Patterns of colorectal cancer diagnosis among younger adults in a real-world, population-based cohort.

To review the patterns of early-onset (<50 years old) colorectal cancer (CRC) in Alberta across the past 15 years among different socioeconomic and demographic patient subgroups. This is a retrospective, population-based study based on Alberta administrative databases. Income level was identified via income information from the 2006 Canadian census. Patients with colorectal adenocarcinoma diagnosed 2004-2018 were included. Frequency analyses were used to examine the percentage of early-onset CRC cases among different subgroups over the period studied. Multivariable logistic regression analysis was used to examine factors associated with the development of early-onset CRC. A total of 24,912 patients were included, of whom 2096 (8.4%) were diagnosed at age <50 years and 22,816 (91.6%) at age ≥50 years. The percentage of patients diagnosed at age <50 years increased over time (10.2% in 2018 vs 7.9% in 2004; p < 0.003). Higher income was associated with younger age at diagnosis of CRC (odds ratio [OR] for quartile 1 vs quartile 4: 0.54; 95% CI: 0.47-0.62). Other factors associated with younger age at diagnosis included female sex (OR for male vs female: 0.85; 95% CI: 0.78-0.94), distal CRC (OR: 1.66; 95% CI: 1.50-1.84) and North zone (OR for South zone vs North zone: 0.74; 95% CI: 0.60-0.92). The proportion of patients (out of the overall CRC population) with early-onset CRC, increased in Alberta throughout the study duration (particularly left-sided CRC). There is a need to reassess the current age limits for CRC screening in Canada in view of these findings.