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Early-Onset Colorectal Cancer in Australia: Environmental, Microbial, and Policy Implications
Rathin Gosavi1,2,3,4, Stephen Bell5,6, Geraldine Ooi7
1Department of Colorectal Surgery, Cabrini Health, Melbourne, Victoria, Australia, rathin.gosavi@monash.edu.
Digestive Diseases (Basel, Switzerland)
|May 29, 2026
Summary
Early-onset colorectal cancer (EOCRC) is increasing, driven by factors beyond traditional risks. Gut microbiome changes and environmental exposures like microplastics and chemicals are implicated in accelerating EOCRC development.
Area of Science:
- Gastroenterology and Oncology
- Environmental Health
- Microbiology
Background:
- Early-onset colorectal cancer (EOCRC) incidence is rising in Australia, particularly in younger adults (<50 years).
- EOCRC exhibits distinct characteristics including a birth-cohort effect, left-sided and rectal tumor predominance, and advanced stage at diagnosis.
- The majority of EOCRC cases lack a family history, suggesting environmental and biological factors accelerate carcinogenesis in average-risk individuals.
Purpose of the Study:
- To synthesize current scientific understanding of EOCRC causes, focusing on microbial, dietary, and chemical exposures.
- To establish clinical, policy, and research priorities for addressing EOCRC in Australia.
Main Methods:
- Literature review of evidence on EOCRC aetiology.
- Analysis of contributing factors including traditional risks, hereditary syndromes, and environmental exposures.
- Synthesis of findings to inform clinical and policy recommendations.
Main Results:
- Traditional risk factors (obesity, metabolic syndrome, sedentary lifestyle, alcohol, smoking) contribute but do not fully explain EOCRC's rise or distal tumor prevalence.
- Hereditary syndromes are infrequent causes; tumor genetics resemble those of later-onset colorectal cancer.
- Gut dysbiosis, exposures damaging mucosal defenses, and DNA damage are implicated.
- Specific exposures like colibactin-producing E. coli, microplastics, plasticisers, PFAS, and cumulative antibiotic use are linked to EOCRC development through various mechanisms.
Conclusions:
- While traditional factors play a role, novel environmental exposures and gut microbiome alterations are key drivers of accelerating EOCRC.
- Disruptions to gut barrier function, chronic inflammation, and direct DNA damage are critical pathways.
- Further research and targeted interventions addressing these exposures are crucial for managing the EOCRC epidemic.
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