Increasing Colorectal Cancer Incidence Before and After Age 50: Implications for Screening Initiation and Promotion of "On-Time" Screening.

Background: Early onset colorectal cancer (CRC) incidence is rising under age 50, with a birth cohort effect for increasing incidence among individuals born 1950 and later. It is unclear whether increasing incidence trends will confer increased risk beyond age 50, the previously most commonly recommended age to initiate screening, when screening availability might modify incidence trends.

Aim: Evaluate US trends in colorectal cancer (CRC) for ages 40-59 years.

Methods: We analyzed counts and incidence rates for CRC, including by anatomic subsite, using the US Cancer Statistics dataset covering 100% of the population 2003-2017. Joinpoint regression was used to quantify Average Annual Percent Change (AAPC) in cancer incidence by age subgroup.

Results: 470,458 CRC cases were observed age 40-59, with absolute numbers of rectal (n = 4173) and distal cases (n = 3327) per year for age 50-54 approaching age 55-59 cases for rectal (n = 4566) and distal (n = 3682) cancer by 2017. Increasing early onset rectal cancer incidence per 100,000 occuring under age 50 was observed to extend to age 50-54, from 4.9 to 6.3 for age 40-44 (AAPC 2.1; 95% CI 1.5-2.7), 9.3 to 12.0 for age 45-49 (AAPC 1.5; 95% CI 1.1-1.4), and from 16.7 to 19.5 for age 50-54 (AAPC 1.0; 95% CI 0.7-1.3).

Conclusions: CRC trends suggest observed increased risks under age 50 are also present after age 50, despite prior availability of screening for this group. Recent CRC trends support initiation of screening earlier than age 50, and promotion of "on-time" screening initiation.