Helicobacter pylori (H. pylori) infection is strongly associated with certain stomach cancers, but most people with H. pylori do not develop cancer.
The relationship usually develops over many years:
H. pylori infection → chronic stomach inflammation (gastritis) → stomach lining damage/atrophy → intestinal metaplasia → dysplasia → gastric cancer
H. pylori is particularly associated with gastric adenocarcinoma, the most common type of stomach cancer.
It can also cause gastric MALT lymphoma, a cancer involving immune cells in the stomach lining.
Importantly, treating H. pylori with appropriate antibiotics can reduce the future risk of stomach cancer, especially when treatment occurs before advanced precancerous changes have developed.
H. pylori is not a general cause of all GI cancers. Its strongest established cancer relationship is with stomach cancer and gastric MALT lymphoma.
If someone tests positive for H. pylori, treatment is generally recommended, followed by a test of cure (usually a urea breath test or stool antigen test) after treatment. Symptoms such as unexplained weight loss, persistent vomiting, black/tarry stool, vomiting blood, anemia, difficulty swallowing, or persistent upper-abdominal pain warrant medical evaluation.
How H. pylori can eventually cause stomach cancer
Think of the stomach lining as a protective wall.
H. pylori can live in the mucus covering that wall for many years.
1. H. pylori infects the stomach lining
The bacteria attach to cells lining the stomach. They produce substances such as urease that help them survive stomach acid.
2. The immune system creates chronic inflammation
Your immune system continuously tries to eliminate the bacteria. If H. pylori remains for years, this produces chronic gastritis.
3. Long-term inflammation damages stomach cells
Inflammatory chemicals and oxidative stress repeatedly injure the cells. The stomach continually repairs and replaces damaged cells.
4. Normal stomach glands can gradually disappear
Long-standing inflammation can cause atrophic gastritis, meaning some normal acid-producing stomach glands are lost.
5. Intestinal metaplasia may develop
Some stomach cells change into cells resembling those normally found in the intestine. This is called intestinal metaplasia. It is considered a precancerous change, but it does not mean the person has cancer.
6. Dysplasia can occur
Additional DNA damage and abnormal cell growth may eventually produce dysplasia, where cells become increasingly abnormal.
7. Gastric adenocarcinoma can develop
In a relatively small proportion of infected people, accumulated genetic and cellular changes eventually allow cells to grow uncontrollably and become stomach cancer.
So the classic progression is:
H. pylori → chronic gastritis → atrophic gastritis → intestinal metaplasia → dysplasia → gastric adenocarcinoma
This process usually takes many years or even decades, and most people with H. pylori never progress through all these stages.
Another cancer: MALT lymphoma
H. pylori can also continuously stimulate immune cells called B lymphocytes in the stomach. In some people, these cells eventually become abnormal and cause gastric MALT lymphoma.
Interestingly, when early MALT lymphoma is caused by H. pylori, eliminating the H. pylori can sometimes cause the lymphoma to regress, which illustrates how directly the infection can drive this particular cancer.
Why treating H. pylori matters
Eradicating the infection stops the continuing bacterial stimulus and substantially reduces chronic inflammation. This can lower future gastric-cancer risk, particularly when H. pylori is eliminated before extensive atrophy or intestinal metaplasia develops.
One important distinction: intestinal metaplasia or even chronic gastritis does not automatically mean someone will develop cancer. These findings indicate increased risk and may influence whether a gastroenterologist recommends additional surveillance.
Recently, I was working late into the night on a manuscript when I came across a sentence that gave me pause: cancer usually does not occur from an amazing incident; rather, it occurs due to gradual changes within cells over time.
The cells in our bodies divide, fix themselves, replace old cells, and so forth on a regular basis. In some instances, there are problems within this process that result in cancer developing. A mutation causes the cell to grow out of control, ignoring the natural inhibitions in the body and eventually turning into a tumor.
It is not always because of something the individual did. Things like age, genetic predispositions, natural mistakes, smoking, certain viruses, radiation, alcohol consumption, and others can lead to cancer development. Cancer can occur even though we are doing all the right things.
In fact, one of my doctors once told me bluntly: "Think of cancer not as something to be punished for, but as biology going off the script." This altered the way in which I thought about cancer prevention. Rather than focusing on trying to find ways to completely avoid cancer, I focused on the little things I could do every day.
One of the little things my doctor insisted I try to incorporate into my routine every day seemed to be so mundane as to not make any difference at all. However, I stuck with it anyway and realized that the mundane things are the ones that actually make a difference.
There isn’t a single cancer; it’s not one illness with one cause. Rather, it’s a very complex breakdown of cell regulation and knowledge about it is far more important than self-recrimination.
