Performance of a Novel Blood-Based Early Colorectal Cancer Screening Assay in Remaining Serum after the Blood Biochemical Test

Background. Combination of multiple biomarkers was an effective strategy to improve sensitivity in cancer diagnosis and screening. However, the performance of the combination of methylated SEPT9 and SDC2 for detection of colorectal cancer (CRC) has yet to be reported. Methods. A new qPCR-based assay combining the detection of methylated SEPT9 and SDC2 was used. Methylation statuses of SEPT9 and SDC2 were examined in 19 sets of cancer tissues and paired adjacent tissues and further evaluated with 225 serum samples, including 111 CRC patients and 114 no evidence of disease individuals. Results. SEPT9 and SDC2 methylation levels were higher in 94.7% and 100.0% of cancer tissues than in their paired adjacent tissues. The sensitivities for detecting CRC by SEPT9 methylation alone and SDC2 methylation alone were 73.0% (95% CI: 63.6-80.8%) and 71.2% (95% CI: 61.8-79.2%), respectively, with the same specificity of 95.6% (95% CI: 89.6-98.4%). However, when SEPT9 methylation was combined with SDC2 methylation to detect CRC, the sensitivity was improved to 86.5% (95% CI: 78.4-92.0%) with a specificity of 92.1% (95% CI: 85.1-96.1%). Conclusion. The combination of methylated SEPT9 and SDC2 detection in serum has the potential to be a noninvasive strategy for CRC screening.