A review of surface guidance in extracranial stereotactic body radiotherapy (SBRT/SABR) for set-up and intra-fraction motion management

INTRODUCTION: Surface guidance (SG) radiotherapy (RT) is now used by many radiotherapy departments globally and has expanded in popularity over the last number of years. A number of commercial systems are available. SG has routinely been used and is well established for cranial stereotactic radiosurgery (SRS) patient set ups and intra-fraction motion monitoring. However, data is limited in relation to its clinical use for extracranial stereotactic body radiotherapy (SBRT), particularly for targets which are impacted by respiratory motion such as the lung and liver. OBJECTIVE & INFORMATION SOURCE: A review of available literature was carried out on 24th October 2021 to assess the clinical feasibility and use of SG in SBRT via PubMed. METHODS: Eligibility Criteria The search criteria involved identifying articles where SG is used in extracranial SBRT. Risk of Bias To eliminate the risk of bias, any particular commercial system was not the focus of the review and not included in the search criteria. Numerous clinical terms for similar things were used to reduce the risk of missing papers e.g. SBRT and SABR. Search Criteria The PRISMA checklist was used. Searching for “surface guidance and radiotherapy” yielded 3271 results, where as “SGRT” alone returned 72 results, when the search term was narrowed down using different iterations of SG and SBRT, only 6 results were available. Of these, 4 had reviewed clinical data in relation to SG and SBRT for patient set up and intra-fraction motion monitoring. RESULTS: The 4 studies indicate positive results for using SG with sufficient image guidance (IG) for both patient set up and intra-fraction monitoring during SBRT. This was observed both in free breathing and in patients with respiratory motion management being employed such as deep inspiration breath-hold (DIBH) techniques. All used multiple IGRT solutions to verify localisation pre-treatment in conjunction with SG. Limitations The number of studies available which report using SG in SBRT is extremely limited. All centres had also installed SG systems therefore this could result in an unconditional bias in using the system positively. CONCLUSION: SG can be used for SBRT set-ups and intra-fraction motion monitoring once sufficient IG is used to verify target localisation for treatment.