Knopf, Antje

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Knopf
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Antje
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Knopf, Antje

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20222
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Autor:in: Both, Stefan × Autor:in: Korevaar, Erik W. ×

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    Publikation
    Robustness assessment of clinical adaptive proton and photon radiotherapy for oesophageal cancer in the model-based approach
    (Elsevier, 12/2022) Visser, Sabine; O. Ribeiro, Cássia; Dieters, Margriet; Mul, Veronique E.; Niezink, Anne G.H.; van der Schaaf, Arjen; Langendijk, Johannes A.; Korevaar, Erik W.; Both, Stefan; Muijs, Christina T.; Knopf, Antje [in: Radiotherapy and Oncology]
    Purpose In the Netherlands, oesophageal cancer (EC) patients are selected for intensity modulated proton therapy (IMPT) using the expected normal tissue complication probability reduction (ΔNTCP) when treating with IMPT compared to volumetric modulated arc therapy (VMAT). In this study, we evaluate the robustness of the first EC patients treated with IMPT in our clinic in terms of target and organs-at-risk (OAR) dose with corresponding NTCP, as compared to VMAT. Materials and Methods For 20 consecutive EC patients, clinical IMPT and VMAT plans were created on the average planning 4DCT. Both plans were robustly evaluated on weekly repeated 4DCTs and if target coverage degraded, replanning was performed. Target coverage was evaluated for complete treatment trajectories with and without replanning. The planned and accumulated mean lung dose (MLD) and mean heart dose (MHD) were additionally evaluated and translated into NTCP. Results Replanning in the clinic was performed more often for IMPT (15x) than would have been needed for VMAT (8x) (p = 0.11). Both adaptive treatments would have resulted in adequate accumulated target dose coverage. Replanning in the first week of treatment had most clinical impact, as anatomical changes resulting in insufficient accumulated target coverage were already observed at this stage. No differences were found in MLD between the planned dose and the accumulated dose. Accumulated MHD differed from the planned dose (p < 0.001), but since these differences were similar for VMAT and IMPT (1.0 and 1.5 Gy, respectively), the ΔNTCP remained unchanged. Conclusion Following an adaptive clinical workflow, adequate target dose coverage and stable OAR doses with corresponding NTCPs was assured for both IMPT and VMAT.
    01A - Beitrag in wissenschaftlicher Zeitschrift
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    Publikation
    Diaphragm-based position verification to improve daily target dose coverage in proton and photon radiation therapy treatment of distal esophageal cancer
    (Elsevier, 01.02.2022) Visser, Sabine; den Otter, Lydia A.; Ribeiro, Cássia O.; Korevaar, Erik W.; Both, Stefan; Langendijk, Johannes A.; Muijs, Christina T.; Sijtsema, Nanna M.; Knopf, Antje [in: International Journal of Radiation. Oncology - Biology – Physics]
    Purpose In modern conformal radiation therapy of distal esophageal cancer, target coverage can be affected by variations in the diaphragm position. We investigated if daily position verification (PV) extended by a diaphragm position correction would optimize target dose coverage for esophageal cancer treatment. Methods and Materials For 15 esophageal cancer patients, intensity modulated proton therapy (IMPT) and volumetric modulated arc therapy (VMAT) plans were computed. Displacements of the target volume were correlated with diaphragm displacements using repeated 4-dimensional computed tomography images to determine the correction needed to account for diaphragm variations. Afterwards, target coverage was evaluated for 3 PV approaches based on: (1) bony anatomy (PV_B), (2) bony anatomy corrected for the diaphragm position (PV_BD) and (3) target volume (PV_T). Results The cranial-caudal mean target displacement was congruent with almost half of the diaphragm displacement (y = 0.459x), which was used for the diaphragm correction in PV_BD. Target dose coverage using PV_B was adequate for most patients with diaphragm displacements up till 10 mm (≥94% of the dose in 98% of the volume [D98%]). For larger displacements, the target coverage was better maintained by PV_T and PV_BD. Overall, PV_BD accounted best for target displacements, especially in combination with tissue density variations (D98%: IMPT 94% ± 5%, VMAT 96% ± 5%). Diaphragm displacements of more than 10 mm were observed in 22% of the cases. Conclusions PV_B was sufficient to achieve adequate target dose coverage in case of small deviations in diaphragm position. However, large deviations of the diaphragm were best mitigated by PV_BD. To detect the cases where target dose coverage could be compromised due to diaphragm position variations, we recommend monitoring of the diaphragm position before treatment through online imaging.
    01A - Beitrag in wissenschaftlicher Zeitschrift