Patients who had surgery for an inflamed appendix had a significantly lower risk of developing colorectal cancer than those treated with antibiotics, according to an analysis of more than 30,000 cases.

In the study, researchers reviewed data on 15,774 patients diagnosed with acute appendicitis who underwent appendectomy and another 15,295 who were treated with antibiotics alone. Colorectal cancer was later diagnosed in 0.7 per cent of the appendectomy group and in 1.7 per cent of the antibiotics group.

After accounting for individual risk factors, appendectomy was associated with a 58 per cent lower relative risk of a subsequent colorectal cancer diagnosis. The results were presented at the American College of Surgeons Clinical Congress in Washington.

Surgery was once the standard of care for acute appendicitis. "Management of the condition has changed significantly over the last decade, and antibiotic therapy is now an accepted option," said study leader Dr. Valentine Nfonsam of Morehouse School of Medicine in Atlanta.

The appendix was once thought to be useless, but emerging research suggests it may play a role in the intestinal immune system and the gut microbiome. Whether persistent inflammation or changes in the microbiome contribute to cancer development is biologically plausible, but the study was not designed to answer that question, Nfonsam said.