Circulating Tumor DNA in Addition to Fecal Immunochemical Test in a Dual-Test Colorectal Cancer Screening Approach

Early detection is paramount when reducing incidence and mortality of colorectal cancer (CRC). Current population-based screening programs primarily use fecal immunochemical test (FIT) to allocate individuals for colonoscopy although low specificity challenges colonoscopy capacities. We aimed to assess the potential of circulating tumor (ct)DNA markers for early CRC detection in a dual-test CRC screening approach among FIT positive individuals.

Plasma samples from 774 FIT positive (≥100 ng Hemoglobin/mL) individuals from the Danish CRC screening program were analyzed for hypermethylated DNA in the genes Branched Chain Amino-acid Transaminase 1 (BCAT1), Ikaros-Family Zinc Finger transcription 1 (IKZF1), and Interferon Regulator Factor 4 (IRF4). Multivariate logistic regression models were generated adding the ctDNA markers and age to the FIT value. The dual-test approach was benchmarked to FIT at specific thresholds.

The dual-test approach improved CRC detection compared to the FIT alone (AUC of 87.2 [95% CI, 82.9-91.4] vs AUC of 72.5 [95% CI, 67.0-77.9]). This was also seen when adding advanced adenomas to the outcome resulting in AUCs of 71.8 [95% CI, 67.8-75.8] for the dual-test approach compared to 65.5 [95% CI, 61.3-69.7] for the FIT model alone. Benchmarking the dual-test approach at FIT cut-offs between 100 and 600 ng Hb/mL showed a potential for either reducing the colonoscopy requirement by up to 56% or increasing CRC detection by up to 28%.

As increasing FIT cutoff will decrease CRC detection rate, application of the ctDNA panel can increase the sensitivity and specificity in a dual-test approach among asymptomatic individuals.