Research Highlights from the 2020 San Antonio Breast Cancer Symposium, with Norah Lynn Henry, MD, PhD, FASCO

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. 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 discusses new research presented at the 2020 San Antonio Breast Cancer Symposium, held virtually December eighth through eleventh. 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. View Dr. Henry’s disclosures at Cancer.Net. ASCO would like to thank Dr. Henry for discussing this research. 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 2020 virtual San Antonio Breast Cancer Symposium. My institution enrolled patients in the first trial that I will discuss, otherwise, I have no conflicts of interest for any of the trials that I will talk about. Today, I'm going to focus primarily on treatment of non-metastatic breast cancers that are hormone receptor-positive and HER2-negative. These studies highlight personalizing treatment for individual patients. In the first and last trials I will mention, the studies examine whether it is possible to give less treatment without substantially increasing the risk of breast cancer recurrence. In general, giving less treatment leads to fewer long-term toxicities and better quality of life. In contrast, the other 2 trials I will mention are examining adding more therapy to standard treatment with the goal of increasing breast cancer cure rates for patients at high risk of recurrence without causing too much additional toxicity. One of the biggest stories in this meeting was the result of the RxPONDER trial. This trial enrolled thousands of women with hormone receptor-positive, HER2-negative breast cancer, who had cancer present in 1 to 3 lymph nodes under her arm. The standard treatment for patients who have lymph node positive breast cancer has been to recommend chemotherapy in addition to anti-hormone therapy. This trial is testing whether that is actually the best treatment. In this trial, every patient's tumor was tested with a test called Oncotype DX and was given a recurrence score ranging from 0 to 100, depending on how quiet or aggressive the tumor is. Women whose tumors had a score between 0 and 25, which is at the low range, were randomized, like flipping a coin, to either receiving the standard, which is chemotherapy followed by anti-hormone therapy, or to just anti-hormone therapy alone. The patients were then monitored to see if they developed recurrence of their breast cancer. Overall, there was no difference between the groups. Meaning that adding chemotherapy to the treatment did not provide a benefit in terms of reducing risk of recurrence. When they divided the groups by lower or higher score, it still didn't make a difference. However, when they divided the women by menopausal status, it did. Women who were post-menopausal when they were diagnosed with breast cancer did not get any benefit from chemotherapy. In contrast, women who were pre-menopausal did get a benefit from chemotherapy. And in fact, they lived a little longer than those who only got anti-hormone therapy. However, there's still a question about how much of the benefit is from the chemotherapy itself acting directly on the cancer and how much is from the chemotherapy putting the ovaries to sleep, which also treats the cancer, although indirectly. Therefore, the take-home message for a post-menopausal woman with hormone receptor positive, HER2-negative breast cancer who has 1 to 3 involved lymph nodes, is to talk with her oncologist about whether her tumor should be tested to help make a decision about chemotherapy as opposed to just assuming that she needs chemotherapy because her lymph nodes have cancer in them. For pre-menopausal women, it's a little less clear, unfortunately. In that case, it is important to talk about the pros and cons of chemotherapy with her oncologist depending on her exact situation, including her age and the amount of cancer in the breasts and the lymph nodes. Hopefully, we will learn more about how best to treat pre-menopausal women when additional analyses are performed on the data from this trial. Also related to non-metastatic hormone receptor positive, HER2-negative breast cancer, updates on 2 trials related to the use of adjuvant CDK4/6 inhibitors on patients with high risk to breast cancer recurrence were presented. The CDK4/6 inhibitor medicines are routinely used to treat patients with metastatic breast cancer since the combination of these drugs plus anti-hormone therapy results in longer time to disease worsening compared to just anti-hormone therapy alone. Therefore, these drugs are now being tested in the non-metastatic setting to see if they increase the likelihood of cure of breast cancer. In the first trial called MonarchE, addition of abemaciclib, which is a CDK4/6 inhibitor, to standard aromatase inhibitor therapy decreased the likelihood of recurrence of invasive disease in patients at high risk of disease recurrence. However, the length of follow up of the patients who participated in the trial is still rather short, and so far, adding the treatment has not shown that people will actually live longer. The other trial that was presented, called PENELOPE-B, studied a similar CDK4/6 inhibitor medicine called palbociclib in a similar setting. In that trial, although the benefits looked promising early on, with longer follow up, the benefits have unfortunately disappeared. Therefore, although the results of MonarchE look very promising, we still need more follow up to determine the actual benefit to patients. Also importantly, this drug is not currently approved for treatment of early stage breast cancer at high risk of recurrence, and it is not currently included in treatment guidelines. So at this point, it is unlikely that the drug costs will be covered. We await additional updates from these and other trials of similar design in order to know whether patients should be receiving these drugs as part of their breast cancer treatment. And finally, to change gears a little to patients who are at low likelihood of disease recurrence, we also got an update of the PRIME II trial. This trial asked whether radiation therapy is beneficial in women over the age of 65 who have small lymph node-negative, hormone receptor-positive breast cancer. In this trial, most patients had tumors that were smaller than 2 centimeters, and all underwent lumpectomy and were planning to take adjuvant anti-hormone therapy. Patients were randomized either to receive radiation therapy or to not receive radiation therapy. Radiation therapy is the standard of care in this setting. Consistent with their earlier results, not having radiation therapy did increase the risk of local recurrence a little from 1% to 10% over 10 years. And this really highlights that although the risk of local recurrence in the breast is a bit higher if a patient does not have radiation therapy, it still has a 90% chance of not having a recurrence during that 10-year period. Also, not getting radiation did not affect survival from breast cancer. It is important to note that most patients likely took endocrine therapy, and it is thought that risk of recurrence is higher if both radiation therapy and endocrine therapy are omitted. Therefore, patients over the age of 65 or 70 who have small hormone receptor-positive breast cancers should talk with their surgeon, medical oncologist, and radiation oncologist about the benefits and risks of radiation and make a personal decision about whether or not to undergo radiation therapy. Well, that's it for this quick summary of this important research from the 2020 virtual San Antonio Breast Cancer Symposium. Overall, we continue on a fast track in breast cancer with many new and exciting therapies being actively studied and research helping support our patients do better than ever before. 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. You can find all 9 shows, including this one, at podcast.asco.org. Cancer.Net is supported by Conquer Cancer, the ASCO Foundation, which funds breakthrough research for every type of cancer, helping patients everywhere. To help fund Cancer.Net and programs like it, donate at conquer.org/donate.