With an observed increase of distant-stage colorectal cancer (CRC) among young patients in recent years, researchers have been searching for the reasons behind rising numbers and ways to counteract them. Carcinoids, a subtype of slow-growing cancer, have been found to contribute to the steadily rising incidence rate of early-onset colorectal cancer, which is diagnosed before the age of 50. This has created a need to assess the shifts toward distant-stage adenocarcinoma and its impact on public health.

Why Are We Seeing This Increase?

A study recently published in Cancer Epidemiology, Biomarkers & Prevention sought to understand how the proportions of distant-stage disease changed over time. Several studies have identified a significant increase (49%) in the average annual percent change for distant stage colorectal cancer in the 20-34 years age group. However, many of these studies do not report histological subtypes of CRC. 

With carcinoids increasing in younger patients, it is important to look at adenocarcinoma (most common cancer of the colon and rectum) staging independently from carcinoids (neuroendocrine tumors). Therefore, these researchers focused specifically on adenocarcinomas. Yearly adenocarcinoma incidence rates from the 2000-2016 Surveillance Epidemiology And End Results (SEER) data were stratified by stage, age, subsite, and race for 103,975 patients. Changes in the three-year annual incidence rate were calculated with the percent contribution of each cancer stage. Lastly, the subgroup with the highest proportion of distant-stage disease was determined.

The greatest percent increases were seen in distant-stage cancer when comparing data from 2000-2002 with 2014-2016. Here are a few significant findings of the study:

  • Colon-only distant adenocarcinoma increased most in 30-39-year-olds (49%)

  • Rectal-only distant-stage adenocarcinoma increased most in 20-29-year-olds (133%)

  • Based on race:

    • Distant stage proportions increased most for both colon- and rectal-only subsites in 20-29-year-old non-Hispanic Blacks (14% and 46%, respectively) 

    • The second most-impacted group was 20-29-year-old Hispanics with a 13% increase in the proportion of those affected by rectal-only, distant stage adenocarcinoma.

From these findings, we can conclude that the greatest burden of disease was on younger patients, highest in the non-Hispanic Black and Hispanic subgroups (despite relatively low absolute case counts). The researchers also uncovered that there is a decrease in early-stage disease in these early-onset groups. As we now know, younger patients are presented with higher risks, but the absolute incidence rates in the youngest subgroups remain relatively low.

These findings are important because they set a new precedent for patients under 50 who may not be aware that preventive screening for those at average risk of CRC starts at 45 years. Studies moving forward should also note that not all adenocarcinomas are categorized as early-onset CRC. Although this study is limited in its observational nature, it raises important questions in analyzing staging results, promoting screening opportunities, and keeping the general public aware of their risks. This study also presents potential solutions, including optimizing earlier screening and the risk-stratification of younger patients by family history and symptoms.

This post originally appeared June 1, 2022, on the Colon Cancer Foundation website. It is republished with permission