Comparison of Tissue-Based Molecular Markers in Younger versus Older Patients with Colorectal Neoplasia.

Background: Emerging colorectal cancer (CRC) trends demonstrate increased incidence and mortality in younger populations, prompting consideration of average-risk CRC screening initiation at age 45 versus 50 years. However, screening test performance characteristics in adults 45-49 years have been minimally described. To inform the biologic rationale for multi-target stool DNA (mt-sDNA) screening in younger patients, we analyzed and compared tissue levels of methylation (BMP3, NDRG4) and mutation (KRAS) markers included in the FDA-approved, mt-sDNA assay (Cologuard®; Exact Sciences Corporation, Madison, WI). Methods: Within 40-44, 45-49, and 50-64 year age groups, archived colorectal tissue specimens were identified for 211 sporadic CRC cases, 123 advanced precancerous lesions (APLs; adenomas > 1 cm, high-grade dysplasia, > 25% villous morphology, or sessile serrated polyp; 45-49 and 50-64 age groups only), and 204 histologically normal controls. Following DNA extraction, KRAS, BMP3, and NDRG4 were quantified using QuARTS assays, relative to ACTB (reference gene). Results: None of the molecular marker concentrations were significantly associated with age (p > 0.05 for all comparisons), with the exception of NDRG4 concentration in APL samples (higher in older vs. younger cases; p = 0.008). However, NDRG4 levels were also statistically higher in APL case versus normal control samples in both the 45-49 (p <0.0001) and 50-64 (p <0.0001) year age groups. Conclusions: Overall, these findings support the potential for earlier onset of average-risk CRC screening with the mt-sDNA assay. Impact: These novel data address an identified knowledge gap and strengthen the biologic basis for earlier-onset, average-risk screening with the mt-sDNA assay.