ESTRO 2025 - Abstract Book

S3917

Radiobiology - Normal tissue radiobiology

ESTRO 2025

Telangiectasia after Radiotherapy in 272 Breast Cancer Patients with >10-Year Follow-up. Clin Cancer Res. 2019 Jan 15;25(2):562-572. 2. Herskind C, Sticht C, Sami A, Giordano FA, Wenz F. Gene Expression Profiles Reveal Extracellular Matrix and Inflammatory Signaling in Radiation-Induced Premature Differentiation of Human Fibroblast in vitro. Front Cell Dev Biol. 2021 Feb 18;9:539893.

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Digital Poster hippocampal dose exposure in nasopharyngeal cancer patients treated with modulated volumetric arc therapy (vmat) Yasmine Daghfous 1 , hajjer jaffel 1 , takoua ben dhif 1 , semia ben hassine 1 , radhouen braiki 1 , manel arfaoui 1 , wiem abid 1 , najet mahjoub 2 1 radiotherapy, Regional cancer center, jendouba, Tunisia. 2 chemotherapy, Regional cancer center, jendouba, Tunisia Purpose/Objective: This study assesses the incidental hippocampal dose exposure in nasopharyngeal cancer (NPC) patients treated with volumetric modulated arc therapy (VMAT) at the oncology center of Jendouba, Tunisia, (2020 to 2023) Material/Methods: A retrospective analysis was conducted on dosimetric data from 36 NPC patients, with a mean age of 50.94 years. Of these, 20% were in early-stage (T1-T2), and 80% in advanced stages (T3-T4). Node involvement was present in 67% of patients, while endocranial extension was noted in 16.7% and optic nerve involvement in 2.8%. All patients received a total dose of 69.96 Gy in 33 fractions to the high-risk planning target volume (PTV), with a simultaneous integrated boost to the intermediate-risk PTV using a double arc technique. Hippocampal volumes were delineated on simulation CT scans fused with MRI, starting from the anterior portion of the lateral ventricle. Treatment plans were created without specific dose-volume constraints for the hippocampus. The following dosimetric parameters were studied: mean hippocampal volume, Dmean, Dmin, D0.03, D40%, V20, V40, and V60. Results: The mean hippocampal volume was 4.22 cm³ [1.42–6.75 cm³]. The Dmean was 16.15 Gy [ 4.07–35.22 Gy], and the Dmin was 4.55 Gy [1.61–10.37 Gy]. The dose to 0.03 cm³ (D0.03) was 39.52 Gy [14.50–69.62 Gy], while the dose received by 40% of the hippocampal volume (D40%) was 15.70 Gy [2.05–43.16 Gy] . The percentage of hippocampal volume receiving 20% of the prescribed dose (V20) was 27.64% [0.00–89.91%] , corresponding to a mean volume of 2.07 cm³ [ 0.00–31.09 cm³]. For the 40% dose (V40), 4.38% of the hippocampal volume was exposed [0.00–40.05%] , or 0.49 cm³ [0.00–7.49 cm³] . The exposure to 60% of the prescribed dose (V60) was minimal, averaging 0.02% [0.00–0.22%] . Among patients with endocranial extension (16.7% of the cohort), the D0.03 was higher, with a mean of 41.03 Gy (range: 24.03–63.93 Gy). Conclusion: This study demonstrates significant incidental hippocampal dose exposure in VMAT treatment plans for NPC, particularly with D0.03 [14.50–69.62 Gy] and D40% [2.05–43.16 Gy]. Patients with endocranial extension received higher doses, with D0.03 ranging from 24.03 to 63.93 Gy. These results underscore the need for delineation guidelines and dose constraints for the hippocampus in NPC treatment and advocate for hippocampal sparing techniques to minimize potential long-term neurocognitive side effects.

Keywords: Hippocampus,VMAT,nasopharynx