BACKGROUND: Currently, there are no FDA approved screening tools for detecting 
early stage ovarian cancer in the general population. Development of a 
biomarker-based assay for early detection would significantly improve the 
survival of ovarian cancer patients.
METHODS: We used a multiplex approach to identify protein biomarkers for 
detecting early stage ovarian cancer. This new technology (Proseek® Multiplex 
Oncology Plates) can simultaneously measure the expression of 92 proteins in 
serum based on a proximity extension assay. We analyzed serum samples from 81 
women representing healthy, benign pathology, early, and advanced stage serous 
ovarian cancer patients.
RESULTS: Principle component analysis and unsupervised hierarchical clustering 
separated patients into cancer versus non-cancer subgroups. Data from the 
Proseek® plate for CA125 levels exhibited a strong correlation with current 
clinical assays for CA125 (correlation coefficient of 0.89, 95% CI 0.83, 0.93). 
CA125 and HE4 were present at very low levels in healthy controls and benign 
cases, while higher levels were found in early stage cases, with highest levels 
found in the advanced stage cases. Overall, significant trends were observed for 
38 of the 92 proteins (p < 0.001), many of which are novel candidate serum 
biomarkers for ovarian cancer. The area under the ROC curve (AUC) for CA125 was 
0.98 and the AUC for HE4 was 0.85 when comparing early stage ovarian cancer 
versus healthy controls. In total, 23 proteins had an estimated AUC of 0.7 or 
greater. Using a naïve Bayes classifier that combined 12 proteins, we improved 
the sensitivity corresponding to 95% specificity from 93 to 95% when compared to 
CA125 alone. Although small, a 2% increase would have a significant effect on 
the number of women correctly identified when screening a large population.
CONCLUSIONS: These data demonstrate that the Proseek® technology can replicate 
the results established by conventional clinical assays for known biomarkers, 
identify new candidate biomarkers, and improve the sensitivity and specificity 
of CA125 alone. Additional studies using a larger cohort of patients will allow 
for validation of these biomarkers and lead to the development of a screening 
tool for detecting early stage ovarian cancer in the general population.