Dr. Butler graduated from Georgetown University School of Medicine in Washington, D.C. in 1982.  He started his residency at Wilford Hall USAF Medical Center in San Antonio, Texas in 1982 and then completed his residency as Chief Resident at Stanford University Medical Center in 1986.  After completing his postdoctoral training in 1987, Dr. Butler returned to the Wilford Hall USAF Medical Center where he became both the Chief of Radiation Oncology and the Chief of Brachytherapy. He also joined the faculty at The University of Texas Health Science Center at San Antonio as a Clinical Assistant Professor that same year. Dr. Butler would later join the Baylor College of Medicine where he would eventually become a full professor and the Chief of Radiation Oncology for both the medical school and the VA Hospital. He became the Medical Director of Radiation Oncology at Methodist in 1991, and received his faculty appointment at the Weill Medical School in 2006.  He became Chair of Radiation Oncology at Houston Methodist in 2008.  In 2016, Dr. Butler was named the Jim and Joan Harrell Chair in Radiation Oncology.

Dr. Butler’s research centers on preclinical and clinical studies that combine radiation therapy and gene therapy for the treatment of prostate cancer. In recent years, he has extended these successful studies to other cancers, notably pancreatic cancer. His research interests also include three-dimensional reconstruction of body organs to assist in better localization of radiation therapy.