Retrospective cohort study of cancer mortality before age 50 years in Canada

Recent studies suggest that breast and lung cancer deaths are decreasing but colorectal cancer deaths have been increasing among people younger than 50 years in the US. A retrospective cohort study examined changes in cancer mortality for the 10 leading causes of cancer mortality since 2000 among people younger than 50 years in Canada. A total of 85 439 cancer deaths were identified among Canadians aged 20 to 49 years from 2000 to 2024. The 10 leading cancer sites contributed 59 858 cancer deaths in this population (70%). Decreasing or stable trends were observed for 9 cancer sites, with the largest decrease for lung cancer (average annual percent change[APC] -6.2%; 95% CI -6.8 to -5.5). In contrast, colorectal cancer showed an increasing trend (APC 1.1%; 95% CI 0.7-1.5). The number of colorectal cancer death among individuals aged 20 to 49 years increased from 300 in 2000 to 442 in 2024. The authors conclude that the decrease in lung cancer deaths was largely associated with effective public health campaigns against smoking, while the decrease in breast cancer deaths was largely associated with increased screening access, earlier detection, and better personalized treatment. The increase in colorectal cancer deaths suggests a possible generational change in etiology, such as higher prevalence of obesity and metabolic syndrome or increased exposure to unhealthy lifestyles and toxins.