ESTRO 2021 Abstract Book

S356

ESTRO 2021

identification/elimination criteria, internal validation were previously agreed with the coordinating center. The resulting models were then imported into a dedicated Eclipse research station (V.16.7) and tested on 12 additional pts avaiable from six of the involved Institutes (2 pts per Institute). At the time of current analysis, five models were available, while two were still ongoing. DVH prediction bands of OARs (heart, ipsilateral lung, contralateral lung, contralateral breast) were analyzed. Inter-institute variability of plan performances was assessed by considering predicted DVH averaged with respect to Institutes and their (inter-institute) SD. Results Predicted DVH (normalized to the 40Gy/15 fraction scheme), calculated as the mean between DVH min and DVH max , showed relatively good consistency, despite some not negligible inter-institute variability was seen: in Figure 1, mean DVHs of right lung (over all 12 patients) are shown for the five models with the average value incorporating inter-institute variability. As an example, V20 mean value for ipsilateral lung was 11.3% and inter-institute SD was 1.5%. Mean doses of OARs for all institutes and their mean and SD (quantifying inter- institute variability) are shown in Table1: as expected, inter-institute variability for contralateral OARs was very small (within 0.17Gy), while inter-institute SD for ipsilateral lung was 0.36 Gy with mean institutional values ranging between 5.1 and 6.1 Gy.

Fig.1

Tab.1

Conclusion These preliminary results quantify for the first time inter-institute variability of DVH prediction models in the case of WB TF. Results are encouraging showing clear potentials for efficient incorporation of inter-institute variability on KB-model and/or benchmarking. The extension to more models and more patients, to better refine the results is warranted. This study is supported by an AIRC grant (IG23150).

OC-0470 Development and validation of an automated robust treatment planning method for lung proton therapy