2023-05-26 01:27:13
Colon and rectal cancer is the most diagnosed malignant tumor in Spain, with more than 40,000 new cases each year. And the second that causes the most deaths, behind lung cancer. The age group that accumulates the most cases is the one that goes from 50 to 69 years, to which the campaigns of fecal occult blood screening, but oncologists are witnessing with concern an increase in diagnoses in younger people. In addition, these cases are usually diagnosed in advanced stages due to low clinical suspicion.
Recent studies from large European registries indicate that colorectal cancer rates have increased significantly in patients of 20 to 49 years during the last 25 years, mainly due to an increase in cancer of the distal colon and rectum. Similar trends are observed in the United States, Australia, and countries in Asia.
The reason for this increase is not exactly known, but now researchers at Georgetown University’s Lombardi Comprehensive Cancer Center have studied the microbiome of people with colorectal cancer and have discovered that the composition of bacteria, fungi and viruses in a person’s tumor varied significantly depending on whether they had been diagnosed with a disease of early onset (45 years or less) or late-onset (65 years or older). These results may help solve the puzzle of why more young people are developing colorectal cancer, particularly those who have no identifiable risk factors acquaintances.
Findings from this study will be presented at the 2023 American Society of Clinical Oncology annual meeting, in Chicago, in June.
Colorectal cancer incidence rates have been declining for several decades in people older than 55 years, in part due to the increased use of screening for early detection, particularly colonoscopy, which can find and remove polyps before they become cancerous. But nearly twice as many young adults under the age of 55 are being diagnosed with colorectal cancer compared to a decade ago, with the incidence rate rising from 11% in 1995 to 20% in 2020.
“Younger people with colorectal cancer have more biologically aggressive cancers and any survival benefits of being younger are outweighed by that more aggressive tumor biology. We also know that, for the most part, genetics does not explain the recent rise in early-onset disease. 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, so we believe that the microbiome may be an important factor in the development of the disease, as it it is involved in the interaction between genetics, the environment, diet and a person’s immune system,” said Benjamin Adam Weinberg, an associate professor of medicine at Georgetown Lombardi.
Scientists have long known that certain microbes can affect the lining of the colon and promote inflammation of the tissue. This can lead to mutations in the DNA of colon cells and lead to cancer. Researchers also know that one type of bacteria, Fusobacterium nucleatum (F. nuc), is able to promote cancerous growth by suppressing immune responses in the colon.
To better understand the role of the microbiome and how its influence varies by age of onset of colorectal cancer, Weinberg and colleagues looked at the DNA and microbiome of tumors from 36 colorectal cancer patients who were diagnosed before age 45 as well as samples. of 27 people who were diagnosed after age 65.
The researchers detected 917 unique species of bacteria and fungi in tumors. One of the most common bacteria found was F. nuc, which appeared equally in about 30% of both early and late-onset tumors. Differences were observed in Cladosporium sp.which was found more frequently in the disease of early startwhile Pseudomonas luteola, Ralstonia sp. y Moraxella osloensis were seen more frequently in the disease of late start.
In terms of 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 in people with early-onset disease.
Weinberg says they will continue to explore the relationship between the microbiome and other factors that contribute to 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. We are also interested in the circulating microbiome, such as bacteria that might be detected in a blood sampleand how this correlates with the bacteria in the gut and in the tumor,” concludes Weinberg.
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