Ralph. R Weichselbaum, MD is the Daniel K. Ludwig Distinguished Professor and Chairman of The Department of Radiation and Cellular Oncology, and co-Director of the Ludwig Center for Metastasis Research at The University of Chicago. Dr. Weichselbaum made discoveries in basic mechanisms of signal transduction and gene expression of cytokine genes and immediate early genes following radiation exposure that led to translational investigations into radioinducible gene therapy and the interaction of radiation and Herpes Simplex Virus. Drs. Weichselbaum and Samuel Hellman proposed the spectrum theory of metastasis, predicting that some patients will develop only limited metastatic disease, termed “oligometastasis.” This concept changed clinical practice, resulting in the administration of curative regional therapy to those patients with oligometastatic disease. Dr. Weichselbaum and colleagues are currently investigating the relationship between radiotherapy and immunotherapy, a logical extension of investigations into the local and systemic effects of radiation. Dr. Weichselbaum is a member of ASTRO, the National Academy of Medicine, and the American Association of Physicians. In 2018 he received the David A. Karnofsky Memorial Award and Lecture at the ASCO Annual Meeting, he also received the ASTRO Gold Medal Award at the 60th Annual Meeting. He has over 900 publications and over 50 patents.