A particular type of bacteria called Helicobacter pylori is responsible for a number of diseases, including ulcers and, more worryingly, stomach cancer. Recent results from a long-term study in China suggest that a short course of antibiotics and stomach acid inhibitors can effectively prevent cancer in infected people, even many years later.
H. pylori is a spiral-shaped bacterium that thrives in the acidic environment of the stomach by neutralizing the acid around it. It burrows into the mucous layer of the stomach and escapes the immune system. Although the bacteria are widespread and about two-thirds of the world’s population are carriers of this bacteria, most people do not develop ulcers or stomach cancer.
Why some people suffer severe consequences while others remain symptom-free is still the subject of ongoing research. Scientists are also looking for ways to prevent the development of more serious consequences, such as stomach cancer.
The discovery in the 1980s that H. pylori can cause ulcers revolutionized the medical treatment of this disease. Barry Marshall and Robin Warren, who made this discovery, received the Nobel Prize in Physiology or Medicine in 2005. Marshall drank a culture of H. pylori to prove that the bacteria could infect a healthy person and cause gastritis, which ultimately helped confirm H. pylori as the cause of stomach ulcers and stomach cancer.
However, it is still unclear why only a small proportion of the billions of people infected with H. pylori develop ulcers or cancer. The highest burden of disease is seen in East Asia, Latin America and Eastern Europe.
Previous small studies and observational studies, particularly in Japan, suggested that eradicating H. pylori could help prevent stomach cancer. Now, a large controlled trial provides solid evidence of the effectiveness of comprehensive screening and eradication efforts. The study, published in Nature Medicine, shows that reducing the prevalence of H. pylori in a population can lead to a significant decline in stomach cancer incidence over time.
In 2011, researchers in China conducted a large-scale study. They visited nearly a thousand villages and subjected over 180,000 people to a simple breath test. More than half of those infected tested positive for H. pylori. As part of the study, the infected people were divided into two groups: one received a 10-day treatment with antibiotics and stomach acid inhibitors to eradicate the bacteria, the other did not.
More than a decade later, the results were striking. The risk of stomach cancer fell by 13% in the treated group and by 19% in the group that had cleared the infection. In younger participants, particularly those under 45, cancer incidence and mortality fell even more significantly, suggesting that early intervention may be crucial in preventing cancer progression.
So what are the implications for India? The relationship between H. pylori infection and stomach cancer in India is complex. While infection rates in India are high, ranging from 50% to over 80% in different communities, stomach cancer rates do not always match this high prevalence.
In India, for example, stomach cancer is more common in the southern regions than in the north, suggesting that local factors (possibly dietary, environmental or genetic) play a role.
Treating all people infected with H. pylori may not be practical due to the costs associated with antibiotic treatments and the risk of antibiotic resistance. A more balanced approach could involve targeted intervention in people with ulcers and those at highest risk of developing gastric cancer.
Overall, the significance of the new study is that it shows that many lives could be saved by treating high-risk populations. The effect is likely to be greatest in countries and regions where stomach cancer is common, such as China, where the authors note that it is a “leading cause of cancer-related deaths.” In their research article, they estimate that by treating H. pylori, “it is reasonable to expect that more than 85,000 cases of stomach cancer could be prevented annually in China.”
Anirban Mahapatra is a scientist and author, most recently of the popular science book When The Drugs Don’t Work: The Hidden Pandemic That Could End Medicine. The views expressed are personal.
