Background: Although colorectal cancer (CRC) predominantly affects older adults, a growing body of evidence indicates increasing incidence among younger populations worldwide. Early-onset colorectal cancer (EOCRC), defined as diagnosis before the age of 50, is associated with more aggressive tumor biology, delayed diagnosis, and poorer outcomes. In Brazil, population-based data on EOCRC trends remain scarce, particularly at the city level, limiting evidence-informed prevention and policy responses.
Objectives: To analyze age-standardized incidence rates and temporal trends of early-onset colorectal cancer in Goiânia, Brazil, over a 20-year period (2000–2020), stratified by sex and age group.
Methods: An ecological time-series study was conducted using incident EOCRC cases (<50 years) recorded in the Goiânia Population-Based Cancer Registry between 2000 and 2020. All newly diagnosed malignant tumors of the colon and rectum (ICD-10 C18–C20) among individuals aged 15–49 years were included. Incidence rates were calculated per 100,000 inhabitants using annual population estimates from the Brazilian Institute of Geography and Statistics. Age-standardized incidence rates were estimated by the direct method, adopting the WHO standard population (2000–2025). Trends were assessed using segmented regression (Joinpoint Regression Program v5.0), estimating the Average Annual Percent Change (AAPC) with 95% confidence intervals, adopting a 5% significance level. 
Results: A total of 1,152 EOCRC cases were identified during the study period, with a higher proportion among women (54.5%) than men (45.5%). The mean age at diagnosis was 39 years (SD: 6.7). Overall incidence rates ranged from 2.9 to 9.0 per 100,000 inhabitants between 2000 and 2020, showing a significant upward trend in both sexes. The AAPC was 2.8% (95% CI: 0.7–4.97) among men and 3.2% (95% CI: 1.1–5.3) among women. Age-stratified analyses revealed stable trends in individuals aged 15–29 years and non-significant increases in those aged 30–39 years. The most pronounced and statistically significant increase occurred in the 40–49 age group, with an AAPC of 3.9% (95% CI: 2.0–5.7). For the total population aged 15–49 years, incidence increased from 10.0 to 16.4 per 100,000, with a significant AAPC of 3.0% (95% CI: 1.4–4.6).
Conclusions: The incidence of early-onset colorectal cancer in Goiânia increased significantly over the last two decades, particularly among individuals aged 40–49 years. These findings reinforce EOCRC as an emerging public health issue and highlight the need to reassess prevention strategies, risk factor surveillance, and potential adaptations in screening policies for younger populations. Strengthening population-based cancer registries and integrating lifestyle and genetic risk assessments are critical to inform evidence-based cancer control strategies in Brazil.

Trends in Age-Standardized Incidence Rates of Early-Onset Colorectal Cancer (<50 years) by Sex and Age Group, Goiânia, Brazil, 2000–2020