Colorectal cancer risk linked to gut microbiome alterations | Harvard T.H. Chan School of Public Health

May 28, 2026 - 03:00

Even more than ten years after a precancerous growth called an adenoma is removed from the colon, the gut microbiome and its related metabolites may still show lasting changes that increase the risk of colorectal cancer, according to new research from the Harvard T.H. Chan School of Public Health.

The study suggests that the biological footprint of an adenoma does not simply vanish after surgical removal. Instead, the gut's microbial community and the chemical compounds it produces can remain altered for over a decade. This persistent imbalance, known as dysbiosis, may continue to drive inflammation and other processes that raise the likelihood of cancer developing later.

Researchers analyzed data from a large group of participants who had undergone colonoscopies. They compared the gut microbiomes of people who had a history of adenomas with those who had no such history. The differences were significant and long-lasting. The findings point to the possibility that screening for these microbial changes could help identify individuals who remain at high risk even after polyps are removed.

The study adds weight to the growing understanding that colorectal cancer is not just a genetic disease but is heavily influenced by the environment inside the gut. While removing adenomas is still a critical step in prevention, this work suggests that monitoring the microbiome could become an important part of long-term follow-up care. The researchers hope the results will lead to new strategies for reducing risk, possibly through dietary changes or targeted therapies that restore a healthier balance of gut bacteria.