Rising colorectal cancer risk in young adults calls for earlier screening, study suggests

By Tarun Sai LomteDec 7 2023Reviewed by Susha Cheriyedath, M.Sc.

In a recent study published in JAMA Network Open, researchers analyzed the prevalence of adenomas and advanced adenomas (AAs) and the incidence of colorectal cancer (CRC) among adults.

The incidence and mortality of CRC have reduced in various European countries and the United States (US) over the past three decades among people aged 55 and older. This reduction might have been due to greater adherence to screening. Meanwhile, CRC incidence and mortality rates in younger adults have increased.

Study: Colorectal Cancer and Precursor Lesion Prevalence in Adults Younger Than 50 Years Without Symptoms. Image Credit: mi_viri / Shutterstock

The American Cancer Society recommends reducing the age of people undergoing screening to 45 years. Colonoscopy is the standard for screening CRC. Adenomas elevate the risk of progression to CRC, and they are classified into non-advanced adenomas and AAs, and the AA-to-CRC transition rate increases with age. Additionally, male sex has been reported as an independent CRC-associated factor.

Males aged 45–49 had a comparable incidence of CRC and precursors as females 10 years older. Moreover, a study reported that CRC diagnosis was made at a more advanced stage among 40–45-year-old individuals than in 1990, suggesting increased CRC incidence and a shift in age at diagnosis. Notwithstanding, data on precursor prevalence among younger asymptomatic individuals are lacking.

About the study

In the present study, researchers examined the prevalence of AAs and adenomas among younger, symptom-free adults and the trends in CRC incidence in Austria. They analyzed over 305,000 screening colonoscopies within the quality assurance program from 2008 to 2018, mainly involving patients aged ≥ 50.

Nevertheless, a screening colonoscopy was also available for younger, asymptomatic adults in this program, and their main reason for undergoing a screening colonoscopy was the fear of cancer. Individuals with cancer symptoms, inflammatory bowel disease, or a family history of CRC were excluded.

Patients were stratified into five-year age groups, and the prevalence of AAs and adenomas was estimated. AAs were adenomas ≥ 10 mm with villus histology or high-grade dysplasia. The prevalence of serrated lesions (traditional serrated adenomas and sessile serrated lesions) was examined from 2012 to 2018. Besides, Statistics Austria provided CRC incidence data from 1988 to 2018.

Findings

The study included 296,170 patients who underwent screening colonoscopies during 2008–18. Of these, approximately 4% were aged under 50 years, and the remaining were aged ≥ 50. Complications were reported for 640 patients. The median detection rate was 21.4% and 6.6% for adenomas and AAs, respectively.

The incidence of CRC per 100,000 individuals increased from 9.1 to 10.2 incidents between 1988 and 2018 among males under 50 but decreased from 9.7 to 7.7 incidents in the same period for females aged < 50. For individuals aged 50 or older, it declined from 217 to 143 incidents between 1988 and 2018 among males and 168 to 97 incidents among females.

Overall, 21.4% of patients had at least one adenoma. Among males aged < 50, 1,166 had adenomas; among those aged ≥ 50, 62,384 had adenomas. The prevalence of adenomas was 61 individuals in 2008 and 150 in 2018 among those under 50, 2,646 individuals in 2008, and 10,673 individuals in 2018 among those aged ≥ 50.

In total, 20,069 patients had AAs. Among adults aged < 50, 160 females and 229 males had AAs. Among individuals aged ≥ 50, AAs were detected in 7,768 females and 12,042 males. The prevalence of AAs increased from 20 individuals in 2008 to 55 in 2018 among those aged < 50 and from 888 individuals in 2008 to 2578 in 2018 among those aged 50 or above.

In total, 5,410 individuals had serrated lesions, including 5,245 among those aged 50 or older and 165 among those under 50. The prevalence of serrated lesions increased from 10 patients in 2012 to 26 in 2018 among individuals under 50. Likewise, it increased from 232 to 1289 patients during the same period.

Conclusions

Taken together, the prevalence of adenomas increased among younger people since 2008, and this trend was evident in all age groups. The prevalence of AAs increased among younger adults but decreased among those aged 50 or older between 2008 and 2018. Since 1988, CRC incidence has declined among people aged ≥ 50 and increased in males younger than 50 but not in females. The findings suggest that screening should start at the age of 40 for males and 50 or later for females.