Colorectal cancer is one of the most common cancers in the United Kingdom and the second biggest cause of cancer deaths.
Scientists from the University of East Anglia looked at DNA data from more than 9,000 patients. They discovered that only tumors in the colon and rectum have a special mix of microbes that can be recognized.
How the study was done
The researchers used whole‑genome sequencing data from over 11,000 cancer samples that covered 22 different cancer types.
When a tumor’s DNA is sequenced, tiny pieces of DNA from bacteria, viruses and other microbes are also captured. The team built computer tools to filter out the human DNA and keep the microbial bits.
They then compared the microbial data with the patients’ medical records.
A unique microbial pattern for colorectal tumors
The analysis showed that colorectal tumors consistently contained a specific community of microbes. This pattern was strong enough to tell these tumors apart from all other cancers.
In other cancers, such as lung or breast, no clear microbial fingerprint was found.
Potential clinical benefits
The microbial signature could help doctors confirm a colorectal cancer diagnosis more quickly.
Some microbes were linked to how patients did after treatment. For example, certain bacteria were tied to lower survival rates in sarcoma patients, while other microbes were connected to better outcomes.
These clues might one day allow doctors to predict which treatments will work best for each patient.
Whole‑genome sequencing as a tool
Experts say that as genome sequencing becomes routine in hospitals, checking the microbial DNA in tumor samples could be a cheap way to add useful information.
In oral cancers, the study also found that viruses like HPV could be spotted more reliably than with some current tests.
Collaboration and support
The project involved many universities and research institutes across the UK, Europe and the United States. Funding came from the Big C Cancer Charity and Prostate Cancer UK.