S2800
RTT - RTT contouring, target definition, and treatment planning
ESTRO 2026
range overshoot scenarios were evaluated on the planning CT, undershoot scenarios on the override CT. To assess this technique, the dosimetric impact of our protocol was simulated by generating additional proton plans, simulating the absence of the TE by overriding all TE components with adipose tissue. The standard treatment planning protocol was then applied for these simulations. Reference photon plans for the same patients were obtained from the referring hospital. Target coverage, mean heart, lung and contralateral breast doses were evaluated for proton, simulated proton, and photon plans. Results: A total of 15 radiotherapy courses for 13 patients were evaluated; 13 were delivered with PT and two with photon therapy. Clinical goals on target coverage were met in 11/15 proton, 12/15 simulated, and 9/15 photon plans. For all OOIs, mean doses to the heart, lungs, and contralateral breast were lowest in the simulated plans and highest in the photon plans (Figure 1).
local control and favorable toxicity profile. Oral Oncology. April 2022; 10.1016/j.oraloncology.2022.105782 Keywords: single vocal cord, VMAT, IMRT
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IMPT for breast cancer patients with tissue expanders: evaluation of treatment planning technique Jenneke J. Jacobs 1 , Esther Gagesteijn 1 , Myra Rodrigues 1 , Sophie C.J. Bosma 2 , Anna L. Petoukhova 3 , Quinten Telkamp 1,4 , Margriet G.A. Sattler 1,5 , Yvonne L.B. Klaver 1,2 , Steven J.M. Habraken 1,2 1 Radiotherapy, Holland Proton Therapy Center, Delft, Netherlands. 2 Radiotherapy, Leiden University Medical Netherlands. 4 Radiotherapy, NKI_AVL, Amsterdam, Netherlands. 5 Radiotherapy, Erasmus Medical Center, Rotterdam, Netherlands Purpose/Objective: Postmastectomy radiotherapy (PMRT) reduces the risk of recurrence and breast cancer (BC) related mortality in selected patients [1]. An increasing number of patients choose to undergo breast reconstruction (immediate or delayed) after mastectomy. Immediate breast reconstruction after mastectomy offers better patient-reported cosmetic outcomes and shorter overall treatment time compared to delayed reconstruction [2]. However, PMRT with a tissue expander (TE) in situ is associated with poorer cosmetic outcomes and higher complication rates [3]. Center, Leiden, Netherlands. 3 Radiotherapy, Haaglanden Medical Center, Leidschendam, Since 2019, proton therapy (PT) is available for selected BC patients in the Netherlands [4]. TEs contain high-density, metal-containing valves, introducing significant dosimetric uncertainties in PT. To address this, we have developed and implemented a dedicated treatment planning protocol. However, we hypothesize that this approach comes with trade-offs regarding dose to organs of interest (OOIs). Here, we report the evaluation of this treatment planning protocol. Material/Methods: Patients who underwent mastectomy with immediate reconstruction with a TE, referred to HollandPTC for a plan comparison were included. PT plans were optimized using two CT scans, planning and override, with identical structures. Density overrides were applied to TE components on both scans; the metallic valve was overridden only on the override CT. Robust optimization included 5mm isotropic setup and 3% range uncertainty. A dedicated script was developed for robust evaluation using the same parameters;
Conclusion: Our treatment planning technique, using two CTs during optimization, is clinically feasible; however resulting in higher OOI doses compared to simulations. Despite increased OOI doses, dosimetric advantage of proton over photon therapy remains for individual patients. References: 1. McGale P, et al. Effect of radiotherapy after mastectomy and axillary surgery on 10-year recurrence and 20-year breast cancer mortality. Lancet 2014;383:2127–35.2. van Bommel A, et al. The added value of immediate breast reconstruction to
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