Early-onset disease (at <50 years of age) accounts for 10% of colorectal cancer cases, and the incidence is increasing, particularly in high-income countries. Patients often present with advanced disease in the left colon. One in six patients has deficient DNA mismatch repair. Screening is now recommended to begin at 45 years of age.

https://www.nejm.org/doi/full/10.1056/NEJMra2200869