Evaluating use of IOTA two-step strategy to classify adnexal masses identified in pregnancy: pilot study

OBJECTIVES: The primary aim was the validation of benign descriptors (BDs), followed by Assessment of Different NEoplasia's of the adneXa (ADNEX) (when BDs cannot be applied), in a two-step strategy to classify adnexal masses in pregnancy. The secondary aim was to describe the natural history of adnexal masses in pregnancy. METHODS: Retrospective analysis of prospectively collected data of women with an adnexal mass on ultrasonography identified during pregnancy between 2017 and 2022. The study was conducted at Queen Charlotte's and Chelsea Hospital, UK. Relevant clinical and ultrasound data were extracted from the medical records and ultrasound software astraia. Adnexal masses were classified and managed according to expert subjective assessment (SA). Ultrasound features were recorded prospectively at the time of ultrasound examination. Borderline ovarian tumours (BOT) were classified as malignant. Benign Descriptors (BDs) were applied to classify adnexal masses, in cases where BDs were not applicable, the ADNEX model (using a risk of malignancy of >10%) was used, in a two-step strategy. The two-step strategy was applied retrospectively. The reference standard used was histology (where available) or expert SA at the postnatal ultrasound scan. RESULTS: 291 women with a median age of 33 (IQR 29-36) years presented with an adnexal mass in pregnancy, at a median gestation of 12 (IQR 8-17) weeks. 267 (267/291, 91.8%) women were followed up to the postnatal period, as 24 women (24/291, 8.2%) were lost to follow up. Based on the reference standard, 4.1% of adnexal masses (11/267) were classified as malignant (all BOTs) and 95.9% (256/267) as benign (41 on histology and 215 based on expert SA at postnatal ultrasound). BDs could be applied to 68.9% of adnexal masses (184/267); of these only one mass (BOT) was misclassified as benign (1/184, 0.5%). ADNEX was used to classify the residual masses (83/267) and misclassified three BOTs as benign (3/10, 30.0%) and 25 benign masses (based on reference standard) as malignant (25/73, 34.2%), 13 (13/25, 52.0%) of these were classified as decidualised endometriomas on expert SA, with confirmed resolution of decidualisation in the postnatal period. The two-step strategy had a specificity of 90.2%, sensitivity of 63.6%, negative predictive value of 98.3% and positive predictive value of 21.9%. 56 (56/267, 21.0%) women had surgical intervention, four as an emergency during pregnancy (4/267, 1.5%,) and four (4/267, 1.5%) electiv