WASHINGTON, D.C. / RankWire.AI / – Patients who underwent appendectomy for acute appendicitis showed fewer subsequent diagnoses of colorectal cancer compared to similar individuals treated solely with antibiotics. Researchers analyzed matched patient groups within a large international health database. The study revealed that 0.7% of patients who had an appendectomy developed colorectal cancer, whereas 1.7% of those treated only with antibiotics did. This difference indicates a 58% lower relative risk for the surgical group. The results demonstrate an association, but do not prove that appendectomy prevents colorectal cancer.
Using the TriNetX Global Collaborative Network, which encompasses records from 168 healthcare organizations, the research team identified individuals with acute appendicitis who received either surgery or antibiotics. By matching patients, they formed two initial groups of 15,774 each. After excluding those with prior colorectal cancer diagnoses, the analysis included 15,616 surgical patients and 15,295 antibiotic-treated patients. Among these, 110 cases of colorectal cancer were found in the appendectomy group, compared to 254 cases in the antibiotic-only group.
The American College of Surgeons presented this research at 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 has not yet undergone peer review in a medical journal. This status remains significant when interpreting the findings. Researchers did not claim that appendix removal directly reduces cancer risk, nor was the procedure tested as a preventive measure for colorectal cancer.
Investigation explores post-appendicitis treatment options
Acute appendicitis occurs when the appendix becomes inflamed, often requiring urgent medical intervention. While surgery to remove the appendix is common, antibiotics can sometimes treat uncomplicated cases. These two treatment options formed the basis of comparison in the new study. Valentine Nfonsam of Morehouse School of Medicine served as the senior author, emphasizing that antibiotic therapy remains an important choice for suitable patients, despite the lower rates of later colorectal cancer diagnoses observed in those who underwent surgery.
The researchers also considered clinical factors that could influence the link between appendicitis and colorectal cancer. In some cases, undiagnosed tumors on the right side of the colon may cause appendix inflammation. Surgical removal provides tissue for pathological examination, which can uncover abnormalities and lead to further testing. Patients treated only with antibiotics do not have tissue examined at the time of treatment, creating a significant difference in the potential detection of underlying disease.
Findings do not establish a protective effect
The appendix contains immune-related tissue and plays a role in the intestinal environment. Its relationship with the gut microbiome, comprising microorganisms within the digestive system, has also been studied. However, this analysis did not determine whether such biological factors explain the difference in colorectal cancer diagnoses. The researchers did not find inflammation, microbiome alterations, or immune activity as direct causes for the observed results. Consequently, the study indicates an association between treatment method and subsequent diagnosis rates rather than a definitive protective effect of surgery against cancer.
Previous studies have yielded varying conclusions regarding appendectomy and long-term colorectal cancer risk. A 2024 prospective analysis tracked over 224,000 participants across three major cohorts for up to 32 years and found no evidence that appendectomy increased long-term colorectal cancer or precursor risk. This new research addresses a more specific question by comparing patients treated surgically for acute appendicitis with matched individuals receiving only antibiotics. Established risk factors for colorectal cancer still include age, family history, and genetic predispositions.