Proteomic biomarkers apolipoprotein A1, truncated transthyretin and connective tissue activating protein III enhance the sensitivity of CA125 for detecting early stage epithelial ovarian cancer

Abstract

Objective: The low prevalence of ovarian cancer demands both high sensitivity (>75%) and specificity (99.6%) to achieve a positive predictive value of 10% for successful early detection. Utilizing a two stage strategy where serum marker(s) prompt the performance of transvaginal sonography (TVS) in a limited number (2%) of women could reduce the requisite specificity for serum markers to 98%. We have attempted to improve sensitivity by combining CA125 with proteomic markers.

Methods: Sera from 41 patients with early stage (I/II) and 51 with late stage (III/IV) epithelial ovarian cancer, 40 with benign disease and 99 healthy individuals, were analyzed to measure 7 proteins [Apolipoprotein A1 (Apo-A1), truncated transthyretin (TT), transferrin, hepcidin, ß-2-microglobulin (ß2M), Connective Tissue Activating Protein III (CTAPIII), and Inter-alpha-trypsin inhibitor heavy chain 4 (ITIH4)]. Statistical models were fit by logistic regression, followed by optimization of factors retained in the models determined by optimizing the Akaike Information Criterion. A validation set included 136 stage I ovarian cancers, 140 benign pelvic masses and 174 healthy controls.

Results: In a training set analysis, the 3 most effective biomarkers (Apo-A1, TT and CTAPIII) exhibited 54% sensitivity at 98% specificity, CA125 alone produced 68% sensitivity and the combination increased sensitivity to 88%. In a validation set, the marker panel plus CA125 produced a sensitivity of 84% at 98% specificity (P=0.015, McNemar's test).

Conclusion: Combining a panel of proteomic markers with CA125 could provide a first step in a sequential two-stage strategy with TVS for early detection of ovarian cancer.

Figure 1

Box plots for levels of seven proteomic biomarkers in sera from women with benign pelvic masses, healthy individuals and patients with early stage epithelial ovarian cancer. One-way analysis of variance indicates that levels of Apo-A1 (P<0.00001), TT (P<0.00001), CTAPIII (P<0.0001), transferrin (P=0.00015) and hepcidin (P=0.00172) are significantly lower in ovarian cancer patients than in controls. With Wilcoxon analysis, only Apo-A1, TT, CTAPIII and transferrin were significant (P<0.05).

Figure 2

Plots of the ROC curves for models trained on six subsets of the MD Anderson data. These six models did use CA125. The isolated black point is the performance of CA125 Alone. The p value was computed by applying the Wilcoxon-Mann-Whitney test to the AUC value (bootstrap empirical p-value = 0.038).