Increasing Incidence of Colorectal Cancer in Young Adults

Abstract

Background: Colorectal cancer (CRC) incidence and mortality has been declining in the U.S. Despite success in reducing CRC incidence, incidence of early-onset CRC has increased markedly. In this study, we identified age-related disparities in CRC incidence and mortality, and investigated differences in anatomical distribution of colon cancers between populations.

Methods: CRC trends were evaluated using Surveillance, Epidemiology, and End Results Program Data from 1980-2016 for individuals under age 50 and 50 years and older. Rates and ratios were calculated using SEER^∗Stat. Regression analyses were calculated using Joinpoint.

Results: Increased CRC incidence among individuals under age 50 was observed. Among individuals under age 50, incidence-based mortality (IBM) stabilized, while incidence and IBM decreased for individuals aged 50 years and older. Normalized trends indicated increased rectal cancer incidence for individuals under age 50, particularly among individuals aged 30-39. Similar incidence of proximal and distal colon cancers in individuals under age 50 was observed, while colon cancers in individuals aged 50 and older were primarily distal.

Conclusions: We found age-related disparities in CRC incidence and IBM between individuals under age 50 and age 50 years and older. Increasing incidence rates of rectal cancer substantially accounts for this disparity among individuals under age 50. The escalating trends of early-onset CRC warrant investigation into the factors leading to the population-level trends.

Figure 1

Colon and rectal cancer incidence and mortality rates stratified by age, 1980–2016. Age-adjusted incidence and incidence-based mortality (IBM) rates per 100,000 persons from 1980–2016 were derived from SEER9 program data. Colon and rectal cancer incidence and IBM trends of individuals under the age of 50 (a, c) and age 50 and older (b, d). Annual percentage change (APC) are quantifications of the changes in trends. Asterisks (^∗) designate statistical significance calculated in the permutation model.

Figure 2

Comparison of normalized incidence and mortality rates between age 20–49 and 50 and older by tumor subsite, 1980–2016.Rates of individuals age 20–49 and 50 and older from 1980–2016 from SEER9 were normalized to the 1980 rate to better visualize the magnitude of differences in incidence and IBM trends by age over time. Normalized rates were divided into 10-year age intervals: 20–29 (a), 30–39 (b), 40–49 (c), 50–59 (d), 60–69 (e), 70–74 (f), and 75+ (g).

Figure 3

Trends in colon tumor subsite-specific incidence and mortality rates among individuals age 20–49 and 50 and older, 1980–2016.Age-adjusted incidence and mortality rates per 100,000 from 1980–2016 were derived from SEER9 program data and subdivided into proximal and distal colon tumor subsites using ICD-O-3 codes, to examine rates over time. Proximal and distal colon cancer incidence and IBM rates are depicted for age 20–49 (a, c) and 50 and older (b, d). Asterisks (^∗) designate statistical significance calculated in the permutation model.

Figure 4

Trends in colon tumor subsite-specific incidence rates stratified by age, 2000–2016.Age-adjusted incidence rates per 100,000 persons from 2000–2016 were derived from SEER18 program data. Colon cancer incidence trends were calculated for individuals age 20–29 (a), 30–39 (b), and 40–49 (c). Annual percentage change (APC) are quantifications of the changes in trends. Asterisks (^∗) designate statistical significance calculated in the permutation model.