External validation of the IOTA two-step strategy in the preoperative characterization of ovarian masses

Preoperative sonographic evaluation of ovarian masses is crucial for improving outcomes. The Risk of Malignancy Index (RMI) has been a standard for malignancy triage, while the International Ovarian Tumor Analysis Group (IOTA) has proposed a two-step strategy to estimate the risk of malignancy and suggest management steps by translating risks to Ovarian Adnexal Reporting Data System (O-RADS) categories. This study compares the accuracy of RMI and the IOTA two-step strategy in predicting malignancy.

We included patients with preoperative ultrasound and pathological reports. RMI and O-RADS scores based on the IOTA two-step strategy were assessed. Performance was evaluated using receiver operating characteristic (ROC) curves and calibration plots.

A total of 453 cases were included. Of these, 90 (19.9 %) were malignant, 21 (4.6 %) were borderline tumors (BOT), and 342 (75.5 %) were benign. The area under the ROC curve (AUC) for the IOTA two-step strategy was 0.958 (95 % CI, 0.938-0.978), compared to 0.904 (0.865-0.943) for RMI with a > 200 cut-off. The IOTA two-step strategy had a sensitivity of 96.4 %, specificity of 79.7 %, positive predictive value (PPV) 60.2 %, and negative predictive value (NPV) 98.6 %, while RMI showed sensitivity of 70.4 %, specificity 93.4 %, PPV 79.2 %, and NPV 89.8 %. For predicting BOTs, the IOTA two-step AUC was 0.902, compared to 0.719 for RMI.

The IOTA two-step strategy outperforms RMI in the preoperative assessment of adnexal masses, particularly in detecting BOTs. It should be implemented in routine clinical practice.