Williams Cancer Institute



Colorectal cancer, traditionally associated with individuals over 50, is increasingly affecting younger populations without the benefit of routine screening. A recent study, published in eBioMedicine, delves into the gut microbiome, specifically exploring microbial differences in colorectal cancer patients of varying age groups. This exploration could hold the key to early diagnosis methods.

Researchers examined the gut microbiome of 136 individuals under 50 (median age 43) and 140 individuals over 50 (median age 73) with colorectal cancer. The findings revealed distinct sets of bacteria present in tumors of younger and older patients, sparking potential implications for early detection strategies.

Colorectal cancer is not solely linked to genetics, with environmental factors playing a significant role. High-fat, low-fiber diets and alcohol consumption are associated with this cancer, while fiber-rich diets show a protective effect. The connection between dietary choices, gut bacteria, and cancer risk has long been hypothesized.

Tissue samples from cancer patients were retrospectively analyzed, extracting microbiome data directly from tumors and adjacent noncancerous tissue. Both age groups exhibited a reduction in bacterial species diversity within tumors compared to surrounding tissue, with a more pronounced decrease in the older group. This indicates that only specific gut bacteria can thrive in the low-oxygen, inflamed environment of a tumor.

However, the exact role of these bacteria within tumors remains unclear. Mechanistic studies are needed to understand their impact on tumor growth and behavior. The study identified certain bacterial species more prevalent in tumors of one age group over the other, suggesting a potential correlation between specific gut microbes and colorectal cancer.

The presence of Akkermansia, a group of bacteria more frequently found in the younger age group, was linked to smaller tumors. Probiotic treatment with live cultures of Akkermansia hindered tumor growth in a mouse study, sparking discussions about the potential role of probiotics in controlling colorectal cancers.

While the study presents correlations between certain gut microbes and colorectal cancer, it doesn’t establish causation. The complex interactions among microbial communities within tumors make it challenging to pinpoint the exact impact of individual species. Nonetheless, the findings open avenues for harnessing the microbiome for early cancer diagnosis.

Lead author Naseer Sangwan sees the potential for accurately predicting cancer occurrence in young people. Early diagnosis is typically challenging in individuals under 45, who haven’t undergone routine colonoscopies. Lowering the screening age might not be the most practical solution due to invasiveness and associated adverse effects. However, Sangwan envisions a future where detecting specific microbes in stool samples could streamline the identification of individuals needing closer scrutiny for colorectal cancer.

As the scientific community continues to unravel the intricate relationship between gut microbiota and colorectal cancer, these insights may pave the way for more targeted and less invasive methods of early cancer detection. The prospect of leveraging microbial clues holds promise for transforming colorectal cancer diagnosis and improving outcomes, especially in younger populations.

Reference: Barot, S. V., Sangwan, N., Nair, K. G., Schmit, S. L., Xiang, S., Kamath, S., Liska, D., & Khorana, A. A. February 01, 2024. Distinct intratumoral microbiome of young-onset and average-onset colorectal cancer. EBioMedicine, 100(104980), 104980. https://doi.org/10.1016/j.ebiom.2024.104980

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