ESTRO 2024 - Abstract Book

S2221

Clinical - Upper GI

ESTRO 2024

To our knowledge, this is the first study to evaluate spleen dose, VB dose, and other factors associated with post treatment lymphopenia after 5-fraction A-RT for inoperable PDAC. Despite the ablative prescription dose and routine treatment of elective regions we observed a low incidence of >G2L that was similar compared to prior 5 fraction NA-RT studies. Spleen and VB doses were not significantly associated with >G2L in our analysis and this might be related to spleen dose being especially low for most patients because of posterolateral beam avoidance. We are currently evaluating whether >G2L lymphopenia is associated with long-term clinical outcomes in this patient cohort.

Keywords: ablative radiation, pancreas cancer, lymphopenia

2059

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Interobserver variability in pancreatic cancer delineation between the arterial and venous phases

Fabien Zaidi 1 , Paul Calame 2 , Cédric Chevalier 1 , Julie Henriques 3 , Vuitton Lucine 4 , Bruno Heyd 5 , Christophe Borg 6 , Jihane Boustani 1 1 University of Bourgogne Franche-Comté, CHU Besançon, Radiotherapy, Besançon, France. 2 University of Bourgogne Franche-Comté, CHU Besançon, Radiology, Besançon, France. 3 University of Bourgogne Franche-Comté, CHU Besançon, Methodology and Quality of Life Unit in Oncology, Besançon, France. 4 University of Bourgogne Franche Comté, CHU Besançon, Gastroenterology, Besançon, France. 5 University of Bourgogne Franche-Comté, CHU Besançon, Digestive surgery, Besançon, France. 6 University of Bourgogne Franche-Comté, CHU Besançon, Oncology, Besançon, France

Purpose/Objective:

The planification of radiation therapy (RT) for pancreatic cancer (PC) requires a dosimetric computed tomography (CT) scan with intravenous (IV) contrast to define the gross tumor volume (GTV). The main objective of this study was to compare the inter-observer variability in RT planning between the arterial and the venous phases.

Material/Methods:

This was a prospective monocentric study that included twenty patients with non-metastatic PC. Patients underwent pre-therapeutic CT scans at the arterial and venous phases. The delineation of the GTV was performed by one radiologist specialized in pancreatic imaging (gold standard), and two senior radiation oncologists (operators). Observers were blinded to each other during the process. The primary endpoint was the Jaccard conformity index (JCI) for the GTVs at the arterial and the venous phases between the gs and the operators. The secondary end points were the geographical miss index (GMI), the kappa index, the intra-operator variability, and the dose-volume histograms between the arterial and venous phases.