People who develop precancerous colon polyps have significant differences in the type and diversity of bacteria in their gut flora compared to healthy people, a new study published in the US has found. UEG Week 2023European Union Annual Conference of Gastroenterology.
These changes can be detected before polyps turn into colorectal cancer, the first author says. Dr. Ranko Gaseza, researcher and professor at the University Medical Center in Groningen, the Netherlands. “If confirmed, these findings would indicate that examining the gut microbiome could improve current non-invasive fecal tests used to detect and prevent colorectal polyps and cancer. I mean,” he says.
How does this study build on previous research?
Previous research has found that certain strains of bacteria and the compounds they make in the gut are associated with a higher or lower risk of colorectal cancer. American Cancer Institute. However, it is not fully understood which comes first: whether microbiome changes change the course of cancer, or whether microbiome changes occur as a result of cancer.
Lower intestinal diversity associated with precancerous polyps
To investigate the association between different bacteria found in the gut and precancerous colon polyps, researchers compared data from more than 8,000 participants in the Dutch Microbiome Project with a national pathology database in the Netherlands. We linked and identified all cases of colon biopsy recorded over the past 50 years.
Researchers studied people who developed precancerous colorectal lesions before fecal collection between 2000 and 2015 (214 people) and those who developed lesions after fecal collection between 2015 and 2022 (214 people). The gut microbiome of 305 people was analyzed. They then compared their gut microbiome findings to those of people with normal colonoscopy findings (202 people) and the general population.
Researchers found that people with precancerous lesions had a reduced diversity of gut bacteria compared to healthy people.
It’s still unclear why certain people have “bad” microbes in their guts
These findings make sense, given that higher microbiome diversity is generally considered to be indicative of “good” gut health, while lower diversity is considered an unfavorable indicator. Dr. Gaseska says it’s true. “This means that patients with certain diseases, such as inflammatory bowel disease, [IBD] “The diversity of the microbiome in the gut has decreased,” he says.
Colorectal polyps usually take 5 to 10 years to develop
The study’s large number of subjects and long-term follow-up (researchers were able to follow participants for decades) were both key strengths of the study, he said. Dr. Sunil Kamatha hematologist and medical oncologist and assistant professor at the Cleveland Clinic in Ohio, was not involved in the study.
“In colorectal cancer research, it is especially important to follow participants over a relatively long period of time, as the progression from normal colon to polyp formation to cancer formation can take five to 10 years. “It requires a lot of observation, a lot of follow-up period,” he says.
Bacterial species associated with potential risk of colorectal cancer
“From previous studies, we know that some of the species we have identified are associated with the development of potentially genotoxic colorectal lesions,” Professor Gaseska says. This means that these species cause mutations in cells that can lead to cancer. “for example, Bacteroides fragilis “It is known to produce toxins that can contribute to chronic low-grade inflammation, and chronic enteritis is likely to be genotoxic/carcinogenic,” he added.
“Another example is Ackermencia “These species can degrade intestinal mucus and reduce the organism’s ability to defend against pathogens, again leading to chronic inflammation and potentially cancer,” he says.
Furthermore, the analysis revealed that bacterial species in this family Lachnospiracea and genus rosebria and eubacteria was associated with future lesion progression.
But researchers still don’t know why certain people have these “bad” microbes in their guts, Gaseska said. “And there is no clear consensus on the effectiveness of microbiome-altering treatments,” he added.
Can probiotics and prebiotics help prevent colorectal cancer?
If confirmed, these findings could help point the way to microbiome-targeted therapies such as fecal microbiome transplants and probiotics and prebiotics. “Large-scale testing will be needed to prove that such probiotics have the expected effects,” Gaseska says.
Work to develop these treatments is ongoing, and progress will likely be made in the near to medium term.
“The current difficulty in this field is that which bacteria end up being important or not important can vary widely from study to study. One in particular: Fusobacterium nucleatum, This is a bacteria that lives in the mouth and is associated with an increased risk of various cancers, including colorectal cancer. I was a little surprised that this study didn’t specifically point to that,” says Dr. Kamath.
Papers on the growing evidence of a link between Fusobacterium nucleatum The risk of colorectal cancer is Published in the November 2022 issue Frontiers of Cellular and Infectious Microbiology.
The discovery that rosebria The association with the development of precancerous polyps was also surprising, Kamath said. “It’s often associated with positive things because it’s been shown to help control blood sugar and help with weight loss,” he says.
These conflicting findings highlight that much of the research on the microbiome and its role in cancer is relatively new. This is a rapidly growing field, Kamath said. “More research is needed to really prove what’s really going on here,” he added.
Colorectal cancer is the third most common cancer
According to , colorectal cancer is the third most common cancer in both men and women in the United States, excluding skin cancer. American Cancer Society. It is estimated that there will be more than 150,000 new cases of colon and rectal cancer in the United States this year.
For people at average risk, regular screening with stool-based tests or visual tests such as colonoscopies or virtual colonoscopies is recommended starting at age 45.
Risk factors for colorectal cancer include age, medical history, genetic vulnerability, and lifestyle-related factors such as being overweight or obese, lack of physical activity, a diet high in processed and red meat, smoking, and heavy alcohol consumption. Contains factors. by society.
Should I look for probiotics to prevent colorectal cancer?
At this time, there is not enough solid evidence to recommend specific probiotics to reduce the risk of colorectal cancer, Kamath says.
He suggests focusing on known risk factors, such as achieving and maintaining a healthy weight. “In the United States, a lack of microbial diversity and poor gut health are driven by overweight and obesity. As data on concerns about colorectal cancer continues to grow, colorectal cancer is becoming the most concerning. “It’s becoming a risk factor for people with disabilities,” he says.
He recommends a Mediterranean diet for patients who want to reduce their risk. “I’m a big fan of that way of eating, focusing on lean meats, fatty fish, beans, legumes, nuts, fresh fruit, green leafy vegetables, and limiting processed foods,” he says.