Comparison of risk of malignancy indices in evaluating ovarian masses in a Southeast Asian population

INTRODUCTION The risk of malignancy index (RMI) is a scoring system used to triage benign from malignant ovarian masses. We compared the specificity and sensitivity of the four indices (RMI 1, RMI 2, RMI 3 and RMI 4) to discriminate a benign ovarian mass from a malignant one in a Southeast Asian population. METHODS This was a five-year retrospective study of women who were admitted for surgery due to ovarian masses. RMI scores were calculated based on standardised preoperative cancer antigen (CA)-125 levels, ultrasonography findings, menopausal status and tumour size based on ultrasonography. Postoperative histopathologic diagnosis was regarded as the definite outcome. Data were analysed using the Statistical Package for the Social Sciences, and Mann-Whitney U test was used to compare the individual RMI scores between the benign and malignant cases. RESULTS Out of the 480 patients reviewed, 228 women aged 10-65 years were included in the study. Of these, 17 (7.5%) had malignant disease and 211 (92.5%) had benign pathology. There was no statistical difference in the RMI 1, 2, 3 and 4 scores between the benign and malignant cases. Individual variables that were analysed showed significant differences in median CA-125 level and tumour size (p = 0.044 and p < 0.0005, respectively) between the benign and malignant cases. CONCLUSION Our study shows that RMI is not a valuable triage tool for our Southeast Asian population. Further prospective validation, with regard to standardising results in different patient populations and centres, is required.