ESTRO 2025 - Abstract Book

S2883

Physics - Dose prediction, optimisation and applications of photon and electron planning

ESTRO 2025

Conclusion: DL autocontouring provided a higher consistency in CTVn contours and highly accurate OARs-delineation. Auto contours were generally more closely aligned with the experts, than experts’ contours towards themselves. Superior treatment plans quality was provided by fully automated workflow. However, this came at the expense of an increased difference in PTV coverage due to IOV.

Keywords: autosegmentation, autoplanning, head-and-neck

References: [1] Vandewinckele, L. et al. Overview of artificial intelligence-based applications in radiotherapy: Recommendations for implementation and quality assurance. Radiotherapy and Oncology, 153, 55-66 (2020). [2] Kosmin, M. et al. Rapid advances in auto-segmentation of organs at risk and target volumes in head and neck cancer. Radiotherapy and Oncology, 135, 130-140 (2019).

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Digital Poster Intensity modulated proton beam therapy in vulvar cancer: a dosimetric analysis Wiwatchai Sittiwong, Vossco Nguyen, Molly Munro, Deepali Purohit, Gemma Eminowicz, Asma Sarwar Radiotherapy, University College London Hospital, London, United Kingdom Purpose/Objective: Vulvar cancers are rare accounting for <1% of all gynaecological cancers. Primary treatment is surgery followed by adjuvant radiotherapy for patients with risk factors for recurrence. Proton beam therapy (PBT) may offer advantages in this treatment setting. However, data on its use is lacking, and the robustness of PBT for this cancer has yet to be evaluated. This study aimed to evaluate the potential treatment planning benefit and the robustness of intensity modulated proton therapy (IMPT) in vulvar cancer. Material/Methods: Five patients with locally advanced vulvar cancer, who were treated with volumetric modulated arc therapy (VMAT) were included in the study. All patients received a radiotherapy dose of 56–60.2 Gy to the primary tumour bed and 46.2–50.4 Gy to the elective nodal region, with or without a boost of 56 Gy in 28 fractions. All were replanned to create IMPT plans. Daily cone beam computed tomography (CBCT) images were reviewed and the single ‘worst-case’ scenario CBCT was selected for replan review. Dosimetric evaluation and comparison, using a statistical t-test, between VMAT, IMPT and worst-case scenario CBCT scans were performed to assess the robustness of IMPT delivery. For each plan, D0.5cc, V30Gy, V40Gy, V50Gy, V60Gy, and Dmean for the bladder, rectum, and bowel bag were compared. D0.5cc for femoral heads and D0.5cc with Dmax for the skin were also evaluated. The integral dose was compared using V5%. Results: Among the five patients, three had primary disease (FIGO stage IIIA, IIIB, and IIIC2), and two had recurrent disease. All underwent surgery as primary treatment prior to radiotherapy and were squamous cell carcinoma histology. VMAT and IMPT achieved comparable planning target volume (PTV) D95% and D98%. IMPT significantly reduced the bladder V30Gy and V40Gy as well as rectum V30Gy when compared to VMAT. No differences were observed in doses to the remaining organs at risk (OARs). For the robustness of PBT delivery, one case failed to meet the planned objectives due to changes in internal anatomy. However, comparing among 5 patients, there were no statistically significant differences in PTV coverages or OAR doses between the IMPT and IMPT worst-case scenarios.