S2014
Physics - Dose prediction/calculation, optimisation and applications for photon and electron planning
ESTRO 2026
significance, scalp dose–response relationships and optimization strategies to mitigate this adverse effect remain poorly characterized in daily practice.This study aimed to (1) identify dosimetric thresholds predictive of alopecia (CTCAE v5.0), (2) evaluate the impact of different scalp dose optimization techniques, and (3) propose practical recommendations for treatment planning. Material/Methods: A retrospective analysis was conducted on 25 patients treated with CSI for central nervous system tumors between 2018 and 2023. Patients were classified according to the presence or absence of grade II alopecia (n=12 vs n=13) and the applied optimization strategy: no optimization, anterior–posterior optimization, or anterior–median–posterior sector optimization.For each plan, scalp dose metrics (D1, D2, D50, Dmedian, D95, D98, D99) were extracted. Statistical analyses included non-parametric tests (Mann–Whitney, Spearman) and ROC curve analysis to identify predictive thresholds of alopecia. Results: Patients with grade II alopecia received significantly higher doses to the scalp : Dmedian = 32.3 Gy vs 26.1 Gy (p=0.003); D1 = 44.8 Gy vs 38.5 Gy (p=0.02). A D1 > 40.1 Gy was associated with a higher risk of grade II alopecia (AUC=0.85). A Dmedian > 30.4 Gy was identified as an independent predictor of alopecia (OR=5.2; 95% CI [1.8–14.6]; p=0.002).For a prescribed CSI dose of 36 Gy/20 fractions followed by a 54 Gy boost, the mean scalp Dmedian was:No optimization:37.6 GyAnterior–posterior optimization: 34.9 Gy ( − 2.7 Gy reduction)Anterior–median–posterior optimization: 31.1 Gy ( − 6.5 Gy reduction, p<0.05).This latter strategy also decreased D99 (17.8 Gy vs 22.0 Gy, p<0.05) and D95 (22.3 Gy vs 26.4 Gy, p<0.05), without compromising PTV coverage. Conclusion: This study demonstrates that tailored scalp optimization significantly reduces the risk of complete alopecia after CSI. A Dmedian threshold of 30.4 Gy represents a robust predictor of alopecia. The anterior–median–posterior optimization strategy offers the most effective scalp sparing, particularly at superficial layers (D99–D95), without affecting target coverage. Systematic integration of scalp constraints in CSI planning should be prioritized, especially for pediatric and young adult patients. Future work will aim to validate these findings in a larger, prospective cohort. References: Quesada S, Guichard A, Fiteni F. Cancer-Related Alopecia: From Etiologies to Global Management. Cancers (Basel). 2021 Nov 5;13(21):5556. doi: 10.3390/cancers13215556. PMID: 34771716; PMCID: PMC8583126.Satragno C, Verrico A, Giannelli F, Ferrero A, Campora S, Turazzi M, Cavagnetto F, Schiavetti I,
Figure 2: Exemple of source configuration (left) and tally configuration (right)in Blender environment Results: The pyPenred implementation was validated against penRed's original benchmarks, confirming perfect agreement between the two. To assess performance, we benchmarked the execution time against the native C++ code. Results show that a locally compiled pyPenred introduces a minimal average overhead of only 1.5%. Pre-compiled, pip-installable packages for Linux, Windows, and macOS exhibit a slightly higher penalty of 3.15%. This small cost is a worthwhile trade- off for the drastic simplification in setup and integration. Conclusion: In summary, the pyPenred module and the Blender plug-in collectively transform penRed into an accessible, integrated and user-friendly simulation platform. By bridging high-performance computing with modern Python workflows, this work lowers the barrier to advanced MC simulations, broadening the impact of the PENELOPE and penRed ecosystem. References: V. Giménez-Alventosa, V. Giménez Gómez, S. Oliver, PenRed: Anextensible and parallel Monte-Carlo framework for radiation transportbased on PENELOPE, Computer Physics Communications 267 (2021)108065. doi:https://doi.org/10.1016/j.cpc.2021.108065. Keywords: Monte Carlo, penRed, Python Scalp Dose Optimization to Prevent Alopecia in Craniospinal Radiotherapy: A Retrospective Dosimetric Analysis Luc OLLIVIER, Dominique Le Denmat, Anne Garnier, Gregory Delpon, Camille Llagostera, Mathilde Gautier, Stephane Supiot Radiation oncology, ICO, Nantes, France Purpose/Objective: Alopecia following craniospinal irradiation (CSI) has a major psychosocial impact, especially in pediatric and young adult populations. Despite its clinical Digital Poster 4838
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