WASHINGTON, D.C. / RankWire.AI / – Patients who had their appendix removed due to acute appendicitis showed a lower rate of subsequent colorectal cancer diagnoses compared to similar individuals treated solely with antibiotics. Researchers analyzed matched patient groups within a comprehensive international health database. The data revealed that 0.7% of those who underwent an appendectomy developed colorectal cancer, in contrast to 1.7% of patients who received only antibiotic treatment. This difference indicates a 58% reduction in relative risk among the surgical group. It is important to note that these findings show an association, not definitive proof that appendectomy prevents colorectal cancer.
The study utilized the TriNetX Global Collaborative Network, which aggregated records from 168 healthcare organizations. Researchers identified individuals diagnosed with acute appendicitis who either underwent surgery or received antibiotics, and after initial matching, two groups of 15,774 patients each were formed. Following the exclusion of patients with prior colorectal cancer diagnoses, the analysis focused on 15,616 surgical patients and 15,295 antibiotic-treated patients, uncovering 110 cases of colorectal cancer in the appendectomy group and 254 in the antibiotic-only group.
This research was highlighted by the American College of Surgeons 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 presentation at the conference but has not yet undergone peer review in a medical journal, which remains a crucial factor when evaluating the findings. The researchers emphasized that they did not conclude that removing the appendix directly reduces cancer risk, nor did the study test appendectomy as a preventive measure against colorectal cancer.
Investigation explores treatment options following appendicitis
Acute appendicitis occurs when the appendix becomes inflamed and often requires swift medical intervention. Typically, doctors opt for surgical removal, although antibiotics can be effective in treating uncomplicated cases. The two treatment strategies served as the basis for comparison in this investigation. Valentine Nfonsam of Morehouse School of Medicine served as the senior author, noting that antibiotic therapy remains a vital treatment choice for suitable patients despite the lower incidence of subsequent colorectal cancer diagnoses observed in the surgical group.
The researchers also examined clinical factors that might complicate the link between appendicitis and colorectal cancer. For instance, in some cases, an undiagnosed tumor on the right side of the colon could cause inflammation of the appendix. Surgical intervention allows for tissue removal and pathological examination, which can reveal abnormalities and prompt further diagnostic testing. Conversely, patients treated with antibiotics do not have tissue sampled at the time of treatment, which creates a significant difference in the potential to detect underlying disease.
Findings do not establish a direct protective effect against cancer
Since the appendix contains immune-related tissue and plays a role within the gut environment, scientists have also explored its connection to the gut microbiome, comprising microorganisms residing in the digestive tract. However, this analysis did not determine whether these biological factors could explain the variation in colorectal cancer diagnoses. The researchers did not establish inflammation, microbiome alterations, or immune responses as causal factors for the observed outcomes. Therefore, the study indicates an association between treatment type and later cancer diagnoses but does not prove that appendectomy offers protection from colorectal cancer.
Previous studies have yielded differing conclusions regarding the relationship between appendectomy and long-term colorectal cancer. A 2024 prospective analysis, tracking over 224,000 participants across three major cohorts for up to 32 years, found no evidence that appendectomy increased the risk of long-term colorectal cancer or precursor lesions. This recent research narrows its focus to comparing patients treated surgically for acute appendicitis with those receiving only antibiotics, while acknowledging that established risk factors for colorectal cancer include age, family history, and inherited genetics.