S2359
Physics - Quality assurance and auditing
ESTRO 2026
1.29 [1.16–1.43] (p > 0.05) and PCI increasing from 0.72 [0.54–0.85] to 0.76 [0.69–0.84] (p > 0.05). MGI decreased from 5.34 [4.03–8.62] to 4.95 [4.00–6.44] (p > 0.05). For benign cases, coverage showed a statistically significant decrease from 1.00 [1.00–1.00] to 0.99 [0.96–1.00] (p < 0.01). Conformity showed a statistically significant improvement, with PDS reducing from 1.64 [1.40–2.05] to 1.26 [1.15–1.36] (p < 0.01). The PCI increased from 0.61 [0.51–0.72] to 0.78 [0.71–0.86] (p > 0.05), and the MGI decreased from 5.88 [5.28–7.27] to 5.43 [4.34–7.59] (p > 0.05).Across all planning cases, there was a significant reduction in PDS variability in 2025 (p < 0.01). For multi-met cases only, a significant reduction in PCI variance was observed (p = 0.02).
10.1136/bmjopen-2024-097810. Keywords: APPROACH, benchmark, OAR
Digital Poster Highlight 2186
Past and Present Trends in SRS Benchmark Planning from a National RT QA Programme Luke Gilling 1,2 , Patricia Diez 1,2 , Sarah Osman 1,3 , Elizabeth Miles 1,2 , Rushil Patel 1,2 1 National RTQA, Radiotherapy Trials Quality Assurance Group, London, United Kingdom. 2 Department of Radiotherapy Physics, Mount Vernon Cancer Centre, London, United Kingdom. 3 Department of Radiotherapy Physics, University College London Hospitals, London, United Kingdom Purpose/Objective: This study evaluates the progression of Stereotactic Radiosurgery (SRS) planning within a national framework. It compares planning submissions from a national SRS QA programme conducted in both 2016 and 2025. Material/Methods: In 2016 and 2025, participating centres submitted benchmark planning cases: two multi-metastatic (multi-met) and two benign disease cases. Submissions included DICOM data and a plan assessment form with dose and volume metrics. Target coverage, prescription dose spillage (PDS), modified gradient index (MGI), and Paddick conformity index (PCI) were independently calculated using the dose and volume metrics.
Conclusion: The 2025 SRS QA programme demonstrated that reduced target coverage was accompanied by improved dose conformity, with the change reaching statistical significance for benign cases. Crucially, a significant reduction in the variance of conformity metrics (PDS and PCI) was observed, suggesting an improvement in national standardisation. These findings suggest an emerging clinical trend toward prioritising high target conformity and steeper dose gradients. The observed increase in conformity may in part reflect a shift in practice aimed at reducing the risk of radionecrosis [1-3]. References: 1. Milano MT, Grimm J, Niemierko A, Soltys SG, Moiseenko V, Redmond KJ, et al. Single- and multifraction stereotactic radiosurgery dose/volume tolerances of the brain. Int J Radiat Oncol Biol Phys. 2021;110(1):68–86.2.Patel KR, Burri SH, Asher AL, Crocker IR, Fraser RW, Zhang C, et al. Comparing preoperative with postoperative stereotactic radiosurgery for resectable brain metastases: a multi- institutional analysis. Neurosurgery. 2016;79(2):279– 85.3.Sharma M, Jia X, Ahluwalia M, Barnett GH, Vogelbaum MA, Chao ST, et al. First follow-up radiographic response is one of the predictors of local tumor progression and radiation necrosis after stereotactic radiosurgery for brain metastases. Cancer Med. 2017;6(9):2076–86. Keywords: SRS, QA, Planning
The Mann-Whitney U test assessed changes in metrics between cohorts, and the Fligner–Killeen test assessed changes in variance. Results: 20 submissions were received in 2016 and 21 in 2025. The SRS delivery platforms included CyberKnife (N2016=4, N2025=2), Gamma Knife (N2016=6, N2025=6), and gantry-mounted linacs (N2016=10, N2025=13). For all planning cases, differences in coverage, conformity, and PCI were observed between 2016 and 2025 (Figures 1 and 2). All results are reported as median [IQR].In multi-met planning, coverage decreased from 1.00 [0.99–1.00] in 2016 to 0.99 [0.98–1.00] in 2025 (p > 0.05). Conformity metrics improved, with PDS reducing from 1.39 [1.17–1.85] to
Made with FlippingBook - Share PDF online