Dr. Ko Un “Clara” Park and Dr. Mylin Torres present the latest evidence-based changes to the SLNB in early-stage breast cancer guideline. They discuss the practice-changing trials that led to the updated recommendations and topics such as when SLNB can be omitted, when ALND is indicated, radiation and systemic treatment decisions after SLNB omission, and the role of SLNB in special circumstances. We discuss the importance of shared decision-making and other ongoing and future de-escalation trials that will expand knowledge in this space. Read the full guideline update, “Sentinel Lymph Node Biopsy in Early-Stage Breast Cancer: ASCO Guideline Update” at www.asco.org/breast-cancer-guidelines.

TRANSCRIPT

This guideline, clinical tools, and resources are available at http://www.asco.org/breast-cancer-guidelines. Read the full text of the guideline and review authors’ disclosures of potential conflicts of interest in the Journal of Clinical Oncology, https://ascopubs.org/doi/10.1200/JCO-25-00099      

Brittany Harvey: Hello and welcome to the ASCO Guidelines podcast, one of ASCO's podcasts delivering timely information to keep you up to date on the latest changes, challenges and advances in oncology. You can find all the shows, including this one at asco.org/podcasts.

My name is Brittany Harvey and today I'm interviewing Dr. Ko Un "Clara" Park from Brigham and Women's Hospital, Dana-Farber Cancer Institute, and Dr. Mylin Torres from Glenn Family Breast Center at Winship Cancer Institute of Emory University, co-chairs on “Sentinel Lymph Node Biopsy in Early-Stage Breast Cancer: ASCO Guideline Update.”

Thank you for being here today, Dr. Park and Dr. Torres.

Dr. Mylin Torres: Thank you, it's a pleasure to be here.

Brittany Harvey: And before we discuss this guideline, 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 disclosures of potential conflicts of interest for the guideline panel, including Dr. Torres and Dr. Park, who have joined us here today, are available online with the publication of the guideline in the Journal of Clinical Oncology, which is linked in the show notes.

To start us off, Dr. Torres, what is the scope and purpose of this guideline update on the use of sentinel lymph node biopsy in early-stage breast cancer?

Dr. Mylin Torres: The update includes recommendations incorporating findings from trials released since our last published guideline in 2017. It includes data from nine randomized trials comparing sentinel lymph node biopsy alone versus sentinel lymph node biopsy with a completion axillary lymph node dissection. And notably, and probably the primary reason for motivating this update, are two trials comparing sentinel lymph node biopsy with no axillary surgery, all of which were published from 2016 to 2024. We believe these latter two trials are practice changing and are important for our community to know about so that it can be implemented and essentially represent a change in treatment paradigms.

Brittany Harvey: It's great to hear about these practice changing trials and how that will impact these recommendation updates.

So Dr. Park, I’d like to start by reviewing the key recommendations across all of these six overarching clinical questions that the guideline addressed. So first, are there patients where sentinel lymph node biopsy can be omitted?

Dr. Ko Un "Clara" Park: Yes. The key change in the current management of early-stage breast cancer is the inclusion of omission of sentinel lymph node biopsy in patients with small, less than 2 cm breast cancer and a negative finding on preoperative axillary ultrasound. The patients who are eligible for omission of sentinel lymph node biopsy according to the SOUND and INSEMA trial are patients with invasive ductal carcinoma that is size smaller than 2 cm, Nottingham grades 1 and 2, hormone receptor-positive, HER2-negative in patients intending to receive adjuvant endocrine therapy, and no suspicious lymph nodes on axillary ultrasound or if they have only one suspicious lymph node, then the biopsy of that lymph node is benign and concordant according to the axillary ultrasound findings. The patients who are eligible for sentinel lymph node biopsy omission according to the SOUND and INSEMA trials were patients who are undergoing lumpectomy followed by whole breast radiation, especially in patients who are younger than 65 years of age. For patients who are 65 years or older, they also qualify for omission of sentinel lymph node biopsy in addition to consideration for radiation therapy omission according to the PRIME II and CALGB 9343 clinical trials. And so in those patients, a more shared decision-making approach with the radiation oncologist is encouraged.

Brittany Harvey: Understood. I appreciate you outlining that criteria for when sentinel lymph node biopsy can be omitted and when shared decision making is appropriate as well.

So then, Dr. Torres, in those patients where sentinel lymph node biopsy is omitted, how are radiation and systemic treatment decisions impacted?

Dr. Mylin Torres: Thank you for that question. I think there will be a lot of consternation brought up as far as sentinel lymph node biopsy and the value it could provide in terms of knowing whether that lymph node is involved or not. But as stated, sentinel lymph node biopsy actually can be safely omitted in patients with low risk disease and therefore the reason we state this is that in both SOUND and INSEMA trial, 85% of patients who had a preoperative axillary ultrasound that did not show any signs of a suspicious lymph node also had no lymph nodes involved at the time of sentinel node biopsy. So 85% of the time the preoperative ultrasound is correct. So given the number of patients where preoperative ultrasound predicts for no sentinel node involvement, we have stated within the guideline that radiation and systemic treatment decisions should not be altered in the select patients with low risk disease where sentinel lymph node biopsy can be omitted. Those are the patients who are postmenopausal and age 50 or older who have negative findings on preoperative ultrasound with grade 1 or 2 disease, small tumors less than or equal to 2 cm, hormone receptor-positive, HER2-negative breast cancer who undergo breast conserving therapy.

Now, it's important to note in both the INSEMA and SOUND trials, the vast majority of patients received whole breast radiation. In fact, within the INSEMA trial, partial breast irradiation was not allowed. The SOUND trial did allow partial breast irradiation, but in that study, 80% of patients still received whole breast treatment. Therefore, the preponderance of data does support whole breast irradiation when you go strictly by the way the SOUND and INSEMA trials were conducted. Notably, however, most of the patients in these studies had node-negative disease and had low risk features to their primary tumors and would have been eligible for partial breast irradiation by the ASTRO Guidelines for partial breast treatment. So, given the fact that 85% of patients will have node-negative disease after a preoperative ultrasound, essentially what we're saying is that partial breast irradiation may be offered in these patients where omission of sentinel node biopsy is felt to be safe, which is in these low risk patients.

Additionally, regional nodal irradiation is something that is not indicated in the vast majority of patients where omission of sentinel lymph node biopsy is prescribed and recommended, and that is because very few of these patients will actually end up having pathologic N2 disease, which is four or more positive lymph nodes. If you look at the numbers from both the INSEMA and the SOUND trial, the number of patients with pathologic N2 disease who did have their axilla surgically staged, it was less than 1% in both trials. So, in these patients, regional nodal irradiation, there would be no clear indication for that more aggressive and more extensive radiation treatment.

The same principles apply to systemic therapy. As the vast majority of these patients are going to have node-negative disease with a low risk primary tumor, we know that postmenopausal women, even if they're found to have one to three positive lymph nodes, a lot of the systemic cytotoxic chemotherapy decisions are driven by genomic assay score which is taken from the primary tumor. And therefore nodal information in patients who have N1 disease may not be gained in patients where omission of sentinel lymph node biopsy is indicated in these low risk patients. 14% of patients have 1 to 3 positive lymph nodes in the SOUND trial and that number is about 15% in the INSEMA trial. Really only the clinically actionable information to be gained is if a patient has four or more lymph nodes or N2 disease in this low risk patient population. So, essentially when that occurs it's less than 1% of the time in these patients with very favorable primary tumors. And therefore we thought it was acceptable to stand by a recommendation of not altering systemic therapy or radiation recommendations based on omission of sentinel nodes because the likelihood of having four more lymph nodes is so low.

Dr. Ko Un "Clara" Park: I think one thing to add is the use of CDK4/6 inhibitors to that and when we look at the NATALEE criteria for ribociclib in particular, where node-negative patients were included, the bulk majority of the patients who were actually represented in the NATALEE study were stage III disease. And for stage I disease to upstage into anatomic stage III, that patient would need to have pathologic N2 disease. And as Dr. Torres stated, the rate of having pathologic N2 disease in both SOUND and INSEMA studies were less than 1%. And therefore it would be highly unlikely that these patients would be eligible just based on tumor size and characteristics for ribociclib. So we think that it is still safe to omit sentinel lymph node biopsy and they would not miss out, if you will, on the opportunity for CDK4/6 inhibitors.

Brittany Harvey: Absolutely. I appreciate you describing those recommendations and then also the nuances of the evidence that's underpinning those recommendations, I think that's important for listeners.

So Dr. Park, the next clinical question addresses patients with clinically node negative early stage breast cancer who have 1 or 2 sentinel lymph node metastases and who will receive breast conserving surgery with whole breast radiation therapy. For these patients, is axillary lymph node dissection needed?

Dr. Ko Un "Clara" Park: No. And this is confirmed based on the ACOSOG Z0011 study that demonstrated in patients with 1 to 3 positive sentinel lymph node biopsy when the study compared completion axillary lymph node dissection to no completion axillary lymph node dissection, there was no difference. And actually, the 10-year overall survival as reported out in 2017 and at a median follow up of 9.3 years, the overall survival again for patients treated with sentinel lymph node biopsy alone versus those who were treated with axillary lymph node dissection was no different. It was 86.3% in sentinel lymph node biopsy versus 83.6% and the p-value was non-inferior at 0.02. And so we believe that it is safe for the select patients who are early stage with 1 to 2 positive lymph nodes on sentinel lymph node biopsy, undergoing whole breast radiation therapy to omit completion of axillary lymph node dissection.

Brittany Harvey: Great, I appreciate you detailing what's recommended there as well.

So then, to continue our discussion of axillary lymph node dissection, Dr. Torres, for patients with nodal metastases who will undergo mastectomy, is axillary lymph node dissection indicated?

Dr. Mylin Torres: It's actually not and this is confirmed by two trials, the AMAROS study as well as the SENOMAC trial. And in both studies, they compared a full lymph node dissection versus sentinel lymph node biopsy alone in patients who are found to have 1 to 2 positive lymph nodes and confirmed that there was no difference in axillary recurrence rates, overall survival or disease-free survival. What was shown is that with more aggressive surgery completion axillary lymph node dissection, there were higher rates of morbidity including lymphedema, shoulder pain and paresthesias and arm numbness, decreased functioning of the arm and so there was only downside to doing a full lymph node dissection.

Importantly, in both trials, if a full lymph node dissection was not done in the arm that where sentinel lymph node biopsy was done alone, all patients were prescribed post mastectomy radiation and regional nodal treatment and therefore both studies currently support the use of post mastectomy radiation and regional nodal treatment when a full lymph node dissection is not performed in these patients who are found to have N1 disease after a sentinel node biopsy.

Brittany Harvey: Thank you.

And then Dr. Park, for patients with early-stage breast cancer who do not have nodal metastases, can completion axillary lymph node dissection be omitted?

Dr. Ko Un "Clara" Park: Yes, and this is an unchanged recommendation from the earlier ASCO Guidelines from 2017 as well as the 2021 joint guideline with Ontario Health, wherein patients with clinically node-negative early stage breast cancer, the staging of the axilla can be performed through sentinel lymph nodal biopsy and not completion axillary lymph node dissection.

Brittany Harvey: Understood.

So then, to wrap us up on the clinical questions here, Dr. Park, what is recommended regarding sentinel lymph node biopsy in special circumstances in populations?

Dr. Ko Un "Clara" Park: One key highlight of the special populations is the use of sentinel lymph node biopsy for evaluation of the axilla in clinically node negative multicentric tumors. While there are no randomized clinical trials evaluating specifically the role of sentinel lymph nodal biopsy in multicentric tumors, in the guideline, we highlight this as one of the safe options for staging of the axilla and also for pregnant patients, these special circumstances, it is safe to perform sentinel lymph node biopsy in pregnant patients with the use of technetium - blue dye should be avoided in this population.

In particular, I want to highlight where sentinel lymph node biopsy should not be used for staging of the axilla and that is in the population with inflammatory breast cancer. There are currently no studies demonstrating that sentinel lymph node biopsy is oncologically safe or accurate in patients with inflammatory breast cancer. And so, unfortunately, in this population, even after neoadjuvant systemic therapy, if they have a great response, the current guideline recommends mastectomy with axillary lymph node dissection.

Brittany Harvey: Absolutely. I appreciate your viewing both where sentinel lymph node can be offered in these special circumstances in populations and where it really should not be used.

So then, Dr. Torres, you talked at the beginning about how there's been these new practice changing trials that really impacted these recommendations. So in your view, what is the importance of this guideline update and how does it impact both clinicians and patients?

Dr. Mylin Torres: Thank you for that question. This update and these trials that inform the update represent a significant shift in the treatment paradigm and standard of care for breast cancer patients with early-stage breast cancer. When you think about it, it seems almost counterintuitive that physicians and patients would not want to know if a lymph node is involved with cancer or not through sentinel lymph node biopsy procedure. But what these studies show is that preoperative axillary ultrasound, 85% of the time when it's negative, will correctly predict whether a sentinel lymph node is involved with cancer or not and will also be negative. So if you have imaging that's negative, your surgery is likely going to be negative.

Some people might ask, what's the harm in doing a sentinel lymph node biopsy? It's important to recognize that upwards of 10% of patients, even after sentinel lymph node biopsy will develop lymphedema, chronic arm pain, shoulder immobility and arm immobility. And these can have a profound impact on quality of life. And if there is not a significant benefit to assessing lymph nodes, particularly in someone who has a preoperative axillary ultrasound that's negative, then why put a patient at risk for these morbidities that can impact them lifelong? Ideally, the adoption of omission of sentinel lymph node biopsy will lead to more multidisciplinary discussion and collaboration in the preoperative setting especially with our diagnostic physicians, radiology to assure that these patients are getting an axillary ultrasound and determine how omission of sentinel lymph node biopsy may impact the downstream treatments after surgery, particularly radiation and systemic therapy decisions, and will be adopted in real world patients, and how clinically we can develop a workflow where together we can make the best decisions for our patients in collaboration with them through shared decision making.

Brittany Harvey: Absolutely. It's great to have these evidence-based updates for clinicians and patients to review and refer back to.

So then finally, Dr. Park, looking to the future, what are the outstanding questions and ongoing trials regarding sentinel lymph node biopsy in early-stage breast cancer?

Dr. Ko Un "Clara" Park: I think to toggle on Dr. Torres’s comment about shared decision making, the emphasis on that I think will become even more evident in the future as we incorporate different types of de-escalation clinical studies. In particular, because as you saw in the SOUND and INSEMA studies, when we de-escalate one modality of the multimodality therapy, i.e., surgery, the other modalities such as radiation therapy and systemic therapy were “controlled” where we were not de-escalating multiple different modalities. However, as the audience may be familiar with, there are other types of de-escalation studies in particular radiation therapy, partial breast irradiation or omission of radiation therapy, and in those studies, the surgery is now controlled where oftentimes the patients are undergoing surgical axillary staging.

And conversely when we're looking at endocrine therapy versus radiation therapy clinical trials, in those studies also the majority of the patients are undergoing surgical axillary staging. And so now as those studies demonstrate the oncologic safety of omission of a particular therapy, we will be in a position of more balancing of the data of trying to select which patients are the safe patients for omission of certain types of modality, and how do we balance whether it's surgery, radiation therapy, systemic therapy, endocrine therapy. And that's where as Dr. Torres stated, the shared decision making will become critically important.

I'm a surgeon and so as a surgeon, I get to see the patients oftentimes first, especially when they have early-stage breast cancer. And so I could I guess be “selfish” and just do whatever I think is correct. But whatever the surgeon does, the decision does have consequences in the downstream decision making. And so the field really needs to, as Dr. Torres stated earlier, rethink the workflow of how early-stage breast cancer patients are brought forth and managed as a multidisciplinary team.

I also think in future studies the expansion of the data to larger tumors, T3, in particular,reater than 5 cm and also how do we incorporate omission in that population will become more evident as we learn more about the oncologic safety of omitting sentinel lymph node biopsy.

Dr. Mylin Torres: In addition, there are other outstanding ongoing clinical trials that are accruing patients right now. They include the BOOG 2013-08 study, SOAPET, NAUTILUS and the VENUS trials, all looking at patients with clinical T1, T2N0 disease and whether omission of sentinel lymph node biopsy is safe with various endpoints including regional recurrence, invasive disease-free survival and distant disease-free survival.

I expect in addition to these studies there will be more studies ongoing even looking at the omission of sentinel lymph node biopsy in the post-neoadjuvant chemotherapy setting. And as our imaging improves in the future, there will be more studies improving other imaging modalities, probably in addition to axillary ultrasound in an attempt to accurately characterize whether lymph nodes within axilla contain cancer or not, and in that context whether omission of sentinel lymph node biopsy even in patients with larger tumors post-neoadjuvant chemotherapy may be done safely and could eventually become another shift in our treatment paradigm.

Brittany Harvey: Yes. The shared decision making is key as we think about these updates to improve quality of life and we'll await data from these ongoing trials to inform future updates to this guideline.

So I want to thank you both so much for your extensive work to update this guideline and thank you for your time today. Dr. Park and Dr. Torres.

Dr. Mylin Torres: Thank you.

Dr. Ko Un "Clara" Park: Thank you.

Brittany Harvey: And thank you to all of our listeners for tuning in to the ASCO Guidelines podcast. To read the full guideline, go to www.asco.org/breast-cancer-guidelines. You can also find many of our guidelines and interactive resources in the free ASCO Guidelines app available in the Apple App Store or the Google Play Store. If you have 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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