Required transition from research to clinical application: Report on the 4D treatment planning workshops 2014 and 2015

Abstract

Since 2009, a 4D treatment planning workshop has taken place annually, gathering researchers working on the treatment of moving targets, mainly with scanned ion beams. Topics discussed during the workshops range from problems of time resolved imaging, the challenges of motion modelling, the implementation of 4D capabilities for treatment planning, up to different aspects related to 4D dosimetry and treatment verification. This report gives an overview on topics discussed at the 4D workshops in 2014 and 2015. It summarizes recent findings, developments and challenges in the field and discusses the relevant literature of the recent years. The report is structured in three parts pointing out developments in the context of understanding moving geometries, of treating moving targets and of 4D quality assurance (QA) and 4D dosimetry. The community represented at the 4D workshops agrees that research in the context of treating moving targets with scanned ion beams faces a crucial phase of clinical translation. In the coming years it will be important to define standards for motion monitoring, to establish 4D treatment planning guidelines and to develop 4D QA tools. These basic requirements for the clinical application of scanned ion beams to moving targets could e.g. be determined by a dedicated ESTRO task group. Besides reviewing recent research results and pointing out urgent needs when treating moving targets with scanned ion beams, the report also gives an outlook on the upcoming 4D workshop organized at the University Medical Center Groningen (UMCG) in the Netherlands at the end of 2016.

Dose assessment for patients with stage I non-small cell lung cancer receiving passive scattering carbon-ion radiotherapy using daily computed tomographic images: A prospective study

“…Second, we did not consider the intrafractional changes, such as tumor respiratory motion during treatment, which also affected the dose distribution [25]. A 4D treatment plan based on daily 4DCT or real-time tumor tracking is a promising method to reduce these uncertainties, which have been recently discussed in particle RT [26][27][28]; moreover, the DIR method has its own uncertainties, although the dose warping errors are generally less than 3% [29,30]. Furthermore, a larger margin may be required to compensate for the interfractional deviations in BM while employing a scanning pencil beam technology; consequently, the effects induced by the changes in the WEL may be greater than those observed in the present study.…”

4D robust optimization including uncertainties in time structures can reduce the interplay effect in proton pencil beam scanning radiation therapy

“…1. a standard 4D robustly optimized plan, 2. a rescanned version of plan (1), 3. a 4D robustly optimized plan with time structures according to method 1, described in Section 2.A.2, with 9 scenarios, 4. a rescanned version of plan (3), 5. two 4D robustly optimized plans with time structures according to method 2, described in Section 2.A.2, with 10 and 40 scenarios, respectively, and 6. rescanned versions of the plans in (5).…”

Log file‐based dose reconstruction and accumulation for 4D adaptive pencil beam scanned proton therapy in a clinical treatment planning system: Implementation and proof‐of‐concept

“…Nevertheless, by taking such an approach, the treatment plan may be optimized to be robust against scenarios that might never occur during the actual treatment. Therefore, the actual dose degradation per fraction, which remains unknown in the multiscenario approach, is also of great importance in the clinical assessment of the treatment quality and has been identified by the community as an “essential [need] for a comprehensive and safe clinical implementation of scanned particle treatment for moving targets.” Subsequently accumulated dose distributions during the course of treatment can be used to support decisions on the treatment adequacy and the need of treatment adaptation. Furthermore, a realistic accumulated dose distribution for the full treatment course is a better basis for correlations with side effects and recurrences.…”