WASHINGTON, D.C. / RankWire.AI / – In a large-scale international study, patients who had their appendix removed due to acute appendicitis showed a significantly lower rate of subsequent colorectal cancer diagnoses compared to those treated solely with antibiotics. Researchers analyzed matched patient groups within an extensive health database. The data revealed that 0.7% of patients who underwent an appendectomy developed colorectal cancer, whereas 1.7% of those who received only antibiotics did. This difference indicates a 58% decrease in relative risk for patients who had surgery. It is important to note that these findings show an association, not proof that appendectomy directly prevents colorectal cancer.
The investigation utilized the TriNetX Global Collaborative Network, which encompasses records from 168 healthcare organizations. Researchers identified individuals diagnosed with acute appendicitis who received either surgical intervention or antibiotics. After matching, two initial cohorts of 15,774 patients each were formed. Following the exclusion of patients with prior colorectal cancer diagnoses, the analysis included 15,616 surgical patients and 15,295 antibiotic-treated patients. Within these groups, there were 110 cases of colorectal cancer in the appendectomy group and 254 in the antibiotic-only group.
The American College of Surgeons highlighted this research during its 2026 Clinical Congress in Washington, held from Sept. 26 through Sept. 29. The study was included in the Scientific Forum program after review for conference presentation, but it has not yet undergone peer review in a medical journal. This status remains significant when interpreting the findings. Researchers did not assert that removing the appendix directly reduces cancer risk, nor did the study evaluate appendectomy as a preventive measure against colorectal cancer.
Analysis of treatment options following appendicitis
Acute appendicitis occurs when the appendix becomes inflamed and often requires urgent medical care. Typically, doctors remove the appendix surgically, though antibiotics can be effective for certain uncomplicated cases. These two treatment methods formed the basis of comparison in the new research. Valentine Nfonsam from Morehouse School of Medicine served as the senior author. He emphasized that antibiotic therapy remains a vital option for suitable patients, despite the lower rate of later colorectal cancer diagnoses observed in those who underwent surgery.
The study also examined clinical factors that might influence the link between appendicitis and colorectal cancer. In some cases, an undiagnosed tumor in the right side of the colon may cause inflammation of the appendix. Surgical removal allows for tissue examination by a pathologist, which can detect abnormalities and lead to further diagnostic tests. Patients treated solely with antibiotics do not have this tissue analyzed at the time of treatment, creating a significant difference in how potential disease might be identified.
Findings do not establish a protective effect against cancer
The appendix contains tissue involved in immune responses and is part of the gut environment. Researchers have also explored its connection to the gut microbiome, which comprises microorganisms within the digestive system. The current analysis did not determine whether these biological factors explain the variation in colorectal cancer diagnoses. Additionally, the study did not establish inflammation, microbiome alterations, or immune activity as causal factors for the observed association. Consequently, the findings suggest a correlation between treatment type and later cancer diagnosis rates rather than a confirmed protective benefit from appendectomy.
Previous studies have produced conflicting results regarding the relationship between appendectomy and long-term colorectal cancer risk. A prospective study in 2024 tracked over 224,000 participants across three major cohorts for up to 32 years, finding no evidence that appendectomy increases the long-term risk of colorectal cancer or precancerous conditions. This new research narrows the focus by comparing patients treated surgically for acute appendicitis with matched patients who received only antibiotics. Established risk factors for colorectal cancer continue to include age, family history, and inherited genetic predispositions.