The role of stereotactic ablative radiotherapy (SBRT) in the management of oligometastatic non small cell lung cancer.

Our understanding of metastatic disease has evolved significantly in the last 20 years. Considered strictly a systemic issue, local treatment would only have significant impact in terms of palliation. However, Hellman and Weichselbaum stated that there might be an intermediate state, in which controlling limited metastatic sites could improve oncologic outcomes. This is called an oligometastatic state, a point between locally confined cancer and widespread disease [1,2]. As treatment with chemotherapy alone for non small cell lung cancer (NSCLC) yields median survivals of 8-11 months [3] and minimal chances of long term survival, new strategies are needed to offer better odds for metastatic patients. Outcomes tend to be better in patients with low volume metastatic disease. [4,5], leading us to question whether the oligometastatic group of patients will gain from a more radical treatment paradigm. In this setting, ablative treatments like surgery or SBRT may provide longer survival and better local control times. There is a rationale for the use of ablative local treatments, as most failures after chemotherapy occur at sites initially affected by disease, and these sites could be a source of further dissemination. Also, chemotherapy resistance can adversely impact resolution of metastatic disease [6]. In rare cases, the abscopal effect (an immune effect arising after radiotherapy in non irradiated metastatic sites) has been described [7,8]. In this review article, we address the impact of SBRT in oligometastatic NSCLC, the most relevant prognostic factors, indications and a site specific review. This review will focus on SBRT for extracranial disease as the role for intracranial SBRT is established. Crown