Dr. Shannon Macdonald is the Medical Director at Southwest Florida Protons. Prior to 2025, she served as an Associate Professor of Radiation Oncology at Harvard Medical School. At Massachusetts General Hospital, she held several leadership roles in the Department of Radiation Oncology, including Director of the Base of Skull and Sarcoma Services and member of the Pediatric Service. Earlier in her career, she was a member of the Breast Service from 2006 to 2018 and served as its director.

Dr. Macdonald’s clinical expertise focuses on the treatment of breast, pediatric, and base-of-skull tumors, as well as sarcomas, using proton therapy. She has worked across Dana-Farber Cancer Institute, Brigham and Women’s Hospital, and Boston Children’s Hospital, providing proton therapy for pediatric patients and consulting on proton therapy for select adult patients, while actively promoting collaboration and the appropriate utilization of proton therapy.

Providing comprehensive, patient- and family-centered care is the most fulfilling aspect of Dr. Macdonald’s career. She values shared leadership and enjoys leading teams and projects that emphasize communication, collegiality, and professional well-being.

Dr. Macdonald currently serves as Chair of Radiation Oncology for the Children’s Oncology Group (COG) and as a primary investigator or clinical chair for two large, multi-institutional clinical trials. She is the Principal Investigator of COG ACNS2021, a Central Nervous System germ cell tumor trial that opened in 2021 across COG sites in the United States, Canada, Australia, and New Zealand. She also serves as the Clinical Chair of the Radiotherapy Comparative Effectiveness (RADCOMP) Consortium Trial.