Benjamin E Onderdonk, MD

Benjamin Ernst Onderdonk, MD, MS, is a radiation oncologist with Rochester Regional Health who treats patients with both cancerous and benign conditions using advanced radiotherapy techniques. He specializes in IMRT/IGRT, brachytherapy, radiosurgery, stereotactic body radiotherapy (SBRT), and radiopharmaceutical therapies, with a particular interest in personalized, patient-centered cancer care. 

He works closely with a multidisciplinary team of specialists across our network to ensure patients receive the right care, from the right provider, at the right location. This coordinated approach provides access to advanced treatment options, specialized expertise, and a seamless experience throughout every stage of care.

Born and raised in Rochester, Dr. Onderdonk’s commitment to oncology is deeply personal. After losing his mother to breast cancer as a child, he developed a strong desire to care for patients and families facing complex diagnoses. He strives to provide thoughtful guidance, steady reassurance, and compassionate care throughout each patient’s treatment journey.

Dr. Onderdonk earned his medical degree from SUNY Upstate Medical University, completed his internship at Memorial Sloan Kettering Cancer Center, and completed residency training in radiation oncology at the University of Chicago, where he also earned a Master of Science in Public Health Sciences. He has contributed to clinical research, national presentations, peer-reviewed publications, and clinical trials.

Outside of medicine, Dr. Onderdonk enjoys spending time with his wife and three children, as well as sailing, hunting, coaching, gardening, beekeeping, fishing, and homesteading activities.