Code of Practice and Recommendations for Stereotactic Body Radiotherapy

In November 2016, the NCS installed a new subcommittee to write a code of practice for stereotactic body radiotherapy (SBRT). The aim of this code of practice is to describe the basic requirements and provide guidelines for safe and high-quality SBRT. The guidelines are based on current literature as well as clinical experience from the participating members of the NCS subcommittee.

The introduction describes the characteristics that define SBRT, relates this code of practice to other publications on this topic and gives a short overview of the current report. Chapter 2 covers general aspects of motion management, where the main message is that inter-and intra-fraction motion should be minimized by using a reproducible, stable and comfortable patient set-up. In addition, this chapter contains recommendations to reduce the target volume in case of moving targets by using for example a Mid-Ventilation approach, gating, tracking, breath hold or abdominal compression. Subsequently, chapter 3 discusses pre-treatment imaging and connects to chapter 2 by stating that it is required to use 4D-computed tomography (CT) imaging for moving tumors. In addition, this chapter gives recommendations about the slice thickness (1-3 mm), the number of phases to be used in 4D-CT imaging (a minimum of 8) and a few other considerations with regard to using magnetic resonance imaging and positron emission tomography in combination with CT imaging for delineation and treatment planning. In chapter 4 the report progresses to the next step in the radiotherapy chain by discussing the aspects of treatment planning that are of special importance for SBRT. The main points of attention in this respect are using correct procedures and detectors for small field dosimetry, accurate modelling of leaf tips and leaf gaps and using advanced dose calculation algorithms (i.e. at least type B).  Chapter 5 then starts with sections on target visualization during treatment and the use of position verification protocols. It continues with elaborating on the uncertainties in the radiotherapy chain and how to reflect these correctly in planning target volume margins for hypofractionated treatments.  The main requirements stated in this chapter are the use of online image guidance and the need for investigating and quantification of all uncertainties in the treatment chain. SBRT-specific quality assurance (QA) is addressed in chapter 6, including QA of the treatment machine, the patient plan and of the overall process. With regard to machine QA, tighter requirements are given for the isocenter and couch movement accuracy, while additional requirements are listed for special devices or techniques like robotic couches, gating and tracking. Additionally, the chapter gives recommendations for QA of individual treatment plans for SBRT. Next, aspects of process management and control are discussed, and the chapter ends with some considerations regarding end-to-end testing for SBRT. The report concludes with the chapter on technological developments, where emerging techniques that are not yet standard practice for SBRT, like proton therapy, new breathing motion management systems and online adaptive (MRI or cone-beam CT based) radiotherapy, are briefly discussed.

As SBRT is a technique that requires high accuracy in the entire treatment chain and because of its application to a wide range of tumor sites, this report had to cover a lot of topics. Nevertheless, the subcommittee has attempted to make a complete and thorough report, that should be considered as a set of guidelines for proper and safe application of SBRT.

https://doi.org/10.25030/ncs-037