Appendectomy may be associated with a reduced risk of a colorectal cancer subtype positive for the tumor-promoting Fusobacterium nucleatum bacteria, according to a recent study published by Kawamura et al in the Annals of Surgery.
Background
Despite being historically dismissed as an unnecessary organ, the appendix is now thought to play a role in the immune system. However, researchers don’t currently have a clear understanding of how its removal to treat appendicitis may affect long-term human health.
“Appendicitis is a painful and often urgent condition that predominantly affects teens and young adults, and appendectomies are the go-to treatment. However, the long-term effects of this procedure on the gut microbiome and, in turn, risk of colorectal cancer have been unclear,” explained senior study author Shuji Ogino, MD, PhD, a physician and researcher in the Department of Pathology at Brigham and Women’s Hospital. “We found that [patients] who had undergone appendectomies had a significantly lower risk of acquiring this subtype of colorectal cancer,” he added.
F nucleatum has been previously implicated in colorectal carcinogenesis.
Study Methods and Results
In the recent study, investigators used data from two large prospective cohort studies—the Nurses’ Health Study and the Health Professionals Follow-up Study—to examine the outcomes of 91,975 female patients aged 30 to 55 years and 47,431 male patients aged 40 to 75 years, respectively, who reported the presence or absence of an appendectomy history. The study participants provided information on their lifestyle and health every 2 years. The investigators excluded patients with a history of cancer, inflammatory bowel disease, or implausible caloric intake.
Among 2,811 incident colorectal cancer cases, 1,065 of the patients had tissue available for analyzing F nucleatum. The investigators revealed that those who had undergone appendectomy had a 47% lower risk of developing F nucleatum–positive colorectal cancer compared with those who hadn't undergone the procedure. There was no increase in the risk of developing colorectal cancer overall or colorectal cancer subtypes among those who underwent appendectomy.
Conclusions
The investigators plan to determine the impact of appendectomies on colorectal neoplasms containing other potentially pathogenic bacteria in future studies. They also hope to explore the appendix’s role in contributing bacteria to the gut microbiome and how its absence may influence different facets of human health.
The limitations of the study included the predominantly White, non-Hispanic identity of the patients. The investigators were only able to access information on appendectomies that had been performed by the time of the specific questionnaire and were unable to incorporate the impact of appendectomies performed after that time. However, appendectomies are most commonly performed in patients aged 15 and 30 years, and participants had a median age of 58 years and 53 years for female and male patients at the time of the specific questionnaire, respectively. Further, bacterial data were not available for all colorectal cancer cases.
“In our study, we examined the link between appendectomies and colorectal cancers positive for a specific strain of bacteria. However, many types of bacteria contribute to tumor development, and the full spectrum of bacteria the appendix harbors remains unclear. Thus, we cannot definitively say whether removing an organ considered to be a potential ‘safe house’ for certain bacteria always affects colorectal cancer risk positively or negatively, nor can we recommend removing it preventatively,” emphasized Dr. Ogino. “We understand that the appendix plays a role in immune function, and our research aims to shed more light on the appendix's role in the body and how its removal impacts our overall health in the long term,” he concluded.
The research in this study was supported by the National Institutes of Health, the Cancer Research UK Grand Challenge Award, an ASCO Conquer Cancer Foundation Career Development Award, grants from the Prevent Cancer Foundation and American Institute for Cancer Research, the Stand Up To Cancer Colorectal Cancer Dream Team Translational Research Grant, and in part by the Uehara Memorial Foundation.
Disclosure: For full disclosures of the study authors, visit journals.lww.com.
