Acid reflux drugs may more than double risk of stomach cancer

Acid reflux and heartburn drugs called proton pump inhibitors are some of the most widely used in the world, but a new study found that long-term use can increase stomach cancer risks by almost 250%.

For short-term treatment, PPIs have proved safe and effective in suppressing stomach acid production. But, for a small percentage of people who carry a bacterium called Helicobacter pylori, the risk of developing stomach cancer shoots up when they take a PPI for an extended period of time, according to the study. About half of the world's population has this bacteria naturally occurring inside of them — but for some, the drug and bacterium combination could lead to cancer.

"Proton pump inhibitors are an important treatment of Helicobacter pylori infection and have good safety records for short-term use," the study's co-author Ian Wong told the University College London News. "However, unnecessary long-term use should be avoided."

The researchers looked at health data for over 63,000 people who took PPIs and other antibiotics to fight a H. pylori infection. For three years, just over 3,000 people continued to take PPIs while almost 22,000 other patients used alternatives.

Of the original group of 63,000, 153 people eventually developed stomach cancer but those on PPIs were 2.44 times more likely to get cancer and those on alternative drugs had no increased risk. And those on PPIs daily during this time period had up to an eight-fold greater risk of stomach cancer, according to the study.

"Interestingly, the authors found no such correlation between gastric cancer risk and long-term treatment with other anti-suppressive drugs," gastrointestinal infection researcher Richard Ferrero told Science Alert. "The work has important clinical implications as PPIs, which are among the top 10 selling generic drugs in the US, are commonly prescribed to treat heartburn."

The study notes that it's important to keep in mind that although this heightened risk is alarming, it only leads to an occurrence in a small number of people — about four in every 10,000 stomach cancer cases. And the researchers aren't sure exactly why the connection exists.

"The most plausible explanation for the totality of evidence on this," pharmacoepidemiologist Stephen Evans told the website, "is that those who are given PPIs, and especially those who continue on them long-term, tend to be sicker in a variety of ways than those for whom they are not prescribed."