Abstract
BACKGROUND: An increase in early-onset colorectal cancer has been observed globally, despite a decline in colorectal cancer incidence rates in many Western countries. Screening strategies for younger individuals are particularly challenging, as there are limited data on polyps in young individuals to guide clinicians. This study aimed to systematically review the current evidence surrounding polyp distribution in different age groups. METHODS: A literature search was performed in PubMed, Scopus, MEDLINE, Embase (OVID), Web of Science, and Cochrane Review databases using the keywords 'age' and 'polyp', and Medical Subject Heading terms 'age of onset', 'age factors', 'age distribution', and 'age groups', with no restrictions on publication year. Articles published in English that described the distribution of polyps (adenomatous, advanced adenomatous polyps, and sessile serrated lesions) or individuals with polyps according to different age groups were considered for inclusion. Younger patients were defined as those aged < 50 years. The outcomes of interest were the number of patients with polyps in the left and/or right colon, or the number of polyps per side of the colorectum in different age groups. RESULTS: From 12 470 articles, 24 met the eligibility criteria for the systematic review, and 12 were suitable for meta-analysis. Among younger people, 46.5% had right-sided and 75.9% had left-sided polyps. In comparison, 70.8% of the older group had right-sided and 61.9% had left-sided polyps. Meta-analyses of studies showed a greater proportion of younger people than older people with at least one left-sided polyp (mean difference 0.06, 95% confidence interval (c.i.) 0.03 to 0.09; P < 0.001). There was also a greater proportion of left-sided polyps in younger people (odds ratio 0.77, 95% c.i. 0.59 to 1.01; P < 0.001). CONCLUSION: Patients aged < 50 years have a greater tendency towards having polyps in the left colon, compared with people ≥ 50 years of age, similar to the distribution of early-onset colorectal cancer. This has implications for the methodology of screening and investigation of symptoms in those aged < 50 years.