New concepts and insights into the role of radiation therapy in extracranial metastatic disease

Stereotactic ablative radiotherapy (SABR) is a form of very precise radiotherapy that delivers high doses to tumors while sparing adjacent organs at risk. Recent data show that SABR is a low-toxic and highly effective local treatment for metastatic localizations in various organs, obtaining local control rates of approximately 80%. Experimental evidence also suggests that SABR may play an important therapeutic role in oligometastatic/oligorecurrent/ oligoprogressive patients, a subset of cancer patients who are probably in an intermediate disease state between localized disease and widespread dissemination. There is a strong biological and clinical rationale in combining the high local control rates achievable with SABR with effective systemic therapies, and recent results of pilot studies indicate that SABR may have a potential impact on prognosis in this subgroup of patients, being 'curative' in around 20-25% of cases. This paper reviews and discusses basic concepts and clinical applications of SABR in oligometastatic patients.