Number of Older Biological Siblings and Early-Onset Colorectal Cancer Risk.

Colorectal cancer (CRC) is the third most common cancer in the United States.1 Although CRC incidence has declined in individuals >50 years, incidence is rising in adults <50 years (early onset).1 By 2027, CRC is projected to become the leading cause of cancer mortality in US adults <50 years.2 To combat the rising incidence of early onset CRC (EOCRC), national guidelines recently lowered the screening age from 50 to 45 years for average-risk individuals.3 Understanding the risk profile of EOCRC can help combat the rising burden in young adults, especially in those ineligible for screening.