Oligometastasis refers to a state of limited metastatic disease burden, in which surgical or ablative treatment to all known visible metastases holds promise to extend survival or even effect cure. Stereotactic body radiotherapy is a form of radiation treatment capable of delivering a high biologically effective dose of radiation in a highly conformal manner, with a favorable toxicity profile. Enthusiasm for oligometastasis ablation, however, should be counterbalanced against the limited supporting evidence. It remains unknown to what extent (if any) ablation influences survival or quality of life. Rising clinical equipoise necessitates the completion of randomized controlled trials to assess this, several of which are underway. However, a lack of clear identification criteria or biomarkers to define the oligometastatic state hampers optimal patient selection.
This narrative review explores the evolutionary origins of oligometastasis, the steps of the metastatic process at which oligometastases may arise, and the biomolecular mediators of this state. It discusses clinical outcomes with treatment of oligometastases, ongoing trials, and areas of basic and translational research that may lead to novel biomarkers. These efforts should provide a clearer, biomolecular definition of oligometastatic disease and aid in the accurate selection of patients for ablative therapies.
From the *Department of Radiation Oncology, London Regional Cancer Program, University of Western Ontario, London, Ontario, Canada; †Department of Radiation Oncology, Duke University, Durham, NC; and ‡Department of Radiation Oncology, University of Rochester Medical Center, Rochester, NY.
Conflicts of Interest and Source of Funding: D.A.P. is supported by a Clinician-Scientist Grant from the Ontario Institute for Cancer Research. The other authors have disclosed that they have no significant relationships with, or financial interest in, any commercial companies pertaining to this article.
Reprints: David A. Palma, London Health Sciences Centre, 790 Commissioners Rd East, London, Ontario, Canada N6A 4L6. E-mail: email@example.com.
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