ESTRO 2024 - Abstract Book

S3694

Physics - Dose prediction, optimisation and applications of photon and electron planning

ESTRO 2024

For cases without and with pathological LNs, the mean difference in D95% to the tumor related and elective nodal PTV receiving 45 Gy was 0.1 Gy. Considering the pathological LN PTVs, the D95% was similar for the clinical and auto plans, with the greatest mean difference being 0.4 Gy. The D1% for the tumor related and elective nodal PTV was in average 0.5 Gy higher for the auto plans. For the bladder, all DVH parameters, except D1%, were significantly lower for the auto plans (two-sided t-test, p value<0.05). For cases without pathological LNs, the D50% to the bowel was lower for the auto plans (mean value: 18.2 Gy vs 15.9 Gy, p-value=0.06). For cases with pathological LNs, the D50% to the bowel was significantly lower for the auto plans (mean value: 17.6 Gy vs 14.2 Gy, p-value=0.002). However, for the pelvic bone the D50% was significantly higher for the auto plans, both for cases without and with pathological LNs (mean value: 27.7 Gy vs 30.6 Gy and 27.3 vs 31.1 Gy, respectively). When looking at the sacrum alone this was (mean) 33.6 Gy vs 36.1 Gy and 32.2 vs 35.8 Gy, for cases without and with pathological LNs, respectively. Figure 1a) shows box plots of V40Gy and V30Gy for the bladder, rectum and sigmoid for cases without pathological LNs when comparing the clinical plan and the auto plan (n=7). Figure 1b) shows the corresponding for cases with pathological LNs (n=7). Figure 1c) shows a clinical plan and an auto plan for the same patient, illustrating a lower dose to the bowel at the expense of conformity and dose to the sacrum.