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In this podcast, Cancer.Net Associate Editor Dr. Norah Lynn Henry covers new research in breast cancer treatment, prevention, and survivorship presented at the 2022 San Antonio Breast Cancer Symposium, held December 6-10.

Dr. Henry is a Professor and Interim Chief of the University of Michigan's Division of Hematology/Oncology in the Department of Internal Medicine and is the Breast Oncology Disease Lead at the Rogel Cancer Center in Ann Arbor, Michigan.

View Dr. Henry’s disclosures at Cancer.Net.

Dr. Henry: Hi, I'm Dr. Lynn Henry, a breast cancer oncologist from the University of Michigan Rogel Cancer Center. Welcome to this quick summary of updates from the 2022 San Antonio Breast Cancer Symposium. I have no conflicts of interest for any of the trials that I will talk about today. First, I'm going to give a very brief overview of the types of breast cancer, and then talk about some research that was presented on both metastatic and early-stage breast cancer. As a reminder, there are multiple kinds of breast cancer. Some breast cancers are called hormone receptor-positive or estrogen receptor-positive and are stimulated to grow by the hormone estrogen. We treat those cancers with anti-estrogen treatments, which block estrogen or lower estrogen levels. We often combine anti-estrogen treatments with other medications to try to make them work even better against the cancer. Other breast cancers are called HER2-positive. These are often more aggressive cancers, but because they have extra copies of HER2, they often respond to treatments that block HER2. Finally, there are breast cancers that don't have hormone receptors or HER2 receptors. These are called triple-negative breast cancer and are also often fairly aggressive cancers.

One of the most exciting takeaways from the San Antonio meeting was the promise of new medications on the horizon to treat hormone receptor-positive, HER2-negative metastatic breast cancer. A commonly used treatment for metastatic breast cancer that is hormone receptor-positive and HER2-negative is fulvestrant, which is a type of medicine called “SERD,” or selective estrogen receptor degrader. At the meeting, we heard new data about 2 new SERD medications: elacestrant that was tested in the EMERALD trial and camizestrant that was tested in the SERENA trial, both of which are oral pills instead of injection medications and both of which may work particularly well against tumors that have mutations in the estrogen receptor called ESR1. In addition, we heard about capivasertib, which is an AKT inhibitor that was shown to work well when combined with fulvestrant and had less toxicity than some of the similar drugs that had previously been tested.

For treatment of HER2-positive metastatic breast cancer, there are now a lot of medications that have been FDA approved, so some of the questions that clinical trials are now examining are related to what order we should use the medications in when we are treating patients. We heard about 2 studies of the medication trastuzumab deruxtecan, which I'm going to refer to as Enhertu. This drug is a combination of the anti-HER2 antibody trastuzumab plus a chemotherapy drug, and the antibody targets the drug to a cancer like a guided missile. Enhertu is currently routinely used to treat patients with metastatic HER2-positive breast cancer. We heard updated data that showed that when Enhertu was compared head-to-head against trastuzumab emtansine, also known as Kadcyla, patients who were treated with Enhertu were able to stay on the medication for a lot longer compared to patients who were treated with Kadcyla. We also heard that for patients who had already been treated with Kadcyla but it was no longer working, it is reasonable to switch to treatment with Enhertu at that point, because it is still likely to be effective. These studies may help oncologists decide what order to use these newer medications when treating patients with HER2-positive breast cancer.

To switch gears a little bit, I'll now talk about another study I found interesting. This one is in the setting of people who are at high risk of developing breast cancer, but who haven't actually been diagnosed with cancer yet. In general, people are recommended to take either tamoxifen or an aromatase inhibitor medication, which is the same as treatment for patients who have been diagnosed with hormone receptor-positive breast cancer. But in this case, it's trying to prevent them from ever getting breast cancer in the first place. However, many people don't take the medications because they are concerned about side effects. A study was therefore performed in Italy that compared the 5-milligram dose of tamoxifen, which is only one-quarter of the full dose, with placebo for 3 years. After 7 years of follow-up, this low dose of tamoxifen, which is being referred to as “babytam,” was shown to reduce the risk of developing breast cancer by about half, which is similar to the effects seen with the full dose of the medication. Plus, there were fewer side effects. This lower dose is likely to be used regularly for prevention of breast cancer based on these findings, although this lower dose of tamoxifen has not yet been tested to see if it is as effective as the full dose of medication for preventing breast cancer recurrence, so it is not routinely recommended for patients who have a diagnosis of breast cancer to receive this lower dose.

Finally, I will touch briefly on exciting results from the POSITIVE trial, which is a trial conducted around the world that examined whether it is safe for young women with hormone receptor-positive breast cancer to stop taking anti-hormone therapy to become pregnant. The women on this trial stopped taking endocrine therapy after taking it for about 18 to 30 months, and then spent up to 2 years trying to become pregnant. About three-quarters of the patients had at least 1 pregnancy during that time, and importantly, there was no increased risk of breast cancer recurrence seen in these patients. Once patients were done with their pregnancy, it was recommended that they restart taking endocrine therapy again.

There were a lot of other research findings presented that were related to treatment for both early-stage and metastatic breast cancer at this meeting. Importantly, we got glimpses of the many new drugs on the horizon for treatment of breast cancer, including the 3 that I mentioned already. And we eagerly await the results of large, randomized trials so that the drugs that work can be used to care for patients with breast cancer. But for now, that's it for this quick summary of important research from the 2022 San Antonio Breast Cancer Symposium. Stay tuned to Cancer.Net for future updates from upcoming breast cancer conferences. Thank you.

ASCO: Thank you, Dr. Henry. You can find more research from recent scientific meetings at www.cancer.net.

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