Patterns of practice for adaptive and real-time radiation therapy: part I intra-fraction motion

Abstract

Purpose or Objective The patterns of practice for adaptive and real-time radiation therapy (POP-ART RT) study aims to determine to which extent and how these methods are used in clinical practice and to understand the barriers to implementation. Here we report on part I: real-time respiratory motion management (RRMM). Material and Methods An institution-specific questionnaire developed during the 2nd ESTRO physics workshop was distributed worldwide. The focus was both on current practice and wishes for implementation. Therefore, centres not (yet) doing RRMM were encouraged to participate. RRMM was defined as the use of gating in free-breathing (FB) or breath-hold (BH), or tracking if the beam is continuously realigned with the target in real-time (via robotic or gimbal guidance, MLC or couch tracking). Respondents were asked if they used RRMM for selected tumor sites, the percentage of patients treated with RRMM, eligibility criteria and the monitoring signal used to guide gating or tracking. Respondents were also asked if they wished 1) to change or expand their use of RRMM for a tumor site already treated with RRMM and 2) to implement RRMM for a new tumor site and to rank the barriers to implementation in order of importance. Results The questionnaire was filled out by 200 centres from 41 countries. 68% of respondents used RRMM in at least one tumor site (“users”). Inspiration BH was the dominant technique for breast and lymphoma, whereas the spread in technique was greater for other sites (Table 1). Within any given tumor site, users only applied RRMM in a subset of patients. The most frequently selected percentage range of patients treated using RRMM was <25% for lung, pancreas and lymphoma, 25-50% for breast and >75% for liver. However, for liver and pancreas, >50% of users applied RRMM in >50% of patients. The main selection criteria was “left breast” (76%) for breast and SBRT (~50%) for lung, liver and pancreas. Across all tumor sites, external marker was the main RRMM signal used by >60% of respondents. For breast and lymphoma this was followed by surface imaging and breathing volume. KV/MV imaging was frequently used for liver and pancreas (with markers) and for lung (with or without markers) (Fig 1a). Tracking was mainly done on robotic linacs with hybrid monitoring. For breast and lung, 36% and 49% of the centres respectively wish to expand or implement RRMM (Fig 1b). In contrast, for liver and pancreas >55% of centres do not use RRMM and do not wish to implement it. Overall 71% of centres wish to implement RRMM for any new treatment site (Fig 1c) but human/financial resources and capacity on machine were the main barriers Conclusion Thirty-two percent of respondents do not use any form of RRMM. Although RRMM was common in the thorax, it was generally applied for less than half of the patients. There is an unmet need for RRMM solutions, particularly in lung cancer. The main barriers to implement RRMM are human/financial resources and capacity on the machine.