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Top Research Presented at the 2021 San Antonio Breast Cancer Symposium
Sara Tolaney, MD, MPH
December 21, 2021

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Sara tolaney

Dr. Sara Tolaney is chief of the Division of Breast Oncology and associate director of the Susan F. Smith Center for Women’s Cancers at the Dana-Farber Cancer Institute, as well as associate professor of medicine at Harvard Medical School.

The 2021 San Antonio Breast Cancer Symposium featured four days of presentations on the latest research on breast cancer. Dr. Tolaney joined us to discuss the research that is most immediately applicable to people who’ve been diagnosed with the disease.

Listen to the episode to hear Dr. Tolaney explain:

  • results of an early study looking at how effective the experimental medicine datopotamab deruxtecan was in treating metastatic, triple-negative breast cancer
  • a study comparing Enhertu (chemical name: fam-trastuzumab-deruxtecan-nxki) to Kadcyla (chemical name: T-DM1 or ad-trastuzumab emtansine) for metastatic, HER2-positive breast cancer that had spread to the brain
  • the studies that she thinks are practice-changing

Running time: 10:00

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Jamie DePolo: Hello. Thanks for listening. Dr. Sara Tolaney is chief of the Division of Breast Oncology and associate director of the Susan F. Smith Center for Women’s Cancers at the Dana-Farber Cancer Institute as well as associate professor of medicine at Harvard Medical School.

The 2021 San Antonio Breast Cancer Symposium featured four days of presentations on the latest research on breast cancer. Dr. Tolaney joins us to discuss the research that is most immediately applicable to people who’ve been diagnosed with the disease.

Dr. Tolaney, welcome to the podcast.

Dr. Sara Tolaney: Oh, thanks so much for having me.

Jamie DePolo: So far, I’ve talked to Dr. Bardia, who presented the results of the EMERALD study on elacestrant, and to Dr. Braybrooke, who did the meta-analysis on studies comparing aromatase inhibitors and ovarian suppression to tamoxifen in premenopausal women. What other studies at this year’s conference stood out for you?

Dr. Sara Tolaney: I think it was a very exciting meeting with lots of very good data that came out. One study that I think is particularly exciting focused on a new drug, called datopotamab deruxtecan, which we called Dato-DXd for short. This is a type of drug that we call an antibody-drug conjugate, meaning that it’s really taking the antibodies that’s targeting something on the cancer cell surface, and delivering a very potent chemotherapy into the cancer cell. And this drug, Dato-DXd, was studied in a clinical trial of patients with metastatic, triple-negative breast cancer. And what they found was that there were many patients who had significant reduction in their tumor. So, in fact, almost 80 percent of patients treated with the drug had tumor shrinkage, and a little over 30 percent of patients in the trial had significant amounts of tumor shrinkage. And, so this was really exciting because these were patients who had seen other treatments before but are having really robust benefits in terms of their cancer.

And I think the other important thing is the drug was, generally speaking, pretty well-tolerated. The major side effect with it was mouth sores. But it didn’t actually cause many side effects that we typically see with chemotherapy, such as having low blood counts and developing infection from them. So I think, generally speaking, it’s a very exciting new drug that is getting moved forward into multiple trials over the coming several months, and so I think it will be nice to see more from this drug.

I think another really exciting piece of data that came out, came out of a study looking at another antibody-drug conjugate called trastuzumab deruxtecan, or TDxD. This drug was studied in metastatic, HER2-positive breast cancer, and it was compared to another typical drug that we give to metastatic, HER2-positive disease called T-DM1.

Then, I think why this study is so remarkable is that when patients were randomized to either get this new drug, TDxD, or to get a more standard treatment, T-DM1, the people who got the new drug, TDxD, did dramatically better, and their disease was controlled significantly longer. In fact, almost four times as long, the treatment lasted, compared to the standard T-DM1.

But, what we saw at this year’s San Antonio Breast Cancer Conference was that patients who got TDxD not only had their disease controlled longer, but when they looked at those patients who actually had brain metastases, when they went on to the study, these were stable brain metastases. They, in fact, saw that the tumors in the brain shrunk and that many of these people had significant shrinkage of their cancer in the brain. And this is really exciting because many of us were worried that these types of drugs, these antibody-drug conjugates, may not penetrate into the brain because they’re really big molecules, and we weren’t sure if they could get in through the blood-brain barrier and actually shrink brain metastases, but we see that it does. So I think, really, again, exciting data and there were actually several other presentations at the meeting also supporting activity of this drug, TDxD, in the brain.

So, again, lots, lots of real exciting things that came out at the meeting, which was nice to see.

Jamie DePolo: That’s great. Now, in your opinion, are these studies practice-changing? It sounds like they may be, but sometimes the studies that get presented are phase I or phase II, and it’s — it certainly is very exciting. I don’t mean to take away from that — but, then it can be several years before the new drugs may be approved, and then available to patients. So, what’s your opinion on how soon we’re going to see some of these actually in, you know, my local cancer treatment center?

Dr. Sara Tolaney: Well, and a very good question. So I think the data that you heard about earlier about elacestrant — one of the new oral SERDs — that data, I think, is practice-changing. And we hear that that drug will get submitted to the FDA. And so, hopefully, sometime in 2022, it is possible that that will be a new drug that’s on the shelf that could be accessible to patients. So, hopefully, that will happen, but as you point out, some trials are earlier in development and are not necessarily going to lead to an immediate approval of an agent.

So, for example, a study we talked about looking at Dato-DXd, which looked very promising in triple-negative breast cancer. That data does come from the phase I expansion studies, and not something that would lead to FDA registration at this time. Even though, again, the data are very promising. But that drug will now be studied in larger trials that, hopefully, will lead to a registration in the future, but certainly not in the near-term as more work needs to be done.

The other agent we talked about, TDxD, that agent, actually, is already FDA-approved for metastatic, HER2-positive disease. But the trial was studying it in an earlier line of treatment, and so we’re hoping that these very robust data will also lead to the drug having approval even in earlier lines, compared to its current approval. So, I think that one is more just allowing access to a drug to a larger population of patients. But, I think all these drugs are really moving forward, which is a good thing because it’s nice to be able to get these drugs to patients soon.

Jamie DePolo: Absolutely. Absolutely. And I’m curious, the phase I drug study — I’m going to not remember the name that you called it —

Dr. Sara Tolaney: The Dato-DXd. I know these names are...

Jamie DePolo: That one.

Dr. Sara Tolaney: …really not easy.

Jamie DePolo: Yes. That one. Now, is that given as an infusion? Is that something that somebody would have to go to, say, like, a chemotherapy treatment center to get?

Dr. Sara Tolaney: Yes. The Dato-DXd is given IV every three weeks.

Jamie DePolo: Okay.

Dr. Sara Tolaney: So, you would have to get it at an infusion center every three weeks. But, it’s nice, compared to many of our other IV drugs, the infusion’s only every three weeks, which is certainly better than most other chemos, which are often weekly infusions. So, definitely a better schedule than many other agents.

Jamie DePolo: Okay. Thank you. And I guess, to wrap up: It sounds like, really, the thing that we may see the soonest out of this study — I know Enhertu is already approved, as you mentioned, but this is looking at it in an earlier line. But, it sounds like elacestrant would be the kind of — the biggest news that may have the most immediate applicability for somebody who’s diagnosed as far as a new treatment [that] may be available within the next year?

Dr. Sara Tolaney: Yeah. I think that that’s true. That, of all the agents that was presented in San Antonio, that one is one that isn’t currently approved. And, given the positive data that we saw, there is interest in getting that drug approved, and it will get submitted to the FDA. So, I think you’re right that that one, hopefully, will lead to a new approval. And, in fact, if that’s true, it would actually be the very first oral SERD that, that would be approved in breast cancer. So really, really exciting to see.

Jamie DePolo: That’s great. Dr. Tolaney, thank you so much for your insights. We really appreciate it.

Dr. Sara Tolaney: Oh, no. Thank you very much for having me.

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