OC04.03: Preoperative assessment of non‐resectability in ovarian cancer according to ESGO criteria: a prospective multicentre study using imaging (ISAAC study)

The aim of the study was to test the non-inferiority of abdominopelvic ultrasound compared to computed tomography (CT) and whole-body diffusion-weighted Magnetic Resonance Imaging (WB-DWI/MRI) in prediction of surgical outcome in patients with tubo-ovarian cancer. This is a multicentric prospective study (ISAAC study, Imaging Study on Advanced ovArian Cancer) conducted between 2018 and 2022 in five European gynecological oncology centres. Patients with suspected tubo-ovarian cancer planned for surgery underwent preoperative prediction of non-resectability with ultrasound, CT and WB-DWI/MRI. The prediction of non-resectability was based on the European Society of Gynecologic Oncology (ESGO) criteria of non-resectability. Findings were compared to the reference standard (surgical outcome). The area under the receiver operating characteristic curve (AUC) to assess the performance of the methods in predicting non-resectability was reported. Concordance between ultrasound, CT and WB-DWI/MRI and intraoperative parameters was calculated using Cohen's kappa. Data of 242 patients were analysed, all 3 imaging methods were performed in 182. Performance was calculated in a cohort of 167 patients. The AUC was 0.83 for ultrasound, 0.75 for CT, 0.72 for WB-DWI/MRI and 0.95 for explorative surgery. Ultrasound was non-inferior to CT (p = 0.006) and MRI (p < 0.001) in the prediction of non-resectability using ESGO criteria. Agreement between ultrasound and surgical findings had the highest Cohen's κ for all ESGO criteria (ranging from 0.67 to -0.011), but it was good only for one parameter (mesenteric root). The agreement between CT and surgical findings and between WB-DWI/MRI and surgical findings were poor to fair for all parameters. Ultrasound is not inferior to CT and WB-DWI/MRI in predicting the non-resectability in patients with tubo-ovarian cancer when performed by experienced examiners.