OC04.02: Prediction of non‐resectability in ovarian cancer using the predictive index value score: a prospective multicentre study using imaging (ISAAC study)

A laparoscopy-based scoring system was developed by Fagotti (Predictive Index Value score, PIV) based on the intraoperative presence or absence of carcinomatosis on predefined sites. This model is a reference test to predict non-resectability in many institutions. The aim of the study was to analyse the performance of the PIV score calculated at ultrasound (US), contrast-enhanced computed tomography (CT), Whole-Body Magnetic Resonance Imaging with Diffusion-Weighted Sequence (WB-DWI/MRI), and during surgery in predicting non-resectability in patients with suspected tubo-ovarian cancer with reference standard (surgical outcome). This is a prospective multicentre observational study conducted between 2018 and 2022 in five European gynecological oncology centres. Patients with suspected tubo-ovarian cancer underwent prediction of non-resectability according to the PIV score, with US, CT and WB-DWI/MRI. The PIV score ranges from 0 to 12 according to the presence of disease in six predefined intra-abdominal sites (great omentum, liver surface, lesser omentum/stomach/spleen, parietal peritoneum, diaphragms, bowel serosa). The predictors of non-resectability were suspicious mesenteral retraction or miliary carcinomatosis of the small bowel (absolute criteria of non-resectability) or a PIV score>8 and the reference standard was surgical outcome (residual disease>1cm). The area under the receiver operating characteristic curve (AUC) to assess the performance of the methods in predicting non-resectability was reported. Data of 242 patients were analysed, all 3 imaging methods were performed in 182 and performance was calculated in 167. The imaging methods had similar performance in predicting non-resectable tumour (AUC = 0.80 for US, 0.75 for CT, 0.70 for WB-DWI/MRI and 0.90 for surgical exploration). US can be used as an alternative imaging method to MRI or CT in the prediction of resectability when performed by experienced examiners in dedicated oncological centres.