficence, further recruitment was stopped and the trial terminated.

Although the 3-year disease-free survival and the overall survival for the enrolled patients were comparable, operative outcomes, including the duration of surgery, blood loss, chest tube duration, length of postoperative stay, and the rate of clinically significant complications, were significantly lower in the experimental arm compared with the systematic lymph node dissection group. The authors concluded that for well-selected patients, mediastinal nodal dissection could be omitted without adversely affecting oncological outcomes, representing a significant shift in current surgical practice, given that guidelines the world over recommend systematic lymph node dissection or sampling for all invasive lung cancers.

In summary, this study addressed a clinically relevant question with regard to the extent of nodal dissection, especially in the light of recent evidence recommending less extensive parenchymal dissections for early-stage non-small cell lung cancer, with the findings suggesting that invasive lung adenocarcinoma associated with ground-glass opacities of consolidation-to-tumor ratio up to 0.5 was an excellent predictor of tumor biology, and in clinical T1N0M0 lesions, a reliable predictor of negative mediastinal lymph node involvement.

So Dr. Chen and Dr. Zhang, could you tell us some more about what led you to do this research and the challenges which you faced while recruiting patients for this trial?

Dr. Yang Zhang: Dr. Mathew, thank you for your summary. The current clinical guidelines recommend systematic lymph node dissection or sampling for every patient with early-stage lung cancer, regardless of their lymph node status. And in our clinical practice, we observe that this procedure causes a lot of surgical complications including chylothorax and recurrent laryngeal nerve injury. Furthermore, dissecting the tumor-draining lymph nodes actually may potentially damage the body's anti-tumor immunity. So, Dr. Chen proposed the concept of selective lymph node dissection, which we aimed to dissect the metastatic lymph nodes, while at the same time we try to preserve as many uninvolved lymph nodes as possible.

So previously, we have conducted a series of retrospective studies to identify reliable predictors of nodal negative status in certain mediastinal zones, and we have performed a prospective observational phase 2 clinical trial to validate that the six criteria we proposed are 100% in predicting node-negative status. And this forms the basis for our phase 3 clinical trial.

Dr. Haiquan Chen: This trial is only one of the series of trials. The meaning of this trial you already said. And for a long time, from the surgeon's point of view, we considered minimally invasive surgery. It minimizes the size of the incision and minimizes the number of the holes we made. So, the true and the high-impact of minimally invasive, we make a concept of minimal dissection, that means organ-level minimally invasive. So we proposed the concept of minimally invasive 3.0, that means minimal incision, minimal dissection (that means organ-level minimal), and systemic minimally invasive.

So at first, we judged from the point of minimally invasive surgery. As long as immunotherapy is widely used in the clinical practice, we know immunotherapy, that means you use drugs to stimulate and activate the lymph node site. If we dissect all the metastatic lymph nodes, cut them out, how can we restimulate that lymph node site? So, from minimally invasive trauma and second, from the functional aspect, to try to save as many uninvolved lymph nodes as possible.

Joseph Mathew: Thank you, Dr. Chen. That's a very interesting concept that you alluded to even in the discussion of this paper, as to the potential role of the non-metastatic lymph nodes as immune reservoirs.

So, coming back to this paper, were there any challenges which you faced while recruiting patients for this trial?

Dr. Haiquan Chen: The criteria is very clear. That means invasive adenocarcinoma, that means most of the centimeter is 3.0 centimeter and also CTR ratio less than 0.5. And we can see that, you know, we did study about that. Even the invasive component of the subsolid nodule, it's bigger than the solid part. That means even the pure GGO, we can find out that there's still some invasive component. From this point of view, pure GGO and subsolid GGO, from this part of invasive carcinoma, that means it's a special clinical subtype that we, from retrospective study and also prospective study, we find out this group of patients, there are no mediastinal lymph node metastasis. So I think it's very important for this kind of group that we can avoid doing the mediastinal lymph node dissection. And we can do organ-level minimally invasive surgery. And also, we try to keep the patient's immune function as normal as possible.

Dr. Yang Zhang: Well, Dr. Mathew, we believe that the biggest challenge when we are enrolling these patients is that there needs to be a paradigm shift in the mind because systematic lymph node dissection has long been the standard of care. And some patients may misunderstand. Before the enrollment, we have to give them informed consent, but if the patient hears that they may be enrolled in the no-lymph-node-dissection group, they may feel that they do not receive radical, curative-intent surgery. So we believe, as Dr. Chen has said, after the release of our results, the no-lymph-node dissection may be incorporated in the future guideline for those patients without lymph node involvement, we can just omit the lymph node dissection.

Joseph Mathew: The study described two pre-planned interim points during the course of subject enrollment when the data was analyzed. So Dr. Chen and Dr. Zhang, could you please explain a little more about these two interim points of analysis that were planned and the rationale behind it?

Dr. Yang Zhang: When conducting this trial, we have two concerns. One is if there is any lymph node metastasis, there may be omission of metastatic lymph nodes not dissected in the no-lymph-node-dissection group. And there is another concern is that if all these lymph nodes are uninvolved, then dissecting these lymph nodes may cause life-threatening complications. So, we set the 150 interim analysis to ensure that there is no lymph node involvement in this group. And the other early termination criteria is set because if there is no lymph node involvement found in both groups, then a severe complication which is life-threatening is unacceptable because it threatens the patient's safety.

Joseph Mathew: So, although you did briefly allude to in the paper, what was the basis for selecting DFS as the primary endpoint when the objective of this trial was to assess nodal involvement in this subset of tumors?

Dr. Yang Zhang: Well, previously, we have done a series of retrospective studies and one prospective phase 2 trial. And in these studies, we have identified that GGO-dominant lung adenocarcinoma, even if it's invasive, it has no lymph node involvement. So this phase 3 trial was primarily designed to compare the survival outcomes. But as the trial went on, as Dr. Chen has concerns that if the patients have no lymph node metastasis at all, it may be unfair to dissect the lymph nodes for patients enrolled in the systematic lymph node dissection group. So there is one life-threatening complication that happens due to dissecting the lymph nodes and injury to the superior vena cava, which leads to massive bleeding. It is at this point that we decided to terminate this trial for patient safety concerns.

Joseph Mathew: Yeah, that's a very fair point. So you made sure that the ethical considerations were kept intact.

So another point was, there was a mention in the study of the historical data from your institution suggesting a 3-year disease-free survival of 96.6% for patients with clinical T1N0M0 ground-glass opacity-dominant invasive lung adenocarcinoma. So could you please elaborate on the patterns of recurrence which you noted for this group of patients who had developed a recurrence?

Dr. Haiquan Chen: Yeah, I think over 90% 3-year DFS, that's the least. From our retrospective data for this kind of group of patients, their DFS is so good. To the best of my knowledge, almost 100%. So this is very conservative, 94, 90% is very conservative. I think the trial eventually would have been positive. It's a special clinical subtype, even for invasive adenocarcinoma, their prognosis is much better than the other type of invasive adenocarcinoma.

Joseph Mathew: So this question may be slightly outside the purview of this study, but in your clinical practice, would you advocate either segmentectomy or lobectomy for all patients meeting the trial criteria, that is, lesions measuring 3 cm or less with a CTR of up to 0.5? Or is there a subgroup of patients you would recommend a wedge dissection for?

Dr. Haiquan Chen: I think CTR ratio is one parameter and also the location is another very important parameter. So we put it together to make a decision, the patient should do a lobectomy or segmentectomy. Even for an ongoing trial, for even the patient, invasive adenocarcinoma, we can do in the right location, even wedge, it can achieve enough negative margin in the ongoing trial to verify the comparable result for the patient, we can do the wedge dissection. So not just the CTR ratio, that's not the only parameter to make a decision on what kind of procedure we'll do.

Joseph Mathew: Yeah, great point, Dr. Chen. So from my perspective, this study was a well-designed, randomized control trial based on a relevant and clinically valid research question. So what, in your opinion, are the main strong points of this study?

Dr. Yang Zhang: We believe that this study represents the first randomized clinical trial published, yet, regarding the topic of selective lymph node dissection. It basically offers the highest level of evidence. We believe our results should be incorporated in the future clinical guideline.

Joseph Mathew: Given the increasing incidence of these lesions, I think it was- a randomized control trial in this arena was much awaited. And the other point is that GGO-dominant lung adenocarcinomas, the specific clinical guidelines are not very clear. So I think your study brought out that lymph node dissection for these tumors which satisfy the eligibility criteria could be omitted safely. Important consideration here is that the conclusions of the trial were based on an interim analysis, and this analysis was not planned for an early assessment of the primary endpoint. In other words, the study was not adequately powered to detect a significant difference in DFS at 3 years.

So Dr. Chen and Dr. Zhang, what do you perceive are the most important limitations of this study which you feel should be addressed in future research?

Dr. Haiquan Chen: So the surgery now is more individualized. I think the surgery from the last two decades, from the maximum tolerable intervention to minimum effective treatment, there's a big shift. So I think that the consensus, we can preserve normal lung parenchyma as much as possible. For the lymph nodes, I think that the big shift, we should shift it to keep as many as uninvolved lymph nodes as possible. So that's very important, not just to reduce the intraoperative trauma, but also to keep the immune environment as normal as possible.

Joseph Mathew: Another point was the limited long-term follow-up data to determine the actual impact of omitting lymph node dissection on local-regional disease control. So is any future follow-up planned to assess the long-term survival outcomes for the 302 patients which were enrolled in this trial?

Dr. Haiquan Chen: Yeah, I think that's very important for us. This trial we terminated just because if we keep the trial going, it's unfair for the mediastinal lymph node dissection group. We tried to just stop here, and we shifted to the single-arm trial. So, 2 or 3 years, this trial and another trial, they will give our final result to demonstrate more if selective mediastinal lymph nodes have a better result than ever before. And we will support the mediastinal lymph node dissection. That's one way.

And the American College just asked me, how can we put this policy into clinical practice in the United States? Because most of the patients they meet have solid tumors. So we have another trial, try to figure out how we can make sure before and intraoperative the lymph node status is negative or positive, and then we can solve that problem and put this policy into clinical practice in the Western society.

Joseph Mathew: Great. So that would be something we should all be looking forward to. So, this brings me to the final point of discussion on future research in this field. Dr. Chen, you commented in the paper that future studies should focus on improving the reproducibility of CTR evaluation. What are your thoughts on this subject?

Dr. Haiquan Chen: The CTR ratio, the concept from the JCOG 0201, just a concept from that prospective study, the phase 2 study, only subgroup analysis they give the concept of CTR ratio and the diameter. How can we reproduce? In our group and also I believe in Japan and in China, in Korea, and in our daily practice, I think CTR ratio is not a big issue. There are two very important things. One, you make sure the CTR ratio, not in a common CAT scan, but in a high-resolution CAT scan. So the imaging, that's the first thing. And the second, not from the single section and a two or three section, you make sure that your calculation is accurate. That's not just the single section, you make sure that you got the conclusion, the CTR ratio is the same number. We make sure that totally we, from the top to the bottom of the whole lesion, we make sure that the CTR ratio is accurate.

Joseph Mathew: Thank you, Dr. Chen. I think that would involve training our radiologists also to be aware of the CTR ratio and how it should be interpreted.

So another very interesting concept which you had alluded to in the discussion was the potential role of non-metastatic lymph nodes as immune reservoirs. So how do you think we could preserve these nodes and do you think sentinel node biopsies would play a role in future?

Dr. Yang Zhang: Actually, Dr. Chen has also led some basic research on this topic. We are investigating the immunological role of the tumor-draining lymph nodes. And our preliminary results have already shown that the tumor-draining lymph nodes of lung cancer, especially those uninvolved lymph nodes, have a vital role in the anti-tumor immunity and also effective response to the current anti-PD-1 immunotherapy. In the future, we believe that by incorporating our clinical evidence and those findings from our basic research, we will be able to provide very strong rationale to support selective lymph node dissection.

Joseph Mathew: So lastly, what are the questions that still remain to be answered and what do you perceive as the next step in this field?

Dr. Haiquan Chen: I think for the lung cancer surgery, especially for the cT1N0M0, they are more individualized. We can, based on the patient, the location, the CTR ratio, we can do wedge dissection, or segmentectomy, or lobectomy. For the lymph node dissection, we can do no mediastinal lymph node dissection or selective, only to dissect the positive one, or we have to do the systemic mediastinal lymph node dissection. So we can see there are too many combinations. So in the near future, for the surgery perspective, we have it more individualized. In the future, we just try to make sure we do not cut as many as possible. We just make sure that we can avoid over-diagnosis or overtreatment or over-dissected. I think that in the near future, that goal will come true.

Joseph Mathew: That's a great point, Dr. Chen. So that would be something also for the thoracic oncology community to work towards.

This wraps up today's episode of JCO Article Insights. Dr. Chen and Dr. Zhang, thank you very much for taking the time to join us today in what has been a very insightful session.

Dr. Haiquan Chen: Thank you.

Dr. Yang Zhang: Thanks.

Joseph Mathew: To our audience, thank you for listening. Please stay tuned for more interviews and articles, summaries, and be sure to leave us your comments and ratings. For more podcasts and episodes from ASCO, please visit asco.org/podcasts.

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JCO Article Insights: Lymph Node Dissection for Lung Cancer

Journal of Clinical Oncology (JCO) Podcast

JCO Article Insights: Lymph Node Dissection for Lung Cancer