WASHINGTON, D.C. / RankWire.AI / – Patients who underwent appendix removal for acute appendicitis had fewer later colorectal cancer diagnoses than patients treated only with antibiotics, according to new research. The retrospective study compared matched groups drawn from a large international health database. Researchers found colorectal cancer in 0.7% of patients who had an appendectomy. The rate reached 1.7% among those who received antibiotics alone. That difference corresponded to a 58% lower relative risk in the surgery group.
Researchers used the TriNetX Global Collaborative Network, which contained data from 168 healthcare organizations. They identified patients with acute appendicitis who received either surgery or antibiotic treatment. After matching patients by relevant characteristics, each initial group contained 15,774 people. The final analysis included 15,616 appendectomy patients and 15,295 antibiotic-treated patients after researchers excluded earlier colorectal cancer diagnoses. Records showed 110 colorectal cancer cases after appendectomy and 254 cases after antibiotic-only treatment.
Researchers presented the findings at the American College of Surgeons Clinical Congress 2026, held in Washington from Sept. 26 through Sept. 29. The Scientific Forum program committee reviewed and selected the research abstract. However, no medical journal has yet peer reviewed the study. That distinction limits the conclusions that can be drawn from the findings. The study identifies an association between treatment choice and later colorectal cancer diagnosis, but it does not establish that appendix removal prevents colorectal cancer.
Study compares surgery with antibiotic treatment
Acute appendicitis occurs when the appendix becomes inflamed. The appendix sits near the junction of the small and large intestines. Doctors traditionally treat many cases by surgically removing the organ, a procedure known as appendectomy. Antibiotics have also become an accepted treatment for selected patients. Senior author Valentine Nfonsam, a professor and executive vice chair of surgery at Morehouse School of Medicine, said antibiotic treatment remains an important option despite the study’s findings.
The researchers also examined factors that could affect how colorectal cancer appears after appendicitis treatment. Appendicitis can sometimes occur in a patient who already has an undiagnosed colorectal tumor. A tumor on the right side of the colon can obstruct the appendix and trigger inflammation. Surgery also gives clinicians tissue for pathological examination after they remove the appendix. That examination can reveal abnormalities and lead doctors to conduct additional diagnostic testing that does not occur immediately with antibiotic-only treatment.
Findings do not establish cancer prevention
The appendix contains lymphoid tissue and participates in immune activity within the intestinal system. Research has also linked the organ to the gut microbiome, which includes bacteria and other microorganisms in the digestive tract. The latest study did not determine whether those biological functions explain the difference in colorectal cancer diagnoses. It also did not establish whether inflammation or microbial changes caused the observed association. Researchers therefore stopped short of describing appendectomy as a cancer prevention measure.
Earlier research has produced differing results on the relationship between appendectomy and colorectal cancer. A 2024 prospective analysis followed more than 224,000 participants across three large cohorts for as long as 32 years. It found no evidence that an appendectomy increased long-term colorectal cancer risk or the risk of colorectal precursors. The new study addresses a different question by comparing appendicitis patients treated surgically with similar patients receiving antibiotics alone. Researchers said age, family history and genetic predisposition remain established factors when assessing colorectal cancer risk.