Last year, speakers at the annual meeting of the American Society of Clinical Oncology – the world’s leading cancer conference – issued a dire warning.
Cases of colorectal cancer were rising rapidly among the over-40s, they said, so much so that cases in this age group are expected to double by 2030, with the disease the main source of deaths in those aged 20 to 49 will be caused by cancer. year olds towards the end of the decade.
“Studies show this increase in early colorectal cancers,” said Dr Dimitra Lamprinaki, a researcher at the Quadram Institute in Norwich. “The problem is that some of these cases are asymptomatic, but younger people may also ignore signs of cancer that can progress and become difficult to remove.”
This is part of a general trend. Cancer rates under the age of 50 are rising rapidly worldwide, according to recent research, increasing by 79 percent between 1990 and 2019. But while lifestyle factors such as highly processed diets and heavy alcohol consumption in the millennial generation are likely to blame, scientists have discovered an important new connection has been discovered: microbes that these bad habits feed on then cause more aggressive and treatment-resistant cancers.
Here are some of the main factors that may be behind the increased rates of cancer among young people.
Vaping and poor oral hygiene
London-based private clinic Pure Periodontics has witnessed a surprising increase in gum disease in younger patients. They attribute this to diets full of sugar and acid, along with the rise of vaping under 40, a habit that inhibits blood flow to the gums, increases susceptibility to infection and makes healing more difficult.
All this promotes the growth of a certain strain of bacteria called Fusobacterium nucleatum (F. nucleatum) which has been linked to a range of cancers, including breast, colorectal and head and neck cancers.
“It is a very sticky insect that sticks to the surface of the teeth and gums and lets in other bad bacteria,” says Dr Tim O’Brien, a medical oncologist and researcher at Queen’s University Belfast.
With poor oral hygiene, these bacteria can multiply, enter the bloodstream and gain access to various organs. When these microbes invade tumors at an early stage, they can actively interfere with chemotherapy and radiotherapy, allowing the cancer to grow and spread.
“Fusobacterium can contribute to chemotherapy, but also to radiation resistance,” says O’Brien. “It thrives in the tumor environment, so it is in its best interest that the tumor survives. So it disrupts the process by which chemotherapy causes cancer cells to destroy themselves, and it can also disable immune cells that are trying to destroy the tumor.”
High intake of processed meat
According to the journal Nature, stomach cancer was one of the sharpest increases in cancer rates under the age of 50.
One of the best known risk factors for stomach cancer are bacteria Helicobacter pylori (H. pylori) which is believed to account for around 40 percent of cases in Britain. H. pylori lives in the mucous layers that line the stomach and contributes to conditions such as atrophic gastritis, the chronic inflammation and thinning of the stomach lining, which can then develop into cancer.
Research has shown that a diet high in processed meats, such as sausages, bacon and burgers, can increase its prevalence H. pylori in the stomach.
Professor Andrew Beggs, consultant colorectal surgeon at the University of Birmingham, describes the link between such microbes and lifestyle factors as ‘essential pieces of a puzzle’.
“You have these bacteria and an unhealthy lifestyle with excessive red meat, alcohol and smoking, and some people may also have a genetic predisposition that increases their risk,” he says. “If you add all those factors together, it leads to a large increase in the risk of cancer.”
Oral sex
It’s not just bacteria that can cause cancer cases, viruses have also been linked to various forms of the disease. Specialists in Britain have described rising rates of oral cancer, particularly in 40 to 49 year olds, with half of these cases linked to a strain of the sexually transmitted human papillomavirus (HPV) known as HPV-16, which can are passed on through oral sex.
One possibility could be a greater number of casual sexual partners, with a study in the journal Cancer showing that kissing, and especially deep kissing, is also linked to an increased risk, with those with ten or more kissing partners twice as likely to develop an HPV. -related cancer.
Ultra-processed foods
The F. nucleatum Bacteria not only make cancer more resistant to treatment, but can also actively cause the disease, especially in the intestines. A new study in Nature published last week, found that mice fed a certain subspecies of this bacteria developed precancerous intestinal growths and accelerated tumor formation compared to normal mice.
Researchers who have studied this bacterium and certain species E.coli which have also been linked to colorectal cancer, believe that a diet high in ultra-processed foods may alter the composition of the gut microbiome in a way that allows these species to flourish, increasing the risk of cancer progression through a number of mechanisms.
“Some bacteria cause intestinal cells to acquire stem cell-like properties, which increases the risk of cancer formation at the cellular level,” says Dr Meera Patel, researcher in the Colorectal & Peritoneal Oncology Lab at the University of Manchester.
“There is also a theory that certain bacteria can damage the vascular barrier of the gut, stopping the spread of bacteria from your colon to your wider circulation. If you have a disrupted intestinal barrier, tumor cells can move out of the colon and metastasize to the intestines. other organs.”
Excessive alcohol
However, there are other cases of cancer in young people where microbial involvement has not yet been established.
For example, testicular cancer is the most common solid tumor cancer diagnosed in young men, and according to the NHS, the number of cases identified each year in Britain has doubled since the 1970s for reasons that cancer specialists are still trying to understand. to understand.
Family history is one of the biggest risk factors for this type of cancer, but some population studies have also shown a link between excessive drinking and a form of the disease called testicular germ cell carcinoma.
Young men who consume 14 or more alcoholic drinks per week appear to be at greater risk, in addition to a diet high in fat, red meat and dairy products and low in fruits and vegetables.
New treatments
However, the emerging link between microbes and various forms of early-onset cancers in young people could lead to new targeted treatments, such as phage therapy, in which patients are given specially designed viruses that are programmed to feed on a particular species of problematic bacteria. or targeted vaccines.
“You could vaccinate mice before infecting them with it F. nucleatum and see if it makes a difference in terms of the outcome of polyps and cancers,” says Beggs. “If that is the case, there will be a strong argument for conducting a phase one trial in humans to see if this will reduce the incidence of colorectal cancer.”
O’Brien predicts that a tumor’s specific microbial composition could be used to determine treatment decisions in the coming years.
“We’re not using that information right now, but I think in the future we can obtain it and use it to decide whether this is a particularly aggressive tumor and whether the patient needs a higher dose of chemotherapy.” he says.
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