ESTRO 2024 - Abstract Book

S4020

Physics - Inter-fraction motion management and offline adaptive radiotherapy

ESTRO 2024

ensure required CTV coverage, the accumulated and fraction doses for the 5mm and 2mm plans were compared. Adaption criteria was defined as intervention required when D98%,CTV < 95%. The average delivered dose to OAR and the D98%,CTV for the 5mm and 2mm plan were compared using Wilcoxon signed rank test.

Results:

The daily dose to 98% of the CTV (D98%,CTV) was greater than 95% in 883 and 825 out of the total 895 fractions for the 5mm and 2mm plans respectively (Figure 1). The accumulated delivered dose D98%,CTV was less than 95% in only two cases for both 5mm and 2mm plans. No significant difference in the D98%,CTV was observed between the accumulated 2mm and 5mm plans (p=0.81). For the 5mm and 2mm daily plans, 1.3% and 7.8% of fractions showed D98%,CTV<95%, respectively (Figure 2). In adapted plans, all fractions had D98%,CTV>95%. Only insignificant dose-differences were found to OARs for ART and no-ART 5mm plans. Significant differences in the average dose to OAR were however observed between accumulated 2mm and 5mm plans. The 2mm plans exhibited mean (range) reductions of 4.1 (0.7-7.3) Gy for parotid, 2.6 (0-6.4) Gy for submandibular, 3.3 (0.3-6.5) Gy for oral cavity, 4.0 (0-12.8) Gy for esophagus, and 3.8 (0-11.5) Gy for larynx (p<0.001 for each OAR).