Comparative performance of four risk of malignancy indices (RMI) in predicting ovarian malignancy: a large retrospective cohort study

Abstract

OBJECTIVES: To compare the predictive performance of four risk of malignancy index (RMI) in patients with adnexal masses. MATERIAL AND METHODS: This retrospective study included 703 patients who underwent surgery for adnexal masses. Preoperative ultrasonographic findings, menopausal status, and serum CA-125 levels were used to calculate RMI-1, -2, -3, and -4. Histopathology served as the reference standard. Sensitivity, specificity, positive and negative predictive values, and overall accuracy were analyzed. RESULTS: Among 703 patients, 77.2% had benign lesions, 3.3% borderline tumors, and 19.5% malignant disease. RMI-1 demonstrated sensitivity 74.4%, specificity 91.3%, PPV 71.7%, NPV 92.4%; RMI-2 sensitivity 80.6%, specificity 86.2%, PPV 63.2%, NPV 93.8%; RMI-3 sensitivity 75.6%, specificity 90.1%, PPV 69.1%, NPV 92.6%; and RMI-4 sensitivity 78.8%, specificity 89.9%, PPV 69.6%, NPV 93.5%. ROC analysis showed areas under the curve of 0.900, 0.896, 0.893, and 0.893 for RMI-1 to RMI-4, respectively. RMI-1 had the highest specificity and overall accuracy, whereas RMI-2 achieved the highest sensitivity. Pairwise comparisons revealed statistically significant differences among RMIs. CONCLUSIONS: All four RMIs effectively differentiate benign from malignant adnexal masses. RMI-1 offers the highest overall accuracy and specificity, and RMI-2 the highest sensitivity. These indices provide valuable preoperative risk stratification to guide clinical management and referral to specialized care. Institutional resources should inform the choice of RMI.