Robert D. Timmerman, MD, is Professor of Radiation Oncology and Neurosurgery, Chair of Radiation  Oncology, and Effie Marie Cain Distinguished Chair in Cancer Therapy Research at the University of Texas Southwestern Medical Center in Dallas, Texas.  Dr. Timmerman graduated from Iowa State University with a Bachelor of Science degree in Nuclear Engineering and from the University of Tennessee with a Master of Science degree in Reactor Physics.  After finishing medical school in his home state of South Dakota, he completed a residency in Radiation Oncology at The Johns Hopkins Hospital.  Functioning primarily as a clinician specializing in highly potent and focused stereotactic radiotherapy, he has treated thousands of adult and pediatric patients with brain tumors.  He was involved early in the translation of this approach to treat tumors in the body.  He was the principal investigator or co-investigator on several prospective trials designed to evaluate the efficacy and toxicity of stereotactic ablative radiotherapy (SAbR) in lung, liver, spine, breast, and prostate sites.  He is the national principal investigator of several Radiation Therapy Oncology Group trials using this therapy in patients with early stage lung cancer.