Susan O'Brien MD is a Professor in the Division of Hematology/Oncology at the University of California, Irvine. She has authored over 900 peer-reviewed manuscripts and has given over 500 lectures in national and international conferences and academic institutions.

Dr. O’Brien is considered a leading Leukemia expert world-wide with an H index of 170. She is listed in the 1% of the most highly cited and influential researchers in the world. Her research is credited for many and sustained contributions to the treatment of Acute Lymphocytic Leukemia (ALL) as well as Chronic Lymphocytic Leukemia (CLL). She is the SWOG Hematology Executive and a Board member of the CLL Society.

In 2020 Dr. O’Brien received the Giants of Cancer Care Award for Leukemia.