Early-onset colorectal cancer in patients younger than 50 years: a systematic review of the literature.

Early-onset colorectal cancer (EO-CRC) refers to CRC diagnosed before the age of 50. Its incidence has risen in recent years, turning researchers' attention to its oncologic behavior and potentially modifiable risk factors. In this review, PubMed/MEDLINE database was searched for all original research articles concerning EO-CRC. The inclusion criteria were CRC patients under 50, without a known predisposing factor for malignancy or an inherited CRC syndrome, presenting oncological characteristics and outcomes. All studies were assessed for bias, based on the ROBINS-E 2022 tool, and were synthesized in a qualitative analysis. Twenty-nine articles, reporting on 64,376 EO-CRC patients, were included in the qualitative synthesis. Results were classified into 3 categories: a) demographics; b) histopathologic characteristics; and c) treatment outcomes. Of these publications, 21 studies agreed that rectum (45%) and left-sided (47.1%) cancers are most common in younger patients, and 5 indicated that the highest prevalence of CRC concerns the 40-49 years age group. Seventeen of 29 studies reported a higher stage (III and IV) on diagnosis, with lymphovascular and perineural invasion. Our review has some limitations: as it was based on a single database, not all studies provided information on the variables; and patients were not categorized in all studies in the same age groups, although all were under 50 years. As EO-CRC is on the rise, the need for closer monitoring and possibly earlier screening becomes apparent. Further research should focus on finding novel screening biomarkers and modifiable risk factors that would decrease mortality and improve patient outcomes.