S2024
Physics - Dose prediction/calculation, optimisation and applications for photon and electron planning
ESTRO 2026
median of 68 Gy10 within VTC. Goals for OOI per EMBRACE II EBRT protocol were achieved as demonstrated in Figure 1. Brachytherapy-related doses (median) for OOI were provided in Figure 2. D5cc/2cc/0.1cc for bladder were 47/48/53Gy3, rectum 44/45/48Gy3, sigmoid 42/43/45Gy3, and bowel43/44/48Gy3. The trend of lower doses to Organs* were observe without large difference in Bladder-Bladder* and Rectum-Rectum* D2cc and D5cc.
Radiation Physics, University of Texas MD Anderson Cancer Center, Houston, Tx, USA. 6 Department of Radiation Oncology, University of Texas MD Anderson Cancer Center, Houston,Tx, USA. 7 Department of Radiation Oncology, University of Texas MD Anderson Cancer Center, Houston, Tx, USA Purpose/Objective: To evaluate a novel upfront "Brachy-like" SBRT technique delivering aimed to enhance tumor reduction and immunopotentiation before definitive chemoradiation and brachytherapy (1–3). Spatial dose summation with VMAT 40Gy/20F was explored, accounting for potential EBRT-Brachytherapy overlapped dose. Material/Methods: Ten cervical-cancer patients in Thai-single center were retrospectively re-optimized on the same initial planning CT. “Brachy-like” SBRT was planned on Monaco TPS to deliver high dose 16Gy/2F to “Virtual- tandem core PTV (VTC-PTV; a core of HR-CTV)” and 7Gy/2F to HR-CTV on 1.5T MR-linac. 12-beam gantry angles were arranged with isocenter at the center of the HR-CTV. Stringent limits for the bladder (D2cc<5Gy) and rectal/sigmoid (D2cc<4Gy) was limited. All plans underwent patient-specific quality assurance (PSQA) using an ArcCheck phantom and 3%/2mm gamma analysis.The 2-arc VMAT was planned on RayStation for 40Gy/20F with SIB to 53/55Gy to gross lymph nodes. Spatial dose summation with Brachy-like SBRT was performed on the same CT with multi-TPS workflow on RayStation. Tumor target volume and organ of interest (OOI) EQD2 doses were collected according to ratio of 10 and 3 Gy, respectively. Organs* was generated as the intercepted volume of OOI and 2-cm isotropic expansion of HR-CTV achieve more accurate potential EBRT-Brachy-overlapped dose measurement. Results: Ten patients (7 T2b and 3 T3b stages) harbored a median tumor diameter of 6 cm (IQR,5.4-6.6) and initial HR-CTV of 82 cc (IQR,52-98). All were dosimetrically feasible and clinically acceptable (Figure1). Median D90%/D50%/Dmax VCT- PTV were 15.3/16.5/17.9 Gy and HR-CTV were 5.6/6.9/9.8 Gy, respectively. Sparing of OOI was successful, with median Bladder D0.03cc/D2cc were 6.2/5.3 Gy, Rectum 4.9/3.5 Gy, and Sigmoid 2.0/0.8 Gy, respectively. Plans demonstrated efficient delivery characteristics with a median of 94.5 segments (IQR,91.25-95.50), 2704 MU (IQR,2468-2778), and an estimated delivery time of 9.0 minutes (IQR,8.7-9.5). Plans achieved a median gamma passing rate of 95.9 (IQR,94.2-97.1).For summative dose, clinical target achieved median D50/90/98% of HR-CTV at 53/49/47Gy10 and VTC-PTV for 66/64/62Gy10. The maximum dose point achieved
Made with FlippingBook - Share PDF online