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Highlights From ESMO 2023

Scientists and doctors from around the world recently gathered for the 2023 European Society for Medical Oncology (ESMO) Congress, which took place Oct. 20-24 in Madrid, Spain. Here, researchers present their latest findings that have the potential to change the standard of care for patients here in the United States. This year’s meeting was full of exciting news for breast cancer. 

New Approaches and Questions Raised for ER-positive Breast Cancer 

Immunotherapy, which kickstarts the immune system to help fight cancer, has shown some success in triple negative breast cancer, but its use in treating other types of breast cancer has been unclear. For the first time, results from two Phase 3 trials presented at ESMO, the KEYNOTE-756 and CheckMate-7FL trials, found patients with high-risk, early estrogen receptor-positive (ER-positive) breast cancer, may also benefit from immunotherapy drugs.  

In both trials, patients were given immunotherapy drugs (pembrolizumab or nivolumab) in combination with chemotherapy prior to surgery, then continued immunotherapy in combination with hormone therapy following surgery. Compared to those who received a placebo, those who were given immunotherapy were more likely to achieve a pathologic complete response, meaning they had no evidence of cancer remaining in their breast. These are promising results, but longer follow-up will be needed to determine whether these treatments reduce the risk of cancer coming back, which is known as a recurrence.  

Updated results were presented for two other trials that focused on preventing recurrence in early ER-positive breast cancer. Updates from the monarchE and NATALEE trials showed the CDK4/6 inhibitors abemecicilb or ribociclib, given in combination with hormone therapy after surgery, continued to improve outcomes for patients.  

Given the success of these treatment approaches and new drug options potentially on the horizon for early ER-positive breast cancer, doctors will need to determine which approach is the right fit for each patient. New tools and biomarkers will be needed to determine the best course of treatment for each individual tumor. 

New Drugs for ER-positive Breast Cancer 

In addition to new treatment approaches, researchers also shared exciting results for new drugs being tested to treat ER-positive breast cancer. Former Komen grantee Aditya Bardia, M.D., shared positive results from the Phase 3 TROPION-Breast01 trial. This trial tested whether the TROP-2 targeting antibody-drug conjugate, datopotamab deruxtecan (Dato-DXd), could delay cancer progression more effectively than chemotherapy in metastatic ER-positive breast cancer. The results showed Dato-DXd delayed time to progression by two months when compared to chemotherapy. Another exciting finding was that patients receiving Dato-DXd had less than half the number of severe side effects compared to those receiving chemotherapy. Pending FDA approval, this drug could mean a better quality of life for these patients. 

Komen Scholar Nancy Lin, M.D., presented Phase 2 trial results evaluating a new hormone therapy called palazestrant for metastatic ER-positive breast cancer. The study found that patients taking palazestrant alone continued for a median of 5.6 months without disease progression. Based on these promising results, a Phase 3 clinical trial will be starting soon to test palazestrant against the current standard of care for second or third-line treatment of metastatic ER-positive breast cancer. 

Fighting Hidden Cancer Cells 

Dormant cancer cells can lead to breast cancer recurrence. Dormant cancer cells are cells that did not die from a person’s initial treatment. These cells can lie in wait, undetected, until they begin to grow again and form new tumors, sometimes years or even decades later.  

Komen Scholar Angela DeMichele, M.D., MSCE, presented results from the Phase 2 CLEVER trial, which tested whether it’s possible to find and eliminate dormant cancer cells before they cause a recurrence. Using FDA-approved drugs hydroxychloroquine and everolimus, the researchers found they could remove dormant cancer cells from about 80% of patients who completed their cancer treatment within five years from the time of enrollment. This meant that only two out of 51 patients in the study experienced a recurrence after two years of follow-up. While CLEVER and several other trials are ongoing to confirm these results, these findings have already proven to be an important step forward in preventing disease recurrence. 

These updates from ESMO 2023 represent exciting advancements for the future of breast cancer research. Additional updates on some of these clinical trials will be announced at the 2023 San Antonio Breast Cancer Symposium (SABCS). The December episode of Breast Cancer Breakthroughs will be focused on the biggest news coming out of SABCS; click on the link to sign up for updates.