VP61.01: MRI versus ultrasound expert evaluation for detecting malignancy in adnexal masses classified as inconclusive by IOTA Simple Rules

To compare diagnostic performance of MRI and ultrasound assessment performed by an expert examiner for discriminating benign from malignant masses classified as inconclusive by IOTA Simple Rules (SR). This is an ongoing single centre prospective study performed between January 2018 and January 2020. All women with an adnexal mass classified as inconclusive according to IOTA SR by non-expert examiners were submitted to MRI and ultrasound expert evaluation. MRI assessment was done according to AdnexMR score by an expert radiologist. AdnexMR score 4 (indeterminate mass) was considered as malignant for analytical purposes. Ultrasound assessment as based on examiner's subjective impression (masses were classifed as malignant, bening or indeterminate. Indeterminate mass was considered when the ultrasound examiner cannot provide a clear diagnosis (benign or malignant) with enough confidence). Reference standard was histology (patient was submitted to surgery if any of the tests was suspicious) or follow-up (Masses with > 12 months and no signs of malignancy were considered as benign). Sensitivity, specificity, positive (PLR) and negative likelihood (NLR) ratios and accuracy were calculated. Sensitivity and specificity were compared using McNemar test. During study period 54 patients were recruited. Eleven masses were malignant and 43 masses were benign. Indeterminate cases by MRI and ultrasound were 13 (24.2%) and 3 (3.8%), respectively (p < 0.01). Sensitivity, specificity, PLR, NLR and accuracy for MRI were 100%, 72%, 3.6, 0.0 and 78%, respectively. Sensitivity, specificity, PLR, NLR and accuracy for ultrasound were 91%, 88%, 7.6, 0.1 and 94%, respectively. There was a trend to better specificity in terms of specificity (p = 0.96). Albeit no statistical differences were detected ultrasound seems to be more specific and provide less indeterminate cases than MRI in inconclusive masses as determined by IOTA Simple Rules.