Validation of ADNEX and the IOTA two-step strategy and estimation of risk of complications during follow-up of adnexal masses in a low-risk population

OBJECTIVES:The aim is to evaluate the ability of the Assessment of Different NEoplasias in the adneXa model (ADNEX) and the International Ovarian Tumour Analysis (IOTA) two-step strategy to predict malignancy in adnexal masses detected in an outpatient low-risk setting, and to estimate the risk of complications in masses with benign ultrasound morphology managed with clinical and ultrasound follow-up. METHODS:This single center (Hospital Universitari Dexeus Barcelona) study was performed using interim data of the ongoing prospective observational IOTA phase 5 study. The primary aim of the IOTA 5 study is to describe the cumulative incidence of complications during follow-up of adnexal masses classified as benign on ultrasound. Consecutive patients with adnexal masses detected between June 2012 and September 2016 in a private center offering screening for gynecological cancers were included and followed-up until February 2020. Tumors were classified as benign or malignant based on histology (if patients underwent surgery) or outcome of clinical and ultrasound follow-up at 12 (±2) months. Multiple imputation was used when follow-up information was uncertain. The ability of the ADNEX model without CA125 and of the IOTA two-step strategy to distinguish benign from malignant masses was evaluated retrospectively using the prospectively collected data. We describe performance as discrimination (area under the receiver operating characteristic curve, AUC), calibration, classification (sensitivity and specificity) and clinical utility (Net Benefit). In the group of patients with a benign looking mass selected for conservative management we evaluated the occurrence of spontaneous resolution or any mass complication during the first 5 years of follow-up by assessing the cumulative incidence for malignancy, torsion, cyst rupture, or minor mass complications (inflammation, infection, or adhesions) and the time to occurrence of an event. RESULTS:A total of 2654 patients were recruited to the study. After application of exclusion criteria, 2039 patients with a newly detected mass were included for the model validation. 1684 (82.6%) masses were benign, 49 (2.4%) masses were malignant and for 306 (15.0%) masses the outcome was uncertain and imputed. The AUC was 0.95 (95% CI 0.89-0.98) for ADNEX and 0.94 (95% CI 0.88-0.97) for the two-step strategy. Calibration performance could not be meaningfully interpreted due to few malignancies resulting in very wide confidence intervals. The two-step strategy had better clinical utility than ADNEX at malignancy risk thresholds < 3%. 1472 (72%) patients had a mass judged to be benign based on pattern recognition by an experienced ultrasound examiner and were managed with clinical and ultrasound follow-up. In this group, the 5-year cumulative incidence was 66% for spontaneous resolution of the mass (95% CI 63-69), 0% for torsion (95%CI 0-0.002), 0.1% for cyst rupture (<0.1-0.6), 0.2% for a borderline tumor (<0.1-0.6), and 0.2% (0.1-0.6) for invasive malignancy. CONCLUSIONS:The ADNEX model and IOTA two-step strategy performed well to distinguish benign from malignant adnexal masses detected in a low-risk population. Conservative management is safe for masses with benign ultrasound appearance in such a population. This article is protected by copyright. All rights reserved.