Chemotherapy and Targeted Therapy for HER2-Negative Metastatic Breast Cancer that is Either Endocrine-Pretreated or Hormone Receptor–Negative: ASCO Guideline Rapid Recommendation Update

An interview with Dr. Beverly Moy from Massachusetts General Hospital in Boston, MA, lead author on "Chemotherapy and Targeted Therapy for HER2-Negative Metastatic Breast Cancer That is Either Endocrine-Pretreated or Hormone Receptor-Negative: ASCO Guideline Rapid Recommendation Update." Dr. Moy reviews data from the recently published DESTINY-Breast04 study, and the ASCO Expert Panel's updated recommendation on the use of trastuzumab deruxtecan. For more information, visit www.asco.org/breast-cancer-guidelines.

TRANSCRIPT

Brittany Harvey: Hello, and welcome to the ASCO Guideline 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. Beverly Moy from Massachusetts General Hospital in Boston, Massachusetts, lead author on 'Chemotherapy and Targeted Therapy for HER2-Negative Metastatic Breast Cancer That is Either Endocrine-Pretreated or Hormone Receptor-Negative: ASCO Guideline Rapid Recommendation Update'. Thank you for being here, Dr. Moy.

Dr. Beverly Moy: It's my pleasure. Thank you for having me.

Brittany Harvey: Great. First, 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 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. Moy, do you have any relevant disclosures that are directly related to this guideline topic?

Dr. Beverly Moy: I do not have any relevant disclosures that are directly relevant to this guideline topic.

Brittany Harvey: Thank you. Then let's talk about this rapid update. So first, what prompted a rapid update to this guideline on chemotherapy and targeted therapy for patients with HER2-negative metastatic breast cancer that is either endocrine-pretreated or hormone receptor-negative, which was last updated in 2021?

Dr. Beverly Moy: First, I would state that ASCO issues rapid guideline recommendation updates when really important advances in the treatment and management of cancer have been presented. This mechanism really allows clinicians to keep up with the rapid advances in cancer management. The fact that a rapid update had to be issued just one year after the full updated guideline that was published in 2021, as you just mentioned, is really a testament to the advances in cancer research and clinical trials that have been made recently.

But I will state that the reason why this rapid update was done was because the result of the DESTINY-Breast04 study were so strong and compelling and showed such a large degree of benefit to a large group of metastatic breast cancer patients that we felt as the guideline panel that this rapid update had to be out there. We really wanted to make sure that the oncology community was aware of these results. That's based on the strength of the trial. The DESTINY-Breast04 trial was a very large randomized study that showed that trastuzumab deruxtecan significantly improved progression-free survival and overall survival compared to treatment of physician's choice in patients with metastatic, "HER2-low" breast cancer.

Brittany Harvey: So then based off this new data from the DESTINY-Breast04 trial that you just mentioned, what is the updated recommendation from the guideline expert panel?

Dr. Beverly Moy: So the updated recommendation is that patients with HER2-low, or to be specific, HER2 IHC1+ or 2+ and ISH negative metastatic breast cancer who have received at least one prior chemotherapy for metastatic disease, if they're hormone receptor-positive, are refractory to endocrine therapy, those patients should be offered treatment with trastuzumab deruxtecan.

Brittany Harvey: And then what should clinicians know as they implement this new recommendation for trastuzumab deruxtecan?

Dr. Beverly Moy: I think that there are a few things that clinicians really need to be aware of. One is that it significantly improved progression-free survival and overall survival, and that's pretty important. The paper was published in the New England Journal of Medicine, and folks can refer to that study specifically. But to be specific, it improved progression-free survival at a median follow-up of about 18 months from 9.9 months with trastuzumab deruxtecan compared to 5.1 months with treatment of physician choice in the entire study population. Median overall survival was 23.4 months with trastuzumab deruxtecan and 16.8 months with treatment of physician's choice. So that's really a marked improvement in both of those outcomes.

It is also important to note that trastuzumab deruxtecan has a very important side effect, and that's the potential of developing drug-related interstitial lung disease or pneumonitis. And that could be very serious. This side effect was confirmed in about 12% of the patients who received trastuzumab deruxtecan, and about 1.3% of patients actually had severe symptoms requiring oxygen, and three patients in the study, so less than 1% actually died of this side effect. So that's something that needs to be monitored for very carefully, and clinicians need to be very cognizant of this potential side effect when using this drug.

Brittany Harvey: Thank you for reviewing both the impact on survival and then the adverse event of interstitial lung disease. So how does this guideline update impact patients with breast cancer?

Dr. Beverly Moy: So metastatic breast cancer is incredibly common. And this HER2-low, and I say, "HER2-low" because this is a definition that has never been made before. The patients with HER2 IHC1+ or 2+ and ISH negative disease, that's a very large group of patients. That's a lot of patients. So it's really important that this guideline is going to impact a very large group of patients. Again, it's those who've had at least one prior line of chemotherapy in the metastatic setting. And if they had hormone receptor-positive disease, it has to be refractory to endocrine therapy. But that's a lot of patients. And the results of this randomized study do show that trastuzumab deruxtecan is superior to other treatment of physician's choices that were available before this study came out in terms of its efficacy. So this guideline is very significant for clinicians and metastatic breast cancer patients across the world.

Brittany Harvey: Definitely. It's great to have a new option and one that has such a great clinical impact for patients.

So then finally, Dr. Moy, what are the outstanding questions regarding chemotherapy and targeted therapy for HER2-negative metastatic breast cancer?

Dr. Beverly Moy: I think like any good study, this raises a lot of other important questions. Again, this HER2-low definition that I described is an interesting one. It's a very large bucket of patients. One obvious question is, would this drug be as effective in patients who are truly HER2-negative, so HER2 IHC of 0? Kind of, overnight, the results of this study has changed the paradigm for many oncologists because we used to just say HER2-positive or HER2-negative. And now we're looking back at patients' charts to see what their immunohistochemistry results were. Does it really matter if it's IHC 0 or 1+ or 2+? So that would be very interesting.

Another outstanding question is: what about the use of trastuzumab deruxtecan earlier in the treatment? I said that it should be offered for patients who've received at least one prior line of chemotherapy? What about first line chemotherapy in the metastatic setting? And there are multiple studies studying this drug in actually early stage breast cancer as well. So lots of unanswered questions about this compound that's pretty remarkable.

Brittany Harvey: Great. Well, I want to thank you so much for your time today, Dr. Moy, for discussing the results of the DESTINY-Breast04 trial with me, and for your work to rapidly update this guideline.

Thank you so much.

Dr. Beverly Moy: Thank you, Brittany. It was a pleasure.

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/breast-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 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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