Review ArticlesDefinition, Biology, and History of Oligometastatic and Oligoprogressive DiseaseFoster, Corey C. MD, MS; Pitroda, Sean P. MD; Weichselbaum, Ralph R. MDAuthor Information From the Department of Radiation and Cellular Oncology, The University of Chicago Medicine, Chicago, IL. Reprints: Ralph R. Weichselbaum, MD, Department of Radiation and Cellular Oncology and the Ludwig Center for Metastasis Research, The University of Chicago Medicine, 5758 S Maryland Ave, MC 9006, Chicago, IL 60637. E-mail: email@example.com. Conflicts of Interest and Source of Funding: R.R.W. has stock and other ownership interests with Boost Therapeutics Inc., Coordination Pharmaceuticals Inc., ImmunoVir LLC, Magi Therapeutics, Oncosenescence, and Reflexion Pharmaceuticals. He has served in a consulting or advisory role for Aettis Inc., AstraZeneca, Coordination Pharmaceuticals Inc., Genus, ImmunoVir LLC, Merck Serono S.A., Nano Proteagen, NKMax America Inc., Reflexion Pharmaceuticals, and Shuttle Pharmaceuticals. He has a patent pending entitled, "Methods and kits for diagnosis and triage of patients with colorectal liver metastases." He has received compensation including travel, accommodations, or expense reimbursement from AstraZeneca and Merck Serono S.A. S.P.P. has a pending patent entitled “Methods and kits for diagnosis and triage of patients with colorectal liver metastases.” For CCF, none were declared. This work was supported by the Virginia and D. K. Ludwig Fund for Cancer Research and the Foglia Foundation. These sources had no role in the conception of this work, the writing of the manuscript, or the decision to submit for publication. The Cancer Journal: 3/4 2020 - Volume 26 - Issue 2 - p 96-99 doi: 10.1097/PPO.0000000000000434 Buy Metrics Abstract Historical theories of metastasis have been informed by the seed and soil hypothesis, the Halsteadian paradigm proposing an orderly spread from local to distant sites, and the presumption that cancer is an inherently systemic process even in the earliest cases. The more contemporary spectrum theory now suggests that the propensity for distant spread exists along a continuum of metastatic virulence. Tumors with limited metastatic potential represent one subset along this spectrum that could potentially be cured with local ablative therapy. Integrating clinical and molecular features to biologically inform the classification of not only oligometastatic or oligoprogressive disease but also the entire metastatic spectrum holds great promise to improve prognostication and inform clinical decision making. To this end, the inclusion of molecular correlative studies and biospecimen collection on prospective protocols is imperative. Copyright © 2020 Wolters Kluwer Health, Inc. All rights reserved.