Emerging cancer incidence trends in Canada: The growing burden of young adult cancers.

BACKGROUND: Recent studies have identified increases in cancer incidence among younger adults for some cancers. This study examined incidence trends for 28 cancers in Canada by age and birth cohort from 1983 to 2012. METHODS: Canadian incidence data for 20 to 84 year-olds were obtained from the Cancer Incidence in Five Continents Plus database. Age-period-cohort modeling was used to estimate the average annual percentage changes (AAPCs) and incidence rate ratios (IRRs) for 10-year birth cohorts (reference cohort, 1943) for 28 cancer types. RESULTS: Incidence increased for 13 cancer sites among adults younger than 50 years (1983-2012), with the largest increase occurring for rectal cancer (AAPC20-24 , 5.62; 95% confidence interval [CI], 3.77-7.51) and colon cancer (AAPC20-24 , 4.08; 95% CI, 2.89-5.29). Compared with the 1943 birth cohort, persons born circa 1988 had approximately 5- and 2-fold greater risks of rectal cancer (IRR, 4.98; 95% CI, 2.87-8.63) and colon cancer (IRR, 2.31; 95% CI, 1.62-3.30), respectively. Incidence decreased among younger adults for 9 sites (1983-2012), with the largest decreases observed for lung cancer (AAPC25-29 ,-2.29; 95% CI, -3.57 to -0.98), cervical cancer (AAPC25-29 , -1.29; 95% CI, -1.67 to -0.90), and melanoma (AAPC25-29 , -0.61; 95% CI, -0.97 to -0.24). Decreased risks in recent birth cohorts were observed for all sites with decreasing trends in younger adults. For example, the risk of lung cancer was 60% lower in the 1988 birth cohort than the 1943 birth cohort (IRR, 0.42; 95% CI, 0.23-0.78). CONCLUSIONS: Incidence among young adults is increasing for some cancers associated with obesity but decreasing for many cancers associated with infections or smoking. Although further studies are needed to replicate these findings and understand the etiology of early-onset cancers, measures to promote healthy behaviors in young adults warranted.

Trends in the Incidence of Cancer Among Adolescent and Young Adults in Alberta, 1983-2017: A Population-Based Study Using Cancer Registry Data.

Purpose: To describe the cancer incidence burden and trends among adolescent and young adults (AYAs) in Alberta, Canada over a 35-year period. Methods: We obtained data from the Alberta Cancer Registry on all first primary cancers, excluding non-melanoma skin cancer, diagnosed at ages 15-39 years among residents in Alberta from 1983 to 2017. Cancers were classified by using Barr's AYA cancer classification system. Age-standardized incidence rates (ASIR) and the average annual percentage change (AAPC) in incidence rates were calculated. Statistically significant changes in the AAPC during the study period were assessed using Joinpoint regression. Results: Overall, 23,652 incident cases of AYA cancer were diagnosed in Alberta. Females accounted for ∼60% of the diagnoses. AYA cancer increased significantly over the study period overall (AAPC: 0.5%; 95%CI: 0.3%-0.7%), for each sex (AAPCmale: 0.7%; 95%CI: 0.4%-0.9%; AAPCfemale: 0.4%; 95%CI: 0.2%-0.6%), and among male and female 20-39 year-olds. Although statistically significant increases were observed in 11 out of 29 cancer sites for at least a portion of the study period, with significant AAPCs ranging from 0.8% (95%CI: 0.01%-1.5%) to 6.6% (95%CI: 4.6%-8.5%), the main driver was thyroid cancer (AAPC: 3.7%; 95%CI: 3.2%-4.2%). Statistically significant decreases were observed for six cancer sites, with AAPCs ranging from -6.4% (95%CI: -8.7% to -4.1%) to -1.1% (95%CI: -1.8% to -0.5%). Conclusions: There is a growing cancer burden among AYAs in Alberta, which is driven primarily by thyroid cancer and early-onset cancers in males. These results highlight the need for etiological studies and tertiary strategies to prevent and mitigate morbidity and mortality in the AYA population.