A widely available and inexpensive diabetes drug, metformin, costing as little as 2p per tablet, has shown significant potential in cutting the risk of oesophageal cancer by more than a third, according to a new study. Metformin is currently prescribed to millions worldwide to manage blood sugar levels in individuals with type 2 diabetes. Leading oncologists now believe this drug could play a crucial role in cancer prevention.

Published in the journal JAMA Network Open, the findings suggest that individuals at high risk of oesophageal cancer, such as those suffering from long-term acid reflux, could potentially be prescribed metformin as a protective measure. Professor Shai–Hau Xie, an expert in gastrointestinal cancers, commented on the clinical significance, stating that the observed association between metformin use and a significantly decreased risk of oesophageal cancer indicates a possible role for the drug in both cancer prevention and treatment strategies.

Oesophageal cancer, affecting the food pipe, is a growing concern, with its incidence closely linked to risk factors like obesity, poor diet, smoking, alcohol consumption, and chronic acid reflux. Conditions such as Barrett's Oesophagus, where abnormal cells develop in the oesophagus often due to prolonged acid reflux, also elevate the risk of this disease. Metformin has garnered attention as a potential treatment due to previous studies suggesting its ability to inhibit the reproduction of cancer cells. The drug is known to lower insulin levels, a hormone that can facilitate the multiplication of malignant cells.

The latest research, conducted by experts at Karolinska University Hospital in Stockholm, tracked over 13,000 oesophageal cancer patients and matched controls between 1994 and 2023. Participants were part of the Nordic Gastric and Oesophageal tumour study, which involved data from Denmark, Finland, Iceland, Norway, and Sweden. The study meticulously adjusted for potential confounding factors including tobacco use, alcohol consumption, use of anti-inflammatory painkillers like ibuprofen, and statin use.

On average, patients were diagnosed with oesophageal cancer around 70 years old, with a majority having a history of heavy smoking and drinking compared to the control group. Of the 13,050 cancer patients in the final study, 725, or just under six percent, were metformin users. In contrast, approximately eight percent of cancer-free participants were using the blood-sugar-lowering drug, leading researchers to hypothesize its protective effect. The study concluded that metformin could lower the risk of developing this deadly disease by an impressive 36 percent compared to non-use.

Intriguingly, metformin use was associated with lower odds of oesophageal squamous cell carcinoma (OSCC) regardless of sex, age, smoking status, alcohol consumption, and the use of NSAIDs and statins. The protective effect was particularly pronounced in participants receiving higher doses of the drug, defined as more than 1,278 daily doses over a five-year period. The research team emphasized that these findings provide a strong rationale for investigating metformin as a preventive option for high-risk individuals, such as those with precancerous lesions.

Furthermore, the results suggest a potential benefit in examining whether metformin medication could improve survival rates following curative treatment for OSCC, as many patients currently experience tumour recurrence and death within a few years post-treatment. While adjuvant treatment with metformin could potentially reduce this risk, the researchers caution that current evidence remains limited. They stressed the necessity for additional observational research, followed by rigorous clinical trials, before metformin can be recommended for these specific purposes.

In the UK, approximately 9,300 people are diagnosed with oesophageal cancer each year, according to Cancer Research. The disease is often difficult to detect early because its symptoms, such as persistent acid reflux, can be easily mistaken for indigestion, leading to diagnosis at an advanced stage. Acid reflux, which occurs when stomach acid irritates the oesophageal lining and increases the risk of abnormal cell growth, has long been linked to an elevated risk of the disease. The new findings offer hope that metformin could help protect individuals suffering from recurring heartburn and other risk factors.