Increasing Incidence Rates of Colorectal Cancer Among Younger Individuals in Canada

Researchers examined time trends in CRC incidence rates by area-level average household income among different age groups from 1992 to 2016.

Targeted interventions and further research are needed to address the increasing incidence rates of colorectal cancer (CRC) among younger individuals in Canada, particularly those in lower income quintiles, according to a population-based, retrospective cohort study published in JAMA Network Open.

CRC incidence rates among individuals aged less than 50 years have been increasing in many countries. Whether these changes are uniform across income and age groups remains unknown. Therefore, researchers in Canada examined time trends in CRC incidence rates by area-level average household income among different age groups from 1992 to 2016.

Individuals aged 20 years or older who had been previously diagnosed with CRC in Canada from 1992 to 2016 were included in the analysis, with data being sourced from the Canadian Cancer Registry. Average household income was determined by linking participants’ postal codes with data from the Canadian Census. Income levels were grouped by quintiles (Q), with Q1 representing those in the lowest income group and Q5 representing those in the highest.

Investigators found that there were 340,790 cases of CRC diagnosed from 1992 to 2016, with 11,790 cases (3.5%) being diagnosed in individuals aged 20 to 44 years. CRC incidence was highest in Q1 and lowest in Q5. This trend was stable across all periods.

The ratio between the maximum and minimum CRC incidence rates was found to be highest among the 20 to 29-year age group from 1992 to 1996 and 2012 to 2016. For individuals aged 45 to 49 years, CRC incidence rates increased only for those in the lower income quintiles, with higher incidence rates in the high-income quintiles.

CRC incidence rates were stable for all income quintiles in those aged 50 to 54 years, with less variability between income quintiles. For individuals aged 55 to 74 years, CRC incidence rates were stable or decreased for all income quintiles, and there was less variability in the rates by income quintile, particularly from 2012 to 2016.

After age 75 years, CRC incidence rates were stable or decreased, were highest for the lower income quintiles, and variability between income quintiles increased relative to younger age groups.

Study authors acknowledged their results were limited due to the lack of data on individuals in Quebec. Additionally, they did not analyze CRC incidence across different age groups by sex.  

The authors noted that, “Although a small percentage of the total number of CRC cases in Canada occurs among individuals aged 20 to 29 and 30 to 39 years, the increasing incidence rates and high variability between income quintiles are concerning.” “This issue must be addressed since younger adults with cancer already face significant challenges, including delays in diagnosis, because cancer is uncommon and awareness and suspicion of cancer are low in this population,” they concluded.

Disclosure: Some study authors declared affiliations with biotech, pharmaceutical, and/or device companies. Please see the original reference for a full list of authors’ disclosures. 

Reference

Decker KM, Lambert P, Bravo J, Demers A, Singh H. Time trends in colorectal cancer incidence rates by income and age at diagnosis in Canada from 1992 to 2016. JAMA Netw Open. 2021;4(7):e2117556. doi: 10.1001/jamanetworkopen.2021.17556