 ASTRO has a membership of more than 10,000 members covering a range of professions including Radiation Oncologist, Radiation Therapists, Medical Dosimetrists Medical Physicists, Radiation Oncology Nurses and Radiation Biologists.The organization began in 1958 as the American Club of Therapeutic Radiologists.In 1966 it became the American Society for Therapeutic Radiologists (ASTR).