He Colorectal cancer It is among the most diagnosed cancers worldwide, after breast and lung cancers, and accounts for around 9.4% of cancer deaths in the world, according to data from the Spanish Society of Medical Oncology (SEOM). It especially affects those over 50 years of age – especially between 50 and 69 years of age – but for some time now the incidence of this neoplasia has been increasing in younger people.
The implementation of diagnostic tests such as colonoscopywhich can detect polyps to remove them before they become cancerous, has allowed colorectal cancer rates to drop, but nearly double people under 55 years than a decade ago, which means an increase in the incidence rate that goes from 11% in 1995 to 20% in 2020.
Now, new research from Georgetown University’s Lombardi Comprehensive Cancer Center could help explain this phenomenon. Specifically, researchers have studied the microbiome of people with colorectal cancer and have discovered that the composition of bacteria, fungi and viruses in the tumor of a patient varied significantly depending on whether the disease was diagnosed at a young age (45 years or less), or from the age of 65.
The findings will be presented at the American Society of Clinical Oncology 2023 annual meeting in Chicago in June and may help solve the puzzle of why more young people are developing colorectal cancerespecially in the case of those who do not have known risk factors for the disease.
“We have trillions of bacteria in our bodies, some of which are implicated in the development of colorectal cancer. Therefore, we believe that the microbiome may be an important factor in the development of the disease.”
“Younger people with colorectal cancer have more biologically aggressive cancers, and any survival benefit they have from being younger is outweighed by the more aggressive tumor biology. We also know that, for the most part, genetics does not explain the recent rise in early-onset disease,” said Benjamin Adam Weinberg, MD, MD, associate professor of medicine at Georgetown Lombardi. “But we have trillions of bacteria residing in our bodies, including in our gut, some of which are implicated in the development of colorectal cancer. Therefore, we believe that the microbiome may be an important factor in the development of the disease, since it is involved in the interaction between genetics, the environment, diet and a person’s immune system.”
Microorganisms that inflame the colon and promote cancer
Some microbes can alter the lining of the colon and promote its inflammation, which can trigger mutations in the DNA of colon cells and lead to cancer, scientists already know. Researchers also know that the bacteria Fusobacterium nucleatum (F. nucleatum)can promote cancerous growth by suppressing immune responses in the colon.
To better understand the role of the microbiome (a community of microorganisms and their genetic characteristics) and how its influence varies depending on how old a patient is when colorectal cancer develops, Weinberg and colleagues looked at the DNA and tumor microbiome of 36 patients. with colorectal cancer who were diagnosed before the age of 45, and samples from 27 people who were diagnosed after the age of 65.
The researchers detected 917 unique species of bacteria and fungi in the tumors. F. nucleatum it was one of the most common bacteria and was found in about 30% of early-onset and late-onset tumors alike. Differences were observed in Cladosporium sp., which was more frequently detected in early-onset disease, whereas Pseudomonas luteola, Ralstonia sp. y Moraxella osloensis they were seen more frequently in late-onset disease.
Regarding the composition, Clostridium perfringens, Escherichia coli, Leptotrichia hofstadii, Mycosphaerella sp., Neodevriesia modesta, Penicillium sp. and Leptosphaeria sp. each made up 11% of the microbiome in people with late-onset disease, but these organisms were not found at all in people with early-onset disease.
Weinberg has indicated that they intend to continue investigating the relationship between the microbiome and other factors that influence colorectal cancer. “Because we have tumor genetic data and diet questionnaire results from many of our patients, we hope to explore more relationships and other aspects of how the microbiome affects colorectal cancer progression in the future,” he said. “We are also interested in the circulating microbiomesuch as the bacteria that might be detected in a blood sample, and how this correlates with the bacteria in the gut and in the tumor.”