Bacteria present in the stomachs of about half of adults worldwide may provide protection from cancer of the esophagus, researchers disclosed earlier this year.A research team at Stanford University studied the medical records of over 130,000 patients. They found that patients with Helicobacter pylori in their stomachs had a greater than 70% lower chance of developing esophageal adenocarcinoma than those without the bacteria.
However, the news is not without a downside. Doctors have been trying to eliminate H. pylori with antibiotics since the mid-1980s. At that time, they discovered it was a main cause of peptic ulcers and stomach cancer.
H. pylori is an unusual bacteria — the only known bacteria that can cause cancer and one of the only bacteria that can survive in the acidic environment of the stomach. The corkscrew-shaped bacteria drills itself into the stomach lining and, while nourishing itself, reduces the stomach’s ability to produce acid. This often leads to peptic ulcers, non-Hodgkins lymphoma of the stomach and gastric adenocarcinoma.
As the number of people with H. pylori has decreased, however, the number of people with acid reflux disease, or GERD, has increased. When the bacteria no longer inhibits the production of stomach acid, reflux of that acid leads to frequent heartburn and Barrett’s esophagus. People who experience acid reflux at least once a week are five to eight times more likely to develop esophageal adenocarcinoma, while patients with Barrett’s esophagus are at least 30 times more at risk for the cancer.
The rate of esophageal adenocarcinoma is increasing worldwide at about 8% per year in the developed world (where antibiotics to treat H. pylori are more commonly used). Even with the increased risk, esophageal adenocarcinoma is still only diagnosed in about 1% of U.S. cancer patients annually. Currently about one in every 10,000 people is diagnosed with this form of cancer each year. White males are the most at risk population.
Meanwhile, gastric cancer (caused in large part by H. pylori) is the second most common cancer worldwide. At the beginning of the last century, stomach cancer was the most common form of cancer in the U.S.; although its incidence has decreased in the developed world, it is still much more common than esophageal cancer.
H. pylori is probably the most common bacterial infection in people and exists in more than half of the world’s population. Most people with H. pylori in their stomachs acquired the bacteria in early childhood through oral contact with the body fluids of an infected person. With improved sanitation and the increased use of antibiotics in early childhood, the infection rate is decreasing in developed nations. Not all strains of the bacteria are harmful—80 to 90% of carriers develop few or no symptoms—despite their ability to survive for decades in the harsh environment of the stomach.
No link has been found between H. pylori bacteria and esophageal squamous cell carcinoma or other types of esophageal cancer.
