Epidemiological Classification Changes and Incidence of Early-Onset Colorectal Cancer

Area of Science:

• Oncology
• Cancer Epidemiology
• Gastroenterology

Background:

• Previous studies indicated rising early-onset colorectal cancer (EOCRC) rates coinciding with changes in cancer registration guidelines.
• These studies did not simultaneously compare colorectal adenocarcinoma (ADC) and neuroendocrine neoplasms (NENs) patterns by age and stage.

Purpose of the Study:

• To analyze colorectal cancer incidence patterns by histopathological type and tumor stage at diagnosis.
• To compare these patterns in individuals younger than 50 years versus older patients.

Main Methods:

• A cohort study utilized data from the French Network of Cancer Registries (FRANCIM) from 2004 to 2021.
• Included individuals newly diagnosed with invasive colorectal cancer across 7 French administrative areas.
• Age-specific incidence rates of ADC and NENs were calculated and modeled using Poisson and Joinpoint regression.

Main Results:

• EOCRC incidence increased in individuals aged 15-39 years (females: 2.9% annually; males: 2.6% annually).
• Rates of ADC remained stable, while NEN rates increased, particularly from 2004-2013, before disappearing.
• The increase in NENs was most pronounced in the 15-39 age group (29.7% of EOCRC cases).
• Colorectal adenocarcinoma with distant metastasis (ADC M1) incidence rose across all ages.

Conclusions:

• The 2013 NEN classification change played a significant role in observed EOCRC incidence patterns, creating an artifactual rise.
• Public health officials should account for this classification artifact when interpreting EOCRC trends.