WASHINGTON, D.C. / RankWire.AI / – Patients who underwent appendix removal for acute appendicitis later recorded fewer colorectal cancer diagnoses than similar patients treated with antibiotics alone. Researchers compared matched patient groups in a large international health database. Colorectal cancer appeared in 0.7% of patients who had an appendectomy, compared with 1.7% of those who received antibiotics only. The difference represented a 58% lower relative risk among patients who underwent surgery. The findings show an association, not proof that appendectomy prevents colorectal cancer.
The research team used the TriNetX Global Collaborative Network, which included records from 168 healthcare organizations. Investigators identified people with acute appendicitis who received either surgical treatment or antibiotics. Matching produced two initial groups of 15,774 patients each. After excluding patients with earlier colorectal cancer diagnoses, researchers analyzed 15,616 surgical patients and 15,295 antibiotic-treated patients. They found 110 colorectal cancer cases in the appendectomy group and 254 cases among patients treated only with antibiotics.
The American College of Surgeons featured the research during its 2026 Clinical Congress in Washington, held from Sept. 26 through Sept. 29. The study appeared in the meeting’s Scientific Forum program after review for conference presentation. It has not undergone peer review in a medical journal. That status remains important when assessing the findings. Researchers did not conclude that removing the appendix directly lowers cancer risk, and the study did not test appendectomy as a colorectal cancer prevention procedure.
Study examines treatment paths after appendicitis
Acute appendicitis develops when the appendix becomes inflamed and often requires prompt medical treatment. Doctors commonly remove the appendix through surgery, while antibiotics can treat selected uncomplicated cases. The two approaches formed the basis of the comparison in the new research. Valentine Nfonsam of Morehouse School of Medicine served as the study’s senior author. He said antibiotic therapy remains an important treatment option for appropriate patients, despite the lower rate of later colorectal cancer diagnoses found in the surgical group.
Researchers also considered clinical factors that can complicate the connection between appendicitis and colorectal cancer. In some patients, an undiagnosed tumor in the right side of the colon can contribute to appendix inflammation. Surgical treatment also gives doctors removed tissue for examination by a pathologist. That process may reveal abnormalities and prompt additional diagnostic testing. Patients treated only with antibiotics do not undergo that tissue examination at the time of treatment, creating a meaningful difference in how possible disease can come to light.
Results stop short of proving cancer protection
The appendix contains immune-related tissue and forms part of the intestinal environment. Scientists have also studied its relationship with the gut microbiome, which includes microorganisms living in the digestive system. The latest analysis did not determine whether those biological features explain the difference in colorectal cancer diagnoses. Researchers also did not establish inflammation, microbiome changes or immune activity as causes of the observed result. For that reason, the study supports an association between treatment type and later diagnosis rates rather than a proven protective effect from surgery.
Previous research has reached different conclusions about appendectomy and long-term colorectal cancer risk. A 2024 prospective analysis followed more than 224,000 participants across three major cohorts for up to 32 years. That research found no evidence that appendectomy increased long-term colorectal cancer risk or colorectal precursor risk. The new study addresses a narrower question by comparing patients treated for acute appendicitis through surgery with matched patients treated only with antibiotics. Established colorectal cancer risk factors still include age, family history and inherited genetic factors.