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Heather L. McArthur, MD, MPH

UT Southwestern Medical Center
Dallas, Texas

Titles and Affiliations

Associate Professor in the Department of Internal Medicine
Komen Distinguished Chair in Clinical Breast Cancer Research
Clinical Director, Breast Cancer Program,
Harold C. Simmons Comprehensive Cancer Center

Research area

Testing a new immunotherapy and radiation strategy to reduce toxicity and improve outcomes in triple-negative breast cancer.


Triple-negative breast cancer (TNBC) is a highly aggressive subtype of breast cancer characterized by early recurrence and high mortality. While chemotherapy remains the backbone of therapy in these patients, the addition of immunotherapy, such as pembrolizumab has led to substantial improvements in clinical outcomes for some patients. However, the approved regimen requires four chemotherapy drugs in combination with pembrolizumab, thereby resulting in intense side effects for patients. Furthermore, among the 37 percent of patients who do not achieve a pathological complete response (pCR) with pembrolizumab and chemotherapy, approximately one-third will experience a distant recurrence (metastasis). Dr. McArthur and her team are testing a new strategy with the aim of reducing toxicity and improving outcomes.

Progress Thus Far

The team recently completed a preliminary study in the neoadjuvant (pre-operative) setting in which patients with early stage TNBC received radiation in combination with pembrolizumab prior to chemotherapy. The treatment was followed by surgery. Dr. McArthur’s team reported that 56 percent of patients had no evidence of disease at the tumor site at the time of surgery in spite of reduced doses of both pembrolizumab and chemotherapy compared to the current standard-of-care regimen.

What’s next

After establishing that radiation could synergize with immunotherapy and administered safely in the pre-operative setting, the team will perform a randomized phase 2 trial to test the pembrolizumab-chemotherapy combination with or without radiation prior to surgery. This study has the potential to lead to a new breakthrough in the treatment of patients with high-risk, localized TNBC.


Heather McArthur, MD, MPH joined UT Southwestern Medical Center in 2021 as the Komen Distinguished Chair in Clinical Breast Cancer Research. She is a medical oncologist with a clinical practice dedicated to the care of patients with breast cancer. Her research activities are focused on innovations in the diagnosis and treatment of breast cancer, with a particular interest in novel immune therapy strategies. Dr. McArthur completed formal medical oncology training at the University of British Columbia. There, she was awarded the highly competitive Canadian Association of Medical Oncology/Canadian Institute for Health Research R&D Fellowship which funded an advanced clinical research fellowship at MSKCC. Thereafter, she joined MSKCC as faculty and in that role developed the institutional breast cancer immunotherapy program before joining Cedars-Sinai in 2016. She has a Master’s in Public Health with a focus on clinical trial design from Harvard University and has mentored many medical students, residents, fellows, and junior faculty in the conduct and reporting of several studies – two of which directly informed national (NCCN) treatment guidelines.

Dr. McArthur has designed, conducted, and reported on many studies in breast cancer and has held several leadership positions in the field including US Co-Chair of a Breast International Group Immunotherapy Taskforce, member of an NCI Breast Cancer Immuno-Oncology (IO) Working Group, member of a NCI Breast Cancer IO Task Force, and member of the Alliance for Clinical Trials in Oncology Immunotherapy/Immune Monitoring Working Group. She has served on the ASCO Conquer Cancer Foundation YIA/CDA Grant Selection Committee, the ASCO Breast Cancer Symposium Program Committee, and as a faculty member for the ASCO Annual Meeting Grant Writing Workshop. She is currently on the ASCO Annual Meeting IO Scientific Committee and participates in the ASCO Leadership Development Program. She has served as a reviewer for numerous journals including Science, the New England Journal of Medicine, and Cancer, and has authored more than 70 articles, review articles, invited commentaries, and book chapters on breast cancer.

BCRF Investigator Since


Areas of Focus