Background: Concomitant with the development of in vitro diagnostic multivariate index assays (IVDMIAs) to improve the diagnostic efficiency of ovarian cancer detection is the need to identify appropriate biostatistical approaches to assess improvements in risk predication. In this study, we assessed the utility of three different approaches for comparing diagnostic efficiency of an ovarian cancer multivariate assay in a retrospective case--control phase 2 biomarker trial. The control cohort included both disease-free women and women with benign gynecological conditions to more accurately reflect the target population of symptomatic women.
Methods: The study cohort comprised plasma samples from 244 healthy controls, 223 women with benign gynecological conditions, 53 borderline ovarian cancer cases and 222 women with malignant epithelial ovarian cancer. A multivariate classification model was developed that incorporated plasma concentrations of CA125, C-reactive protein (CRP), serum amyloid-A (SAA), interleukin-6 (IL6) and interleukin-8 (IL8) that were measured using in vitro diagnostics assays on medical device approved clinical analysers. The posterior probability values derived from the implemented algorithm were used for comparisons of the diagnostic performance between the multianalyte panel and CA125 using multiple methods; area under the curve (AUC) of the receiver operating characteristics curve, integrated discrimination improvement (IDI) and net reclassification improvement (NRI).
Results: Each of the biomarkers displayed significantly elevated plasma concentrations in malignant ovarian cancer patients compared with either benign or control subjects. For the discrimination of borderline and malignant ovarian cancer from control and benign subjects, the multivariate classification model showed a significantly greater AUC than that for CA125 alone (88.4% versus 84.3%, respectively, p < 0.001). At a posterior probability threshold of 0.5, the IVDMIA delivered a specificity of 92.3% and a sensitivity of 76.4%. When set at a specificity of 95%, the multimarker diagnostic delivered a sensitivity of 69.5% compared with 62.5% for CA125. Enhanced diagnostic performance of the IVDMIA over the use of CA125 alone was confirmed statistically by alternative comparisons using IDI and NRI.
Conclusions: This study confirms in an independent sample set that a blood-based multianalyte assay has significant advantages over CA125 for distinguishing symptomatic women with borderline and malignant ovarian cancer from controls or those with benign disease.