Endocrine and Targeted Therapy for HR-Positive, HER2-Negative Metastatic Breast Cancer – Capivasertib-Fulvestrant: Rapid Guideline Update

Dr. Angela DeMichele, Dr. Lynn Henry, and Dr. Harold Burstein present the latest breast cancer rapid recommendation update impacting two ASCO guidelines. This update focuses on the new option, capivasertib plus fulvestrant, for patients with hormone receptor-positive, HER2-negative metastatic breast cancer with activating PIK3CA or AKT1 mutations or inactivating alterations in PTEN based on data from the recent CAPItello-291 trial. They discuss the updated recommendations on lines of endocrine treatment and selecting between the options for patients with activating PIK3CA mutations. Additionally, we discuss implications for clinicians and patients, and what ongoing research is occurring in the field.

Read the latest update, “Endocrine and Targeted Therapy for Hormone Receptor-Positive, HER2-Negative Metastatic Breast Cancer – Capivasertib-Fulvestrant: ASCO Rapid Guideline Update“ at www.asco.org/breast-cancer-guidelines.

TRANSCRIPT

This guideline, clinical tools, and resources are available at 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.24.00248

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 am interviewing Dr. Harold Burstein from Dana-Farber Cancer Institute, Dr. Angela DeMichele from the University of Pennsylvania, and Dr. Lynn Henry from the University of Michigan, co-chairs on “Endocrine and Targeted Therapy for Hormone Receptor-Positive, HER2-Negative Metastatic Breast Cancer: Capivasertib–Fulvestrant: ASCO Rapid Guideline Update.” Thank you for being here, Dr. Burstein, Dr. DeMichele, and Dr. Henry.

Dr. Harold Burstein: We're happy 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 our guests on this episode today, are available online with the publication of the guideline update in the Journal of Clinical Oncology, which is linked in the show notes. 

So then, to kick us off, Dr. Burstein, could you first describe what prompted this rapid update, which provides updated recommendations for two ASCO guidelines: the biomarkers for systemic therapy in metastatic breast cancer guideline, and the endocrine treatment and targeted therapy for hormone receptor-positive, HER2-negative metastatic breast cancer guideline?

Dr. Harold Burstein: Thanks, Brittany. Well, this team has been working, as you mentioned, actually, on two guidelines, which are clearly evolving in parallel and kind of converging, actually, when you look at data, as we'll be talking about in the next few minutes. The particular catalyst here was a large randomized clinical trial which looked at a new targeted therapy in the space of estrogen receptor-positive, HER2-negative breast cancer. That drug is capivasertib. And the trial was the so-called CAPItello study. In that trial, patients who were receiving second-line therapy with fulvestrant were randomized to that treatment alone, or that plus capivasertib. So the data from that study were the first strong signal that we needed to update the guideline because they were important clinical data.  

The other strong signal was that the drug was tested in a cohort of patients who had a specific set of mutations in their cancers. And that included PIK3CA mutations, a class of mutations for which we already had a targeted drug. But it also included some new potential targets, including mutations in the AKT gene itself, capivasertib is an AKT inhibitor, as well as loss of PTEN protein functionality, which potentially sensitizes tumors to the targeted action of this drug as well. So while we had a couple of guidelines catching up on the endocrine therapy space, which is increasingly looking like a targeted therapy space, it was clear that this major study, which had clinical and diagnostic implications, would sort of push them together and served as the impetus for updating both guidelines at the same time.

Brittany Harvey: Understood. I appreciate that background information.  

So then, Dr. DeMichele, based on this updated data that Dr. Burstein just described, what is the updated recommendation from the guideline panel regarding lines of endocrine treatment?

Dr. Angela DeMichele: Well, I think this is where the biomarker evolution that Dr. Burstein just referred to really comes in because now we have the opportunity to perform genomic testing in patients who have ER-positive, HER2-negative metastatic breast cancer, on either the tumor or commonly from the blood. And we can now start to tailor treatment to the specific genomic abnormalities that that patient's tumor contains. So now our guideline really marries both the genomic abnormality with the therapeutic option. First-line treatment remains endocrine therapy plus a CDK 4/6 inhibitor. But things then really start to diverge once we enter second and third-line therapy because at that point, we now have the option to test for several genomic markers: ESR1 mutations, PIK3CA mutations, AKT1 mutations, and PTEN inactivation. And based on whether the tumor has one or any of those mutations, we can then select the therapy based on that. 

So in the case of capivasertib, as you just heard, that is a therapy for patients whose tumors have PIK3CA mutations or activating mutations in AKT1 or loss of PTEN. But other patients who don't have one of those mutations may, in the second line, go on to another drug. For example, if they have an ESR1 mutation, they then may be eligible to take elacestrant. Patients who have no targetable mutations still have a targeted option in that they can use everolimus. And in all of these settings, the endocrine therapy partner for this line of therapy is typically fulvestrant. So now we're really starting to tailor therapy in the second- and third-line based on genomic changes.

Brittany Harvey: Excellent. That information is helpful for choosing optimal therapy tailored to the individual patients, as you just described. 

So then, Dr. Henry, what guidance does the expert panel provide regarding choosing a PIK3CA targeted option?

Dr. Lynn Henry: Thank you. So for patients whose tumors are found to have an activating mutation in PIK3CA, we now have two drug options: either alpelisib or capivasertib in combination with fulvestrant. And the problem is, these drugs have not been compared head-to-head. We can't say that one is clearly better than the other, either in terms of efficacy or in terms of side effect profile. What we do have is information from two separate trials in which they were each tested against placebo. The efficacy appears to be fairly similar based on the data that we have. It does appear that the side effect profiles may be slightly different. And so, when you have a patient sitting in front of you and you're trying to decide how best to treat her, you really have to think about, what symptoms does my patient already have? What is she more or less likely to tolerate? So what we do know is that it appears that the rates of grade 3 diarrhea and rash were slightly higher with capivasertib. It looks like hyperglycemia was higher with alpelisib, as was treatment discontinuation. So really you have to make an individualized decision when you have a patient sitting in front of you about which drug you'd like to try. Of course, if someone doesn't tolerate one drug, you can always switch to the other one. 

Brittany Harvey: I appreciate that analysis and to provide guidance without a head-to-head trial and to specifically provide options based on an individual patient's profile.  

So then, Dr. DeMichele, what should clinicians know as they implement these new recommendations? 

Dr. Angela DeMichele: Well, first of all, I think most clinicians now are becoming more familiar with the procedures required for doing genomic testing. But this is something that now has become the standard of care. And so, it is incumbent upon all of us who treat these patients to understand what the options for genomic testing are for that patient, which companies offer this testing, how to send a sample, and how to interpret the report that comes back. So, I think this has really added a level of complexity to the therapy for patients. I also think that one can’t simply apply an algorithm to a patient. We have to really treat the whole patient and we have to take into consideration, as Dr. Henry said, the toxicities of these agents and the cost which is also a major issue. So I think that while it is more complex, really that doctor-patient relationship is so important in communicating what these genomic tests mean for a patient and for their options, and also important for the clinician to really understand what the different therapeutic agents might mean for a patient, and really try to pick the agent that’s best for that patient. Using genomic testing is just one of several different features that they’ll consider.

Brittany Harvey: Absolutely. It’s key to obtain the data needed to select appropriate patients and to recognize the complexity.  

So then, Dr. Henry, in your view, how will this update impact patients with metastatic breast cancer?

Dr. Lynn Henry: Yes, so as we’ve discussed, I think this is really exciting. Over the last few years, we have had quite a number of new medications that have become available for patients and have been FDA-approved. And so this is yet the latest in a series. For those patients whose tumors have a PIK3CA mutation, as we discussed, there are now two options. So you have a choice depending on which one is better covered by insurance, by which one you may tolerate better. But I think the other thing is now, although it’s a smaller subset of patients, there are patients out there whose tumors have mutations in AKT1 or alterations in PTEN, and so there’s an entirely new endocrine therapy-based option available for them that wasn’t available before. So I think that thinking about the new data that are out there, the new drugs that are out there, really is exciting because there are new options available and hopefully there are more to come as well.   

Brittany Harvey: Absolutely. It's great to have these new options. 

So, finally, Dr. Burstein, Dr. Henry just mentioned what's to come. Could you touch on what some of the outstanding questions are regarding endocrine therapy for patients with metastatic breast cancer? 

Dr. Harold Burstein: A couple of things to say. First, ER-positive metastatic breast cancer is the most common kind of metastatic breast cancer, roughly three quarters of metastatic cases of breast cancer will be hormone receptor-positive cancers. So this is a very big public health issue around the world, actually, breast cancer being the number one most commonly diagnosed cancer of women around the world. So minor or major improvements in treatment for advanced ER-positive breast cancer really have a tremendous impact. 

The second thing is it’s been remarkable to see the progress in the past decade. We’ve gone from simply targeting the hormonal access itself with medicines like tamoxifen or aromatase inhibitors or an injectable selective estrogen receptor degrader like fulvestrant to incorporating targeted therapies at the same time. And this whole class of drugs called CDK4/6 inhibitors has emerged which we use in either first- or in second-line therapy. Those drugs have transformed our standard of care, improved survival for patients with advanced ER-positive disease, now with median survival nearly 50% longer than what we had seen in the past.  And if you’ve heard, we have a wealth of opportunities. We can target PIK3CA, we can target ESR1 mutations. Other drugs emerging in the space include PROTACs which is another way of degrading the estrogen receptor. And so there’s going to be more progress in the years to come.  

So one of the biggest challenges has been to try and understand, is there really an optimal way to use these drugs, or can we be smarter about the particular sequence of all these particular things that are happening.  So one example of this was a recent study that is on a drug, not as yet FDA-approved, called inavolisib, which is a PIK3CA targeted drug used in first line in combination with a CDK4/6 inhibitor and endocrine therapy. And that study, for a high-risk group of women with ER-positive metastatic disease, actually showed a dramatic improvement in overall survival, asking the question if combining some of these targeted therapies together might yet further improve outcomes. 

And as you’ve heard from the diagnostic space, one of the other interesting things is that tumors evolve over time. And so acquisition of the estrogen receptor mutations, ESR1 mutations, which are typically not found early in the course of advanced breast cancer but otherwise later, now have targeted treatments. So there’s a whole bunch of stuff going on all at the same time, including multiple ways of targeting things, serial testing to look for acquisition of ESR1 mutations and new pathways to explore. It’s an embarrassment of riches in some respects because it has meant it’s actually really hard to write a guideline as you’ve heard, which says, “Do this first, do this second, and do this third.” I suppose that’s a good problem to have under the circumstances, but it’s going to require really thoughtful clinical trials and careful analysis to help guide specific lines of treatment recommendations like that. 

Brittany Harvey: Excellent. We’ll look forward to these exciting, continuing developments for patients with metastatic breast cancer. And I want to thank you all so much for your work to develop this rapid recommendation update for these two guidelines. And thank you for taking the time on this podcast today.

Dr. Harold Burstein: Thanks.

Dr. Lynn Henry: Thank you so much. 

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 heard today, please rate and review the podcast and be sure to subscribe so you never miss an episode.

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