Expert Directory

Susan O’Brien, MD

Division of Hematology/Oncology
Department of Medicine
University of California, Irvine
Irvine, CA

Susan O'Brien, MD, is the recently retired associate medical director at the Chao Family Comprehensive Cancer Center, University of California, Irvine (UCI), and the recently retired medical director at the Sue and Ralph Stern Center for Cancer Clinical Trials and Research, UCI. She is currently a professor in the Division of Hematology/Oncology, Department of Medicine, UCI. 

Dr O'Brien received her medical degree from and completed her residency in internal medicine at the University of Medicine and Dentistry of New Jersey (currently known as the Rutgers School of Biomedical and Health Sciences). She completed her oncology fellowship at The University of Texas MD Anderson Cancer Center (MD Anderson) and joined the faculty after completion of her fellowship. When she left MD Anderson in 2015, she was the Ashbel Smith Professor of Medicine in the Department of Leukemia.

She is considered a leading worldwide leukemia expert (, with an H index of 170. She is included in the top 1% of the most highly cited and influential researchers in the world. Dr O'Brien's research is credited for many contributions to the treatment of acute lymphocytic leukemia and chronic lymphocytic leukemia. Year after year, she is ranked nationally at the top in her field by America's Top Doctors, Super Doctors, and America's Top Doctors for Cancer.

Dr O'Brien has authored more than 900 peer-reviewed manuscripts and has given more than 500 lectures at national and international conferences and academic institutions. She is currently the hematology executive officer for SWOG (formerly known as the Southwest Oncology Group Executive Committee) and a board member of the CLL Society. In 2020, she received the Giants of Cancer Care Award for Leukemia.