Colon Age: A Metric for Whether and How to Screen Male Veterans for Early-Onset Colorectal Cancer.

We aimed to develop a metric for estimating risk for early-onset colorectal cancer (EOCRC) to help decide whether and how to screen persons < age 50. We used risk prediction models derived and validated on male Veterans to calculate the relative risks (RRs) for 6 scenarios: one low-risk scenario (no risk factors present), four intermediate risk scenarios (some factors present), and one high-risk scenario (all factors present) for three age groups (35-39, 40-44, and 45-49 years). For each scenario, we estimated absolute CRC risk using SEER CRC incidence rates and each scenario's RR. We identified the current SEER 5-year age group to which the revised estimate was closest and refer to the midpoint of this group as the "colon age". When the revised estimate was ≥ that for 50-54-year-olds and for 70-74-year-olds, respective recommendations were made for (any) CRC screening and screening with colonoscopy. Among the scenarios, there was inconsistency between the two models for the 35-39 and 40-44 age groups, with only the 15-variable model recommending screening for the higher-risk 35-to-39-year-olds. Both models recommended screening for some intermediate risk and high-risk 40-44-year-olds. The models were well-aligned on whether and how to screen most 45-49-year-olds. Using risk factors for EOCRC with CRC incidence rates, "colon age" may be useful for shared decision making about whether and how to screen male Veterans < 50 years. For 45-49-year-olds, the 7-variable model may be preferred by patients, providers, and health systems.