Stereotactic ablative body radiation for oligometastatic and oligoprogressive disease

One area in which stereotactic ablative body radiation (SABR) has developed as a viable treatment modality over the past decade has been in metastatic disease. Several related categories of this malignancy have been defined. Oligometastasis is the setting of limited metastases, with the definition of “limited” varying by study. The most common classification is 3 or less metastatic lesions (1,2), though studies with one to eight sites of disease exist. Oligoprogression refers to malignancy that has progressed in a limited number of sites, while oligo-recurrence occurs after definitive treatment for locoregional disease, followed by the manifestation of metastases in a limited fashion. Retrospective and prospective trials have focused on all three of these scenarios. The aim of the current manuscript is to review the underlying biologic rationale and clinical data for SABR in the setting of oligometastases and oligoprogression to provide a sense of the current state of ablative radiation in these settings, with regard to which patients may be candidates for this approach, what high impact trials are currently addressing this issue, and where future directions may lie