Diagnostic performance of LINE-1 repetitive elements in stool DNA for non-invasive detection of colorectal cancer.

BACKGROUND

The need for accurate, cost-effective, non-invasive screening tests for colorectal cancer (CRC) persists. Repetitive genomic elements like Long Interspersed Nuclear Element-1 (LINE-1), due to their high copy number and cancer-associated alterations, present a promising but unexplored target in stool DNA for CRC detection.

METHODS

In this cross-sectional study, stool DNA was extracted from 38 patients with histologically confirmed CRC and 39 healthy controls. The concentration of human DNA was quantified via quantitative PCR targeting two short LINE-1 amplicons (55-bp and 60-bp). Diagnostic performance was evaluated using ROC curve analysis to determine sensitivity, specificity, and predictive values.

RESULTS

The concentration of stool DNA, measured by LINE-1 qPCR cycle threshold (Ct) values, was significantly higher in CRC patients compared to controls (p < 0.001 for both amplicons). The 60-bp LINE-1 amplicon demonstrated superior diagnostic accuracy with an area under the ROC curve (AUC) of 0.92 (95%CI 0.85-0.98), compared to 0.83 (95%CI 0.73-0.93) for the 55-bp amplicon. At the optimal cut-off (Ct ≤ 24.19), the 60-bp marker achieved a sensitivity of 87.0%, specificity of 78.4%, a positive predictive value (PPV) of 71.4%, and a negative predictive value (NPV) of 90.6%. The 55-bp amplicon showed higher sensitivity (95.7%) but lower specificity (59.5%).

CONCLUSION

Quantitative analysis of LINE-1 repetitive elements in stool DNA, particularly using a 60-bp amplicon, demonstrates excellent diagnostic accuracy for detecting CRC. This single-marker, qPCR-based assay represents a simple and potentially low-cost non-invasive strategy, warranting further validation in large-scale screening populations and assessment of its efficacy for detecting precancerous lesions.