Dr. MacDonald is a radiation oncologist at Mass General Brigham specializing in proton beam radiation. She specializes in pediatric and skull base sarcoma. She is the director of the sarcoma and skull base services at the Massachusetts General Hospital. She has run several prospective trials and is the clinical co-chair of the recently completed RADCOMP trial, a PCORI-sponsored multi-institutional trial comparing Protons and Photons for Locally Advanced Breast Cancer. She is the study chair for ACNS2021, a prospective clinical trial for CNS Non-germinomatous germ cell tumors. Dr. MacDonald is recognized nationally and internationally as an expert in proton therapy. She also writes narratively on topics including the use of telemedicine across state lines to provide equitable care for rare diseases.