Research Highlights from the 2021 San Antonio Breast Cancer Symposium, with Norah Lynn Henry, MD, PhD, FASCO

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In this podcast, Cancer.Net Associate Editor Dr. Norah Lynn Henry will discuss new research presented at the 2021 San Antonio Breast Cancer Symposium, held December 7-10. Dr. Henry is an Associate Professor in 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. I'm here with exciting updates from the leading international breast cancer meeting, the San Antonio Breast Cancer Symposium, that was recently held in San Antonio, Texas, and online. I have no conflicts of interest for any of the trials that I will talk about. First, I'm going to give a very brief overview of the types of breast cancer, then talk about some research that was presented on both metastatic and early- stage breast cancer. Then to wrap it up, I'm going to mention an interesting study looking at lymphedema. 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 antiestrogen treatments, which block estrogen or lower estrogen levels. 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. These are called triple-negative breast cancers and are also often aggressive cancers. So first, I'm going to talk about treatment for HER2-positive metastatic breast cancer. Many of the treatment regimens that we use for treating patients with HER2-positive breast cancer include the antibody trastuzumab, which is also called herceptin. More recently, 2 drugs have been approved that include trastuzumab linked to a chemotherapy drug. So they're sort of like smart drugs. One is called trastuzumab emtansine and the other is called trastuzumab deruxtecan. In the DESTINY-Breast03 trial, which was presented earlier this year, the deruxtecan drug was shown to be more effective than the emtansine one. At this San Antonio meeting, the investigators look specifically at how well these 2 drugs worked in patients whose breast cancer had spread to their brain. And these exciting results, the deruxtecan drug was shown to greatly lengthen the time until cancer worsens compared to the emtansine drug, from 3 months on average to 15 months. In addition, on brain MRI, almost two-thirds of the patients had shrinkage of the brain lesions when they received the deruxtecan drug, compared to only about one-third who received emtansine. These important findings give us yet another potential treatment that we can use to help patients who have HER2-positive breast cancer that has spread to their brains. So next, I'm going to switch gears and talk about treatment of metastatic hormone receptor-positive breast cancer. At this time, the initial treatments are generally with antihormone drugs, such as aromatase inhibitors or fulvestrant. Unfortunately, these drugs often stop working, and then patients have to switch to chemotherapy medication. The good news is, that there are a number of new antihormone drugs currently being developed in the EMERALD trial, which was presented at this meeting. Investigators tested a new antihormone medicine called elacestrant in postmenopausal women with metastatic breast cancer whose cancer had previously worsened during treatment with medicines called CDK4/6 inhibitors plus antihormone treatment. These findings are exciting because this new drug may work against some cancers that no longer respond to a currently available antihormone medicines. It might mean they don't yet need to switch to chemotherapy. However, the findings are still early, and this drug is not yet approved by the FDA. I'm sure we'll hear more about this drug and other similar ones in the months and years to come. There were a lot of other research findings presented related to treatment for early- stage breast cancer at the meeting. And there were quite a number of updates from studies that were previously presented. For example, in patients with stage 2 and 3 triple-negative breast cancer, adding immunotherapy to neoadjuvant chemotherapy, which is chemotherapy given before surgery, improves event-free survival. Similarly, updated results from the RxPONDER clinical trial confirm that it is okay to not to give chemotherapy to postmenopausal women with hormone receptor-positive HER2-negative breast cancer who have 1 to 3 involved lymph nodes, and a 21-gene recurrence score of 25 or less. Finally, there was a report of a large clinical trial examining whether the diabetes drug, metformin, can decrease the risk of breast cancer recurrence, especially in hormone receptor-positive breast cancer. Unfortunately, taking metformin did not lower the risk of breast cancer recurrence compared to placebo. So it is not recommended that patients take this drug specifically to try to lower their risk of breast cancer coming back. In addition to these studies reporting findings about new medications, we also learn new information about an old problem, lymphedema. A group of women were followed over 2two years after they were diagnosed with breast cancer and underwent axillary lymph node dissection or removal of a large number of lymph nodes from under their armpit. Using a specific type of lymphedema measurement that looks at swelling in the arm, they found that almost 1 in 10 patients had developed lymphedema within 1 year of surgery, and almost 1 in 4 had lymphedema within 2 years. These are similar to what other studies had previously found. But importantly, patients who were Black were much more likely to develop lymphedema compared to white or Asian patients. This association with race hadn't been carefully looked at before and suggests that additional studies need to be done to figure out how best to monitor for, prevent, and treat lymphedema in all patients with breast cancer. Importantly, at this meeting, we also got glimpses of the many new drugs on the horizon for the treatment of breast cancer. And we eagerly await the results of large randomized trials so that the drugs at 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 2021 San Antonio Breast Cancer Symposium. Overall, we continue on a fast track in breast cancer with many new and exciting therapies being actively studied, as well as research helping support our patients to do better than ever. 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. And if this podcast was useful, please take a minute to subscribe, rate, and review the show wherever you listen to podcasts. This Cancer.Net podcast is part of the ASCO Podcast Network. This collection of 9 programs offers insight into the world of cancer care, covering a range of educational, inspirational, and scientific content. 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