ASCO: You’re listening to a podcast from Cancer.Net. This cancer information website is produced by the American Society of Clinical Oncology, known as ASCO, the world’s leading professional organization for doctors who care for people with cancer. The purpose of this podcast is to educate and to inform. This is not a substitute for professional medical care and is not intended for use in the diagnosis or treatment of individual conditions. Guests on this podcast express their own opinions, experience, and conclusions. Guests statements on this podcast do not express the opinion of ASCO. The mention of any product, service, organization, activity, or therapy should not be construed as an ASCO endorsement. Cancer research discussed in this podcast is ongoing, so the data described here may change as research progresses. 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