Patients with oligometastates may exist in an intermediate state between local and truly systemic disease. For such patients, surgery with or without systemic treatment can be curative or achieve extended progression free survival beyond that traditionally expected. However, only a minority of patients can physiologically tolerate surgery or have all their disease sites resected. Recent technologic advances have enabled stereotactic ablative radiotherapy (SABR), which is characterised by ultra high doses delivered with accurate image guidance. With local control rates comparable to surgery, SABR represents an opportunity to improve clinical outcomes for a wide range of patients that has not existed in the past. 

Randomized controlled trials of oligometastatic intra-cranial disease have confirmed survival improvements. Extra-cranially, prospective phase II evidence suggests SABR can be delivered to any site in the body safely with local control rates exceeding 90%. Although there is no randomized evidence to confirm oligometastatic patients receiving SABR have improved survival, there is evidence that this might be the case for appropriately selected patients. Assessment of metastatic tissue samples for microRNA expression correctly predicts whether oligometastatic patients become polymetastatic or remain oligometastatic. Similarly, mathematical modelling of metastatic progression show that while some metastatic sites remain local, others evolve the ability to secondarily metastasize to new sites. This suggests even if all oligometastatic sites are not treated the natural history of metastatic progression may be altered. Similar observations have been made in patients receiving systemic chemotherapy, where after initial control, progression is oligoprogressive and limited to selected sites. Here, SABR to oligoprogressive sites, would enable continuation of the current line of systemic therapy.
By the end of the year randomized controlled trial assessing the efficacy of SABR for oligometastatic patients will have been activated. These will answer whether the combination of SABR and systemic therapy will become the new standard for patients with limited metastasis.