A systematic Review: Comparing the Effectiveness of Internal and External Markers as Surrogates for Tracking Tumour Motion in Patients Undergoing Stereotactic Ablative Body Radiotherapy for Non Small Cell Lung Cancer

Aim: The aim of this study is to evaluate if internal or external markers are effective at tracking the tumour when treating NSCLC patients with SABR. Background: Stereotactic ablative radiotherapy (SABR) has improved the survival for medically inoperable patients with non-small cell lung cancer (NSCLC). Respiratory tumour motion is challenging when implementing SABR treatment. This tumour motion can be localised and tracked by either internal or external markers. Method: A systematic review was conducted following PRISMA guidelines, to assess the treatment of NSCLC with SABR utilising either internal or external surrogates to determine which is more efficient at tracking tumour motion. The secondary endpoint was analysing if either surrogate demonstrated less toxicities and an improved rate of local control and overall survival outcomes. Eligible studies of SABR using surrogates to localise the tumour were retrieved through extensive searches of the Medline, CINAHL Plus, PubMed, Cochrane Library and Science Direct databases from 2008 to May 2016. Result: The search returned 120 articles; 17 met the inclusion criteria. No one paper had the ability to answer both primary and secondary outcomes. Four articles were included for analysis of the primary outcomes and 13 articles for secondary outcomes. From these articles data was extracted and analysed. Conclusion: The primary conclusion from the systematic review suggests internal markers are more effective at tumour tracking. The correlation between tumour and external marker did not demonstrate accurate results. Furthermore, due to technological advances, radiotherapy systems are incorporating both surrogates to track the tumour, hence the reason only a select few papers are included in the primary outcomes. Toxicity outcomes show that external markers are more beneficial as they incur less side effects. In contrast, local control and overall survival have better outcomes when using internal markers.msc_radunpub2503_ethesesunpu