ESTRO 2024 - Abstract Book

S2138

Clinical - Upper GI

ESTRO 2024

Results:

Between August 2017 and March 2019, 26 patients with 45 CRLM were treated in 28 sessions with HDR-BT (Patient and treatment characteristics are presented in Table 1 ). Virtual SF MR-guided SBRT plans were generated. Median GTV BT was 3.8 cm 3 (range: 0.1 – 92.6 cm 3 ) and median PTV SBRT was 15.5 cm 3 (range: 2.7 – 164.2 cm 3 ). No significant difference was found between mean GTV D 98% in BT vs. SBRT plans (28.8 ± 2.6 Gy vs. 28.9 ± 0.9 Gy, p = 0.9), while mean GTV coverage by the prescribed dose, GTV V 25Gy , was similarly high in BT vs. SBRT plans with 100.2 ± 1.5% vs. 100.0 ± 0.1% (p < 0.05). Mean PTV SBRT V 25Gy was 98.15 ± 0.6%. GTV D 95% and D 50% were higher in BT vs. SBRT plans with GTV D 95% 31.6 ± 3.2 Gy vs. 29.2 ± 0.7 Gy (p < 0.05) and GTV D 50% 64.7 ± 12.8 Gy vs. 30.2 ± 0.5 Gy, (p < 0.001). In SBRT plans, mean PTV D 98% , D 95% , D 50% and D 2% were 25.0 ± 0.3 Gy, 25.7 ± 0.3 Gy, 29.1 ± 0.5 Gy, and 31.0 ± 0.4 Gy, respectively ( Table 2 ). Furthermore, uninvolved liver (liver - GTV) parameters were significantly higher, however within acceptable dose constraints in SBRT vs. BT plans ( Table 2 ). A median absolute difference in uninvolved liver V 5Gy of 83.7 cm 3 (range: - 136.4 - 314.3 cm 3 , p < 0.01) and smaller relative differences in V 10Gy , V 9.1Gy , V 11Gy , and V 11.6Gy : median 1.5%, 1.5%, 1.1%, and 1.0% (as percentage of total uninvolved liver volume) in SBRT vs. BT (all p < 0.01) were observed. In both BT and SBRT plans, there was only one case of a liver constraint violation in a plan comprising five GTVs. There were no significant plan violations and no significant differences between SBRT vs. BT plans vis-à-vis other OAR constraints.