[Current Status of Stereotactic Ablative Radiotherapy (SABR) for Early-stage 
Non-small Cell Lung Cancer]

High level evidence from randomized studies comparing stereotactic ablative radiotherapy (SABR) to surgery is lacking. Although the results of pooled analysis of two randomized trials for STARS and ROSEL showed that SABR is better tolerated and might lead to better overall survival than surgery for operable clinical stage I non-small cell lung cancer (NSCLC), SABR, however, is only recommended as a preferred treatment option for early stage NSCLC patients who cannot or will not undergo surgery. We, therefore, are waiting for the results of the ongoing randomized studies [Veterans affairs lung cancer surgery or stereotactic radiotherapy in the US (VALOR) and the SABRTooth study in the United Kingdom (SABRTooths)]. Many retrospective and case control studies showed that SABR is safe and effective (local control rate higher than 90%, 5 years survival rate reached 70%), but there are considerable variations in the definitions and staging of lung cancer, operability determination, and surgical approaches to operable lung cancer (open vs video-assisted). Therefore, it is difficult to compare the superiority of radiotherapy and surgery in the treatment of early staged lung cancer. Most studies demonstrated that the efficacy of the two modalities for early staged lung cancer is equivalent; however, due to the limited data, the conclusions from those studies are difficult to be evidence based. Therefore, the controversies will be focusing on the safety and invasiveness of the two treatment modalities. This article will review the ongoing debate in light of these goals.