ESTRO 2023 - Abstract Book

S2089

Digital Posters

ESTRO 2023

used for significance (p<0.1) between means (N>30 for all groups). All fractionation is conventional (15-40 depending on RX). Results 903 (6.4%) of all planned fractions were not delivered. 290 (66.7%) of patients had at least 1 day of NC. Of the NC days, 531 (58.8%) can be contributed to facility downtime and 225 (51.7%) of patients experienced at least 1-day of non- compliance from downtime. Breast cancer patients (73.0%) were the only site group to show a significant (p=0.089) increase in NC than patients of other sites (64.8%). Breast cancer patients also had a significantly (p<0.0001) higher rate of missed fractions (10.6%) than all other groups (5.6%). Excluding the breast cancer cohort, all other sites had statistically similar missed fraction rates except for H&N patients (p=0.0349) being lower (4.8%) than the other non-breast sites (5.9%). Patients in the 76-98 age group (76.2%) were the only group to show a significant (p=0.075) increase in NC compared to all other age groups. However, on a per fraction basis, patients in the 46-55 group (13.2%) had significantly higher rates of non-compliance than all other groups (8.15%). The large difference in fractions missed for this age group does not include an outlier, rather a large group of patients (24|53.3%) missing between 3-7 fractions. Excluding the 46-55 group, the 28-35 group (9.7%) had higher (p=0.004) and the 66-75 (7.0%) had fewer percentage of fractions missed than the other age groups which were indistinguishable from each other (7.6%).

Conclusion In a single-room proton center, downtime was seen to cause the majority of missed treatments for patients and helped contribute to 2/3 of patients missing at least 1 treatment. Accounting for facility downtime, breast patients were seen to miss a greater percentage of planned fractions than any other treatment sites. It is postulated that this may be due the more patients skipping some treatment days due to skin reactions common in proton treatments. The eldest group of patients were seen to be the most likely to be non-compliant. This could be due to transportation and other health difficulties. Further analysis is warranted to see other factors, particularly travel distance and socioeconomic factors impacts NC rates at a single-room proton center.

Poster (Digital): RTT treatment planning, OAR and target definitions

PO-2321 Innovative RTT-Led voluming of CSI CTVs and OARs in proton beam therapy (PBT)

C. Thould 1 , J. Davda 1 , J. Gains 1 , P.S. Lim 1 , H. Hyare 2 , Y. Chang 1

1 University College London Hospitals NHS Foundation Trust, Radiotherapy, London, United Kingdom; 2 University College London Hospitals NHS Foundation Trust, Radiology, London, United Kingdom Purpose or Objective To develop a scope of practice and competency framework for RTTs to volume specified neural foramen, CTVs and OARs, combining them with the whole brain and spinal canal in preparation for OTV generation of PBT CSI treatment. To advance RTT skillset and streamline voluming time. Materials and Methods SIOPE guidelines for CSI voluming were used as the basis for developing the atlas and competency documentation for RTTs to use. Targets for RTTs to volume were identified, Table 1. 8 anonymised training cases were selected, 3 with extended head positions and 5 with neutral. Agreed volumes were outlined by two RTTs independently and reviewed in MDT for feedback and approval. RTT competency documentation was devised in conjunction with feedback from MDT sessions. Data were evaluated in the form of feedback discussion from the MDT review with real-time editing of the contours and guidance