Patterns of practice for adaptive and real-time radiation therapy (POP-ART RT) part II: Offline and online plan adaption for interfractional changes

Abstract

Purpose: The POP-ART RT study aims to determine to what extent and how intrafractional real-time respiratory motion management (RRMM), and plan adaptation for interfractional anatomical changes (ART) are used in clinical practice and to understand barriers to implementation. Here we report on part II: ART using more than one plan per target per treatment course.

Materials and methods: A questionnaire on the current practice of ART, wishes for expansion or implementation, and barriers to implementation was distributed worldwide. Four types of ART were discriminated: daily online replanning, online plan library, protocolled offline replanning (all three based on a protocol), and ad-hoc offline replanning.

Results: The questionnaire was completed by 177 centres from 40 countries. ART was used by 61% of respondents (31% with protocol) for a median (range) of 3 (1-8) tumour sites. CBCT/MVCT was the main imaging modality except for online daily replanning (11 users) where 10 users used MR. Two thirds of respondents wished to implement ART for a new tumour site; 40% of these had plans to do it in the next 2 years. Human/material resources and technical limitations were the main barriers to further use and implementation.

Conclusions: ART was used for a broad range of tumour sites, mainly with ad-hoc offline replanning and for a median of 3 tumour sites. There was a large interest in implementing ART for more tumour sites, mainly limited by human/material resources and technical limitations. Daily online replanning was primarily performed on MR-linacs.

Keywords: Adaptive radiotherapy; Image-guided radiotherapy (IGRT); Interfractional motion; MR-guided radiotherapy; Plan library; Plan of the day.

Fig. 1

For the various tumour sites, fractions (bar heights) of users applying the defined four types of ART (bar pattern). Colours show percentage of patients having more than one plan for the offline approaches. For breast and prostate, one institution did not specify the type of ART.

Fig. 2

For the various tumour sites, fractions of users that apply ART to recover target dose and/or to improve OAR sparing. Bar patterns indicate which type of ART is performed for site-specific graphs. Note that due to the mix of technique for different tumour sites, the bars for “any” do not have a pattern indicating technique.

Fig. 3

(a) For the various tumour sites, fractions of users that use given imaging modalities to guide adaption (more than one response possible) (b) fractions of users that apply given QA methods (more than on response possible). Bar patterns point at the four defined types of ART. Not that due to the mix of technique for different tumour sites, the bars for “any” do not have a pattern indicating technique.

Fig. 4

(a) For the various tumour sites, fractions of ART users that wish to change technique or increase the rate of adaption (dark blue) or not (medium blue) as a priority. Respondents not applying ART (non-users) but wishing to implement it to this site in priority (light blue) or not (grey). (b) Overall fractions of respondents (current users and non-users) wishing to implement ART for any new tumour site (blue, green and yellow) or not (red). (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)

Fig. 5

Histogram of ranks given to the barriers to further use for an existing ART tumour site (left) or implementation for a new ART tumour site (right). A lower rank (towards red) indicates high importance while a higher rank (towards blue) indicates lower importance. The grey bars indicate the number of institutions that considered the barrier “not relevant”.