Changes in demographics and patterns of colon cancer in the United States: A comprehensive SEER analysis 2010–2021.

Abstract

3607 Background: Over the past two decades, colon cancer has remained a leading cause of cancer-related morbidity and mortality in the United States. Changes in population dynamics, environment, and lifestyle have contributed to shifts in age, gender, tumor site, and stage at diagnosis. However, the extent of these changes over time remains underexplored. Understanding these temporal changes is crucial for improving screening strategies, identifying at-risk populations, and optimizing resource allocation. Methods: We conducted a cohort study of initial colon cancer diagnoses using the National Cancer Institute, Surveillance Epidemiology and End Results Program (SEER) over the period 2010 through 2021. The SEER data is comprised of 22 different registries across the United States (US), which captures approximately 47.9% of the US population. The exposure was the year of diagnosis, and the outcomes were the distributions of age, sex, site, and stage at initial diagnosis. Temporal trends in proportions were measured using Spearman correlation (ρ). The differences between distributions in 2010 vs. 2021 were measured using Fisher’s test with the standardized mean difference (SMD) as effect size. 95% confidence intervals (95% CI) for proportions were determined using the normal approximation. Results: A total of 670,923 records were included in the study. The distribution of ages at initial diagnosis changed significantly over the study period (SMD = 0.1713, p-value < 0.0001). In 2010, the mode of age group distribution was ≥ 85 years, 12.1% (11.8%–12.4%). The proportion aged ≥ 85 trended down over the period (ρ = -0.9930, p value < 0.0001) from 12.1% (11.8%–12.4%) to 9.6% (9.3%–9.8%). In 2021 the mode of age group distribution at diagnosis was 65 to 69 years, 13.2% (12.9% - 13.5%). The proportion of males trended up over the period (ρ = +0.9021, p value < 0.0001), increasing from 51.8% (51.4% - 52.2%) to 53.2% (52.8% - 53.6%). The difference in cancer stage was significant (SMD = 0.1818, p value < 0.0001), with localized colon cancer decreasing (ρ = -0.9371, p value < 0.0001) from 38.9% (38.5% - 39.3%) to 33.8% (33.4% - 34.1%) and distant colon cancer increasing (ρ = +0.9301, p value < 0.0001) from 20.1% (19.8% - 20.5%) to 22.9% (22.5% - 23.2%). The difference in location was significant (SMD = 0.1185, p value < 0.0001), with rectum as location trending up (ρ = +0.9330, p value < 0.0001) from 21.7% (21.3% to 22.0%) to 24.6% (24.3% to 25.0%). Conclusions: The current findings suggest a significant shift in colon cancer presentation in the United States over the past decade. There is a significant increase in incidence among younger males, a trend towards more distant-stage cancers indicating delay in detection, and a growing prevalence of rectal cancers as the primary site. Changes in screening strategies and reinforcement of community awareness are necessary to improve the mortality rate.