Interobserver variation in tumor delineation of liver metastases using Magnetic Resonance Imaging

• DOI: 10.1016/j.phro.2024.100592
• Publication Date: 2024-05-27T23:40:52Z
• Authors: Julia E. Peltenburg; Ali Hosni; Rana Bahij; Simon Boeke; Pètra M. Braam; William A. Hall; Martijn P.W. Intven; Luca Nicosia; Jan-Jakob Sonke; Marnix Witte; Marlies E. Nowee; Tomas Janssen
• Keywords: Radiation; GTV; Interobserver variation (IOV); R895-920; Neoplasms. Tumors. Oncology. Including cancer and carcinogens; Quality assurance (QA); Liver metastases; Medical physics. Medical radiology. Nuclear medicine; 03 medical and health sciences; 0302 clinical medicine; Oncology; Radiology Nuclear Medicine and imaging; Radiation Oncology - Radboud University Medical Center; Original Research Article; Tumor delineation; RC254-282; MRI

Magnetic Resonance Imaging (MRI) guided stereotactic body radiotherapy (SBRT) of liver metastases is an upcoming high-precision non-invasive treatment. Interobserver variation (IOV) in tumor delineation, however, remains a relevant uncertainty for planning target volume (PTV) margins. The aims of this study were to quantify IOV in MRI-based delineation of the gross tumor volume (GTV) of liver metastases and to detect patient-specific factors influencing IOV.A total of 22 patients with liver metastases from three primary tumor origins were selected (colorectal(8), breast(6), lung(8)). Delineation guidelines and planning MRI-scans were provided to eight radiation oncologists who delineated all GTVs. All delineations were centrally peer reviewed to identify outliers not meeting the guidelines. Analyses were performed both in- and excluding outliers. IOV was quantified as the standard deviation (SD) of the perpendicular distance of each observer's delineation towards the median delineation. The correlation of IOV with shape regularity, tumor origin and volume was determined.Including all delineations, average IOV was 1.6 mm (range 0.6-3.3 mm). From 160 delineations, in total fourteen single delineations were marked as outliers after peer review. After excluding outliers, the average IOV was 1.3 mm (range 0.6-2.3 mm). There was no significant correlation between IOV and tumor origin or volume. However, there was a significant correlation between IOV and regularity (Spearman's ρs = -0.66; p = 0.002).MRI-based IOV in tumor delineation of liver metastases was 1.3-1.6 mm, from which PTV margins for IOV can be calculated. Tumor regularity and IOV were significantly correlated, potentially allowing for patient-specific margin calculation.