Epidemiologic Trends in Colorectal Cancer: Age-Related Variations and Site-Specific Patterns Over Two Decades

Document Type

Conference Proceeding

Publication Date

6-1-2025

Publication Title

Journal of Clinical Oncology

Abstract

Background: Colorectal cancer (CRC) is the 2nd most common cause of cancer related death in the United States (1). While the incidence of CRC in the general US population is declining due to screening efforts (2), the rate among adolescent/younger adults continues to increase with up to a 2% annual increase in those less than 50 years old (1). One review suggests that CRC that occurs in patients aged < 45 may differ pathologically and genetically from CRC in adults ≥ 45 (3). We aimed to determine if there was a difference in the incidence and anatomic locations of CRC among different age groups. Methods: This is a retrospective cohort analysis using data from the Surveillance, Epidemiology, and End Results (SEER) database. We included all patients aged > 18 years, diagnosed with colorectal cancer from years 2000-2021. The following parameters were extracted and analyzed: Age, sex, race, anatomic site of the primary tumor, and presence of metastases at diagnosis. We summarized demographic and clinical characteristics using means, medians, and proportions. Subgroup analyses was performed for younger ( < 45 years) and older (≥ 45 years) patients, and by time periods (2000-2010 vs. 2011-2021). Fisher’s exact test was used for comparisons of categorical variables between groups. The Kruskal-Wallis rank sum test was used to compare continuous or ordinal variables across multiple groups. All statistical analyses were performed using R software (version 4.2.0). Results: A search of the SEER database revealed 800,400 diagnoses of CRC between 2000-2021. Subgroup A included patients age < 45 (N = 47,615/6%) and subgroup B included patients age ≥45 (N = 752,785/94%). Female patients made up 48.1% of all cases while male patients made up 51.9%. White patients composed 79.3% while Black and other races made up 20.8% of all cases. Gender and race distribution was similar among all subgroups. Frequency and proportion of metastasis to bone, brain, liver, lung and distant lymph nodes were also similar in all subgroups. 403,791(50.4%) colorectal cancers were diagnosed between 2000-2010 while 396,609 (49.6%) were diagnosed between 2011-2021. Although slightly less cancers were diagnosed overall between 2011-2021, in subgroup A, this period accounted for 57.3% of the diagnoses. The most common cancer site was the rectum/rectosigmoid junction (29.4%). However, it made up 37.4% of total cancers in young adults (subgroup A). Similarly, although the appendix only comprised 2.5% of total cancers, in subgroup A, it represented 12% of total colorectal cancers. Conclusions: We confirm that the number of young adults with CRC is increasing. Between 2011-2021, there were 7000 more cancers diagnosed in younger adults compared to the preceding 10-year period. Adults younger than 45 were 4.8X more likely to develop adenocarcinoma in the appendix compared to other large bowel sites. More research on the genetic factors that make appendiceal cancer distinct may offer insight into why CRC in younger patients is more aggressive.

Volume

43

Issue

16 Suppl

First Page

e15678

Comments

2025 ASCO (American Society of Clinical Oncology) Annual Meeting, May 30 - June 3, 2025, Chicago, IL

Last Page

e15678

DOI

10.1200/JCO.2025.43.16_suppl.e15678

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