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Risk Factors in Sporadic Early-Onset Colorectal Cancer, Current Evidence and Emerging Insights: A Systematic Review
by
, and
Meghana Maddula
1,*,
Jordan E. Cohen
1,
Dulitha Kumarasinghe
2,
Mandy L. Ballinger
3,
Jaqueline L. E. Tearle
4,5,
Kylie R. James
4,5,
Adnan Nagrial
6,
Megan Barnet
1,5,7 and
Subotheni Thavaneswaran
1,5,7,8,* 1
Faculty of Medicine and Health, University of New South Wales, Sydney, NSW 2052, Australia
2
Department of Anaesthesia, Westmead Hospital, Sydney, NSW 2145, Australia
3
Centre for Molecular Oncology, University of New South Wales, Sydney, NSW 2052, Australia
4
School of Biomedical Sciences, University of New South Wales, Sydney, NSW 2052, Australia
5
Garvan Institute of Medical Research, Darlinghurst, Sydney, NSW 2010, Australia
6
Department of Medical Oncology, Westmead Hospital, Sydney, NSW 2145, Australia
7
The Kinghorn Centre, St Vincent’s Health Network Sydney, Sydney, NSW 2010, Australia
8
NHMRC Clinical Trials Centre, The University of Sydney, Sydney, NSW 2050, Australia
*
Authors to whom correspondence should be addressed.
Cancers 2026, 18(10), 1515; https://doi.org/10.3390/cancers18101515 (registering DOI)
Submission received: 13 April 2026
/
Revised: 1 May 2026
/
Accepted: 7 May 2026
/
Published: 8 May 2026
(This article belongs to the Section Systematic Review or Meta-Analysis in Cancer Research)
Simple Summary
Colorectal cancer is a major cause of cancer-related death worldwide and is increasingly being diagnosed in individuals under 50 years of age, when it is referred to as early-onset colorectal cancer. While a minority of cases are explained by recognised hereditary syndromes, most occur without an identified genetic cause and are considered sporadic. This suggests that some cases may be due to unrecognised or currently undefined hereditary syndromes, as well as environmental and lifestyle factors, and the interaction between them. In this systematic review, we synthesise current research to better understand potential risk factors and contributors. By identifying consistent patterns, our findings aim to improve understanding of the rising incidence of early-onset colorectal cancer and support the development of screening and prevention strategies and future research to identify underlying causes.
Abstract
Background: The incidence of early-onset colorectal cancer (EOCRC) is rising globally, yet its underlying risk factors remain incompletely understood, particularly in cases without recognised hereditary syndromes. Objectives: To update and synthesise the current body of evidence on modifiable and non-modifiable risk factors for sporadic early-onset colorectal cancer. Methods: A systematic review of peer-reviewed articles published in English reporting original observational research examining risk factors for sporadic early-onset colorectal cancer (<50 years old) was conducted. PubMed and EMBASE databases were searched from inception to March 2025. Across studies, effect measures varied; therefore, the synthesis focused on the consistency of associations rather than the direct comparison of effect sizes. Results: The initial search identified 2575 papers; 34 studies were included after screening. Several consistent associations were identified, with dietary and lifestyle factors along with metabolic conditions emerging as key risk factors. EOCRC risk was higher in males (adjusted odds ratio (aOR) 1.36–2.21 across studies), individuals of Caucasian ethnicity (aORs 1.48–2.56), and in individuals whose age was approaching 50 years (per year, aORs 1.05–1.11). Putatively sporadic EOCRC was associated with a family history of CRC or other cancers (aORs up to 8.61). Other key factors linked to higher risk included obesity (aORs 1.92–2.88; adjusted Hazard Ratios (aHRs) 1.04–1.82), metabolic syndrome (aORs 1.25–2.48; aHRs 1.2–1.26), diabetes (aORs 1.24–3.42), Western dietary patterns (aORs 1.84–2.99), and sedentary behaviours (adjusted relative risks (aRR) 1.69–2.44). Moderate-to-vigorous exercise appeared protective (aORs 0.34–0.58), as did higher vitamin D levels (aHRs 0.41–0.61). Evidence for smoking, alcohol, medications and early/in utero environmental exposures was inconsistent. Conclusions: Lifestyle and metabolic factors, including Western dietary patterns, obesity and sedentary behaviours, were associated with sporadic EOCRC. Family history also emerged as a significant contributor to putatively sporadic disease, suggesting heritable influences beyond recognised syndromes and interplay between environmental factors and genetic predisposition. Future research should focus on integrated tumour and germline profiling, including broader genomic analyses in well-characterised cohorts, to better understand potential pathogenic mechanisms and support the development of risk stratification approaches.
