Patterns Of Practice for Adaptive and Real-Time Particle Therapy (POP-ART PT), part II: Plan adaptation for interfractional changes

Real-time respiratory motion management (RRMM, intra-fraction geometrical intervention) and Adaptive Particle Therapy (APT, inter-fraction adaptation of treatment plans) enable to account for anatomical variations and changes to optimize target coverage and organs-at-risk sparing. However, their current clinical implementation is unclear and expected to be highly heterogeneous. An institutional questionnaire, Patterns Of Practice for Adaptive and Real-Time Particle Therapy (POP-ART-PT), was distributed between 2021/01-06 to evaluate current clinical practice and wishes and barriers of the implementation. Here, we summarise the international survey results on APT for mitigation of interfractional anatomical changes from 70 particle therapy centers in 17 countries.

The response rate was 100% for Europe, 96% for Japan and 53% for USA. Of the 68 centers in operation, 84% (Figure1a) were APT users for at least one treatment site, with head and neck being the most common. APT was mostly performed offline (ad-hoc or per protocol) with only two users of online APT (plan library) and none using online daily replanning. Plan adaptation was in all cases motivated by both, target and OAR dose considerations (Figure1b). The most common imaging modality guiding APT was X-ray computed tomography. Sixty-eight percent of users plan to increase or change their APT technique. The greatest barriers to implementation were lack of integrated and efficient workflows and human resources (Figure2)

Offline APT has been widely implemented internationally, but online APT is still very rarely used. More research and development for integrated and efficient workflow is needed to facilitate the use of offline APT and enable online APT.