What Is the Main Idea?

Helicobacter pylori (H. pylori) is a type of bacteria that can cause infection in the stomach. It is known to be connected to the development of gastric cancer, one of the most common cancers worldwide.

Due to these known connections between H. pylori and the development of gastric cancer, it would be reasonable to think that, for someone with gastric cancer, the presence of H. pylori is undesired and that it might impair treatment and survival. Indeed, current advice focuses on treating H. pylori infection when gastric cancer surgery takes place. However, it is possible that the almost opposite may be true – that the presence of H. pylori infection might in fact be connected with better results for gastric cancer treatment, as shown by the authors of the research paper Helicobacter pylori Infection as a Predictor of Treatment Outcomes of Gastric Cancer: A Systematic Review and Meta-Analysis” published in the journal Digestive Diseases.

What Else Can You Learn?

You can understand how a meta-analysis can be important to answering research questions, and also learn a little about the biology of cancer cells.

Take-Home Message

Patients with gastric cancer who also have H. pylori infection have better survival, regardless of treatment choice. Researchers need to find out more about the connection, and about how it affects treatment choices.

What Did the Researchers Do?

The researchers carried out a meta-analysis to study the effect of H. pylori infection in gastric cancer treatment.

What Is a Meta-Analysis?

A meta-analysis is the use of statistical techniques to combine the results of several research studies.

Why Is a Meta-Analysis Helpful?

Combining results of small studies together can lead to more sound statistics and consequently more confident conclusions.

How Did the Researchers Carry Out This Meta-Analysis?

The researchers identified 21 suitable studies which were found through a scientific process of database searching and criteria-based elimination, and represented 5,787 patients in total.

They examined the survival details of these patients with gastric cancer, comparing those with and without H. pylori infection. They recorded different categories of survival, such as overall survival and disease-free survival. They also analysed details regarding treatment (e.g., surgery, chemotherapy, or a combination).

What Details Did the Researchers Find?

The researchers found that the patients with H. pylori infection had better overall or disease-free survival, thus better results. Specifically, those patients with H. pylori who had surgery combined with chemotherapy (medication) had the best results.

Why Do Patients with Gastric Cancer with H. pylori Infection Have Better Survival?

  • The first possibility is that long-lasting pylori infection leads to high levels of microsatellite instability (MSI). MSI is when a cell loses its ability to self-repair. High MSI in a cancer cell makes it easier for immune cells and immunotherapy to “spot” and respond to these cancer cells, thus increasing treatment effectiveness and prognosis.
  • The second hypothesis is that pylori may influence the immune system to better target gastric cancer cells. In other words, the presence of H. pylori bacteria can result in activation of immune responses that might not otherwise happen.
  • Thirdly, since a higher rate of pylori has been found in early gastric cancer samples compared to advanced gastric cancer samples, the absence of H. pylori may actually indicate a more serious disease, which would have poorer results.
  • Finally, through complex mechanisms, patients with pylori infection respond better to chemotherapy (medication), thus also giving a better result.

Why Are These Findings Important?

For patients with a gastric cancer diagnosis, and their clinicians, the results from this meta-analysis may help them to understand treatment options or make choices. The results may also initiate a positive perspective towards the presence of H. pylori infection, which may previously have been viewed solely as a guilty contributor.

What Are the Next Steps?

For researchers, the next steps are to better understand the mechanisms and interactions between H. pylori and gastric cancer treatment, in particular with regards to decisions on H. pylori eradication treatment and the combining of surgery and chemotherapy.

Note: This post is based on an article that is not open access; i.e., only the abstract is freely available. In order for you to still learn about the outcome, we summarized the content of this article for you.

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