Validation of a second-generation multivariate index assay for malignancy risk of adnexal masses

Abstract

Women with adnexal mass suspected of ovarian malignancy are likely to benefit from consultation with a gynecologic oncologist, but imaging and biomarker tools to ensure this referral show low sensitivity and may miss cancer at critical stages. The multivariate index assay (MIA) was designed to improve the detection of ovarian cancer among women undergoing surgery for a pelvic mass. To improve the prediction of benign masses, we undertook the redesign and validation of a second-generation MIA (MIA2G). MIA2G was developed using banked serum samples from a previously published prospective, multisite registry of patients who underwent surgery to remove an adnexal mass. Clinical validity was then established using banked serum samples from the OVA500 trial, a second prospective cohort of adnexal surgery patients. Based on the final pathology results of the OVA500 trial, this intended-use population for MIA2G testing was high risk, with an observed cancer prevalence of 18.7% (92/493). Coded samples were assayed for MIA2G biomarkers by an external clinical laboratory. Then MIA2G results were calculated and submitted to a clinical statistics contract organization for decoding and comparison to MIA results for each subject. Sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) were calculated, among other measures, and stratified by menopausal status, stage, and histologic subtype. Three MIA markers (cancer antigen 125, transferrin, and apolipoprotein A-1) and 2 new biomarkers (follicle-stimulating hormone and human epididymis protein 4) were included in MIA2G. A single cut-off separated high and low risk of malignancy regardless of patient menopausal status, eliminating potential for confusion or error. MIA2G specificity (69%, 277/401 [n/N]; 95% confidence interval [CI], 64.4-73.4%) and PPV (40%, 84/208; 95% CI, 33.9-47.2%) were significantly improved over MIA (specificity, 54%, 215/401; 95% CI, 48.7-58.4%, and PPV, 31%, 85/271; 95% CI, 26.1-37.1%, respectively) in this cohort. Sensitivity and NPV were not significantly different between the 2 tests. When combined with physician assessment, MIA2G correctly identified 75% of the malignancies missed by physician assessment alone. MIA2G specificity and PPV were significantly improved compared with MIA, while sensitivity and NPV were unchanged. The second-generation test significantly improved the predicted efficiency of triage vs MIA without sacrificing high sensitivity and NPV, which are essential for effectiveness.