Impact of neuroradiologists’ input on peer review meetings for CNS radiotherapy treatment planning.

2043 Background: Evidence shows radiologists’ involvement improves planning accuracy, especially in complex anatomical areas. However, their participation remains limited. This prospective observational study evaluates the impact of neuroradiologists' input on changes to radiotherapy (RT) plans during peer review meetings. Methods: Data were collected from 205 patients with CNS tumours planned for radiotherapy between May 2022 and October 2023. We recorded demographics, diagnostic and RT planning scans, and therapy received. All images were reviewed by a neuroradiologist, with RT changes classified as major (affecting cure or disease control) or minor (affecting target volumes or organs at risk). Summary statistics were calculated, and Pearson chi-squared tests assessed whether changes in RT plans varied by tumour type, time since diagnosis, and neuroradiologist findings. Data were analyzed using STATA SE v.17. Results: Of 205 patients, 81 (40%) had gliomas, 77 (38%) had brain metastases, 23 (11%) had meningiomas, 17 (8%) had schwannomas, and 7 (3%) had pituitary tumours. The mean age was 60 years (SD 14), 56% were male, and 36% were treatment-naïve. All but one had MRI scans, 128 (62%) had CT scans, and 9 (4.4%) had PET scans. The median number of diagnostic scans per patient was 2 (IQR 2-3), and all had two planning scans. The median interval between diagnosis and RT planning scans was 35 days (IQR 21-61). Disease progression was observed in 67 (33%) patients. Major and minor changes to RT plans were reported in 35 (17%) and 78 (38%) patients, respectively. A higher proportion of RT plans changed for brain metastasis (26% & 40%) and glioma (11% & 43%). Changes were not associated with tumour type (p = 0.07) or time since diagnosis (p = 0.12), but were significantly associated with neuroradiologist findings (p < 0.0001). Conclusions: Neuroradiologists' assessments led to major and minor changes in RT plans, regardless of tumour classification or interval since diagnosis. This expertise can enhance RT plan accuracy, improving patient outcomes. Changes to radiotherapy treatments as per RCR categories and by tumour type, time interval, and neuroradiologist findings. Changes to radiotherapy plan Major change(N= 35) Minor change(N= 78) No change(N=92) P value* Total 17 % 38% 45% Tumour classification 0.07 Glioma 9 (11.1) 35 (43.2) 37 (45.7) Meningioma 3 (13.0) 7 (30.4) 13 (56.5) Schwannoma 2 (11.8) 3 (17.7) 4 (57.1) Pituitary tumour 1 (14.3) 2 (28.6) 4 (70.6) Metastasis 20 (26.0) 31 (40.3) 26 (33.8) Time interval, weeks 0.12 Less than 8 27 (77.2) 61 (78.2) 59 (64.1) 8- 4 (11.4) 10 (12.8) 20 (21.7) 16- 1 (2.9) 3 (3.9) 7 (7.6) 24- - 2 (2.6) 1 (1.1) 30- - 2 (2.6) 3 (3.3) 38- 3 (8.6) - 2 (2.2) Neuroradiologist findings <0.0001