The bacterium helicobacter pylori (H. pylori) is the pathogen responsible for the largest number of cancer cases worldwide, according to a report by the American Association for Cancer Research (AACR). 2.2 million cases of cancer are attributed to bacterial or viral infections.
A common bacteria is the cause of most cancers. PHOTO: Shutterstock
The bacterium caused more than 800,000 cases of cancer in 2018, and approximately 30% to 40% of Americans have an infection with this pathogen at some point, according to the American Association for Cancer Research, cited by News.ro.
When we think of the causes of cancer, factors such as genetics and lifestyle come to mind, but some pathogens can also lead to cancer.
The American Association for Cancer Research shows in the recently published report – “Cancer Progress Report 2024. Preventing and eliminating infection with pathogens that cause cancer” – that 13% of cancer cases worldwide, i.e. 2.2 million, are attributed to bacterial infections or viral.
However, the pathogen responsible for the largest number of cancer cases worldwide is Helicobacter pylori, better known as H. pylori.
The bacterium was responsible for about 810,000 cancer cases in 2018, the most recent year for which data is available.
By comparison, HPV led to 690,000 cases that year, followed by hepatitis B with 360,000 cases.
Symptoms of an infection with this bacteria include vomiting, weight loss, trouble swallowing, and severe heartburn, but many infections can be asymptomatic.
What is H. Pylori and how does it cause cancer?
H. pylori is a bacteria that many people carry in their stomachs. About 30% to 40% of Americans have an H. pylori infection at some point. The bacteria can cause ulcers to form in the stomach or small intestine and can also lead to gastritis, which is an inflammation of the lining of the stomach.
Over time, this can develop into more serious diseases, said Dr. Linda Cummings, a gastroenterologist at the Cleveland Clinic University Hospitals Medical Center and a professor at Case Western Reserve University School of Medicine.
“In some people who are susceptible due to genetic factors, lifestyle or characteristics of the H. pylori strain itself, this inflammation leads to precancerous changes in the stomach lining that can eventually progress to cancer“, she said in a statement.
H. pylori can increase the risk of two types of cancer: mucosa-associated lymphoid tissue (MALT) lymphoma, a form of non-Hodgkin’s lymphoma that affects the stomach, and a type of gastric cancer called adenocarcinoma, which originates in the lining of the stomach.
According to the American Cancer Society, 90 to 95% of all stomach cancers are adenocarcinomas.
The bacterium H. pylori is the strongest risk factor for gastric cancer, Dr. Cummings pointed out. People with an infection with this bacterium have a two to six times greater risk of developing gastric cancer and MALT lymphoma compared to those who are not infected, according to the US Centers for Disease Control and Prevention (CDC).(4)
It is important to remember that, for most people, H. pylori infection does not lead to cancer. “Of all people infected with H. pylori, it is thought that about 1% to 3% will develop cancer“, stated Dr. Cummings.(5)
How is H. pylori taken?
Although not enough is known about the transmission of the bacteria, Dr. Cummings says that H. pylori can be spread through bodily fluids.
“Since H. pylori can be found in faeces (stool), gastric juice, saliva and dental plaque, it could potentially be spread through oral secretions or vomit”she said.
Person-to-person transmission in the household is likely because a child’s risk of H. pylori is higher if a parent or sibling is infected, experts say.
Most people with H. pylori probably contract the infection in childhood, Dr. Cummings added. Transmission is often associated with poor hygiene and sanitation, crowded living conditions and inadequate water supplies.
In general, H. pylori infections are significantly more common in low- and middle-income countries than in high-income countries.
However, in the United States, there are hotspots, including Native American communities, where the rate of H. pylori infection is higher than the 36% in the general population.
The prevalence of H. pylori is 62% among Navajo adults in Arizona, for example, and 75% among the indigenous population of Alaska.
Gastric cancer incidence is highest in East Asia, Eastern Europe and Andean Latin America, while mortality is highest in East Asia, Andean Latin America and Central Asia.
“In some countries in Asia with high rates of gastric cancer, universal gastric cancer screening by endoscopy or an X-ray test starting at age 40 or 50 is recommended”said Dr. Cummings.
Symptoms and diagnosis
Some people with an H. pylori infection have no symptoms, while others may experience abdominal discomfort after eating. Vomiting, weight loss, difficulty swallowing and severe heartburn are also signs of an H. pylori infection, the doctor said.
“Black, foul-smelling stools with increased frequency may result from a bleeding ulcer caused by H. pylori” she added.
Since an H. pylori infection can be asymptomatic, testing is the only way to determine the presence of the bacteria.
There are four ways to test for H. pylori: a urea breath test (based on Helicobacter pylori’s ability to produce an enzyme called urease. This enzyme breaks down the urea administered during the test, leading to the release of ammonia which is released through the breath Thus, the test measures the level of ammonia in the patient’s breath), a fecal antigen test, an upper endoscopy and a blood test.
However, Dr. Cummings said the blood test is rarely used in the US because a person can test positive even after the bacterial infection has been successfully treated.
Screening for H. pylori is not recommended in the United States, but Dr. Cummings suggests testing people who:
shows signs or symptoms of an infection with H. pylori;
have or have had an ulcer in the stomach or small intestine;
live in the same house as a person who has an H. pylori infection;
have a family history of H. pylori, gastric cancer or peptic ulcer;
They have MALT or iron deficiency anemia;
regularly take non-steroidal anti-inflammatory drugs, which increase the risk of ulcers;
Treatment of H. pylori infection
According to experts, H. pylori infections usually do not go away without treatment and have become increasingly difficult to treat because the bacteria has developed resistance to some antibiotics.
“This resistance has led to increasingly complex treatment regimens”explained the doctor.
Currently, infections are treated for two weeks with several medications, including drugs to suppress stomach acid and antibiotics. Some regimens also include bismuth-containing compounds.
Some people may need to take a second or even third course of antibiotics to clear the infection. Although special tests can be done to determine which antibiotics H. pylori may be resistant to, these tests are not widely available.
How can H. pylori infections be prevented
Since the transmission of H. pylori is not well understood, it is thought to be most often acquired in childhood, so preventing the spread of the bacteria can be a challenge.
“An infected sibling, an infected mother, or an infected father are strong risk factors for H. pylori”says Dr. Cumming.
Strategies that can help prevent the spread of H. pylori include washing your hands frequently, especially after using the toilet, avoiding sharing utensils and drinking glasses or bottles, and drinking water from a clean and safe source.
