Immunotherapy has revolutionized the treatment paradigm of many cancers. Although immune checkpoint inhibitor-based treatment is currently the cornerstone of treatment for certain subtypes of breast cancer, especially triple-negative breast cancer (TNBC), clinical benefit is not uniform nor universal across all patients. Biomarkers predictive of response to immunotherapy are pivotal to optimal patient selection and improved outcomes.

At the 2024 San Antonio Breast Cancer Symposium®, presenters will provide perspective on this current landscape during State of the Art Session 1: The Winding Road of Immune Biomarkers in Early Breast Cancer, on Wednesday, December 11, from 2 to 3 p.m. CT in Stars at Night Ballroom 3-4 at the Henry B. Gonzalez Convention Center.

The topic of immune biomarkers in the early-stage setting is particularly relevant at this time, said session moderator Sherene Loi, MBBS (Hons), PhD, FRACP, FAHMS, GAICD, Professor of Cancer Therapeutics and Head of the Translational Breast Cancer Genomics and Therapeutics Lab, Peter MacCallum Cancer Centre at the University of Melbourne, and Co-Chair of the International Immuno-Oncology Biomarkers Working Group.

“Firstly, we have seen this year that pembrolizumab increases overall survival when incorporated into the neoadjuvant regimen for early-stage TNBC patients. This is a critical milestone given the dismal survival of those with recurrent disease,” Dr. Loi said. “Secondly, we have developed, standardized, and collated a large body of evidence on simple immune biomarkers evaluated on H&E-stained diagnostic slides, looking at the extent of immune infiltration. This biomarker has a large body of clinical evidence on its prognostic and predictive relevance and is now recognized by international bodies such as the WHO and U.S. FDA.”

During the session, Roberto Salgado, MD, PhD, Honorary Research Associate at the Division of Research, Peter MacCallum Cancer Center, and Co-Chair of the International Immuno-Oncology Biomarkers Working Group, will provide an update on tumor-infiltrating lymphocytes (TILs) after 10 years of research. TILs are an important prognostic biomarker in breast cancer, especially in TNBC, wherein TILs can inform up/downstaging of tumors staged according to the traditional pathologic American Joint Committee on Cancer (AJCC) staging system, Dr. Loi said.

Justin Balko, PharmD, PhD, Professor of Medicine (Hematology/Oncology) and Co-Leader of the Breast Cancer Research Program at Vanderbilt-Ingram Cancer Center, will explore other immune biomarkers that can also impact clinical management of TNBC, such as expression of the checkpoint regulator programmed death ligand 1 (PD-L1), presence of high tumor mutation burden or high microsatellite instability, and alterations impacting the mismatch repair system.

Biomarkers predictive of response to immunotherapy can not only help individualize immunotherapy strategies but also preclude unnecessary treatment-related toxicities in non-responders, Dr. Loi said. To this end, there is a continued need for discovery and validation of immune biomarkers in clinical trials. Priyanka Sharma, MD, Professor of Medicine at the University of Kansas Medical Center, will address that topic during the session.

“This session will discuss how immune biomarkers can help us better optimize and tailor treatment for our breast cancer patients,” Dr. Loi said. “This is particularly relevant for better understanding PD-L1 assays and treatment of patients with advanced TNBC. PD-L1 assays have significant limitations, and it is important for physicians to understand those limitations, so patients do not miss out on life-saving treatments.”

Anyone who treats breast cancer patients and prescribes immunotherapy — including physicians, surgeons, and pathologists — should attend the session, Dr. Loi said, especially given the important and expanding role immunotherapy will play in breast cancer treatment in the future.