Colorectal cancer risk following appendectomy: a pooled analysis of three large prospective cohort studies

Prior Appendicectomy and Gut Microbiota Re-Establishment in Adults after Bowel Preparation and Colonoscopy

Emerging evidence suggests that the human vermiform appendix is not a vestigial organ but rather an immunological organ of biological relevance. It is hypothesised that the appendix acts as a bacterial 'safe house' for commensal gut bacteria and facilitates re-inoculation of the colon after disruption through the release of biofilms. To date, no studies have attempted to explore this potential mechanistic function of the appendix. We conducted a pre-post intervention study in adults (n = 59) exploring re-establishment of the gut microbiota in those with and without an appendix after colonic disruption via bowel preparation and colonoscopy. Gut microbiota composition was measured one week before and one month after bowel preparation and colonoscopy using 16S rRNA sequencing. We observed between group differences in gut microbiota composition between those with (n = 45) and without (n = 13) an appendix at baseline. These differences were no longer evident one-month post-procedure, suggesting that this procedure may have 'reset' any potential appendix-related differences between groups. Both groups experienced reductions in gut microbiota richness and shifts in beta diversity post-procedure, with greater changes in those without an appendix, and there were five bacterial genera whose re-establishment post-procedure appeared to be moderated by appendicectomy status. This small experimental study provides preliminary evidence of a potential differential re-establishment of the gut microbiota after disruption in those with and without an appendix, warranting further investigation into the potential role of the appendix as a microbial safe house.

Risk of colorectal cancer and adenoma after an appendectomy: results from three large prospective cohort studies and meta-analysis

PURPOSE

The relationship between appendectomy and subsequent colorectal cancer risk remains unclear, and no study has examined its association with colorectal adenoma.

METHODS

We used data from three prospective cohorts: Health Professionals Follow-up Study, Nurses' Health Study (NHS), and NHSII. Appendectomy history was self-reported at baseline. Colorectal cancer risk was analyzed with Cox proportional hazard models among 224,109 participants followed up to 32 years. Colorectal adenoma risk was evaluated among 157,490 participants with at least one lower gastrointestinal endoscopy during follow-up with logistic regression models accounting for repeated observations. We also performed a meta-analysis of cohort studies that examined association between appendectomy and colorectal cancer risk.

RESULTS

We documented 3,384 colorectal cancers, 13,006 conventional adenomas, and 11,519 serrated polyps during the follow-up period. Compared to participants without appendectomy, those who reported appendectomy history were not at higher risk of colorectal (HR [95% CI], 0.92 [0.84-1.00]), colon (0.92 [0.83-1.01]), or rectal (0.85 [0.70-1.03]) cancer. Similarly, appendectomy history was not associated with higher risk of conventional adenoma (OR [95% CI], 1.00 [0.97-1.02]), serrated polyp (0.97 [0.94-1.00]), or high-risk adenoma (0.96 [0.92-1.01]). The meta-analysis showed appendectomy was associated with a higher risk of colorectal cancer within a short time after the procedure (1.68 [1.01-2.81]), while the long-term risk was slightly inverse (0.94 [0.90-0.97]).

CONCLUSION

We found no evidence of an association between appendectomy history and long-term risk of colorectal cancer or its precursors. The observed higher risk of colorectal cancer right after appendectomy in the first few years is likely due to reverse causation.

Appendectomy and appendicitis do not increase colorectal cancer risk: evidence from Mendelian randomization

Background

Acute appendicitis (AA) is one of the most prevalent acute abdominal diseases and appendectomy is the definitive treatment of appendicitis. However, whether appendicitis and appendectomy cause colorectal cancer (CRC) is controversial. The results of observational studies are contradictory, but randomized controlled trials (RCT) cannot be conducted.

Methods

Data of appendectomy, AA, and CRC were obtained from the IEU Open GWAS project. We selected several Genome-wide association studies (GWAS) summary statistics for CRC: statistics for colon cancer (CC) were obtained from MRC-IEU and Neale lab, respectively; statistics for rectum cancer (RC) were obtained from MRC-IEU and FinnGen, respectively; statistics for CRC were provided by Sakaue S et al. Mendelian randomization (MR) was used to evaluate the causal relationships between exposure and outcomes. Inverse variance weighting (IVW) was the most important analysis method. Meta-analysis was used to summarize the results of IVW to increase the reliability and sensitivity analysis was used to evaluate the robustness of the results.

Results

According to the results of IVW, appendectomy did not increase risk of CC: MRC-IEU (OR:1.009, 95%CI:0.984-1.035, P=0.494), Neale lab (OR:1.016, 95%CI:0.993-1.040, P=0.174); Appendectomy also did not increase risk of RC: MRC-IEU(OR:0.994, 95%CI:0.974-1.014, P=0.538), FinnGen(OR:2.791, 95%CI:0.013-580.763, P=0.706); Appendectomy also did not increase risk of CRC: Sakaue S(OR:1.382, 95%CI:0.301-6.352, P=0.678). Appendicitis did not increase risk of CC: MRC-IEU(OR:1.000, 95%CI:0.999-1.001, P=0.641), Neale lab(OR:1.000, 95%CI:1.000-1.001, P=0.319); Appendicitis also did not increase risk of RC: MRC-IEU(OR:1.000, 95%CI:0.999-1.000, P=0.361), FinnGen(OR:0.903, 95%CI:0.737-1.105, P=0.321); Appendicitis also did not increase risk of CRC: Sakaue S (OR:1.018, 95%CI:0.950-1.091, P=0.609). The results of Meta-analysis also showed appendectomy (P=0.459) and appendicitis (P=0.999) did not increase the risk of CRC.

Conclusions

Appendectomy and appendicitis do not increase the risk of colorectal cancer. More clinical trials are needed in the future to verify the causal relationships.

Beyond a vestigial organ: effects of the appendix on gut microbiome and colorectal cancer

The role of appendectomy in the pathogenesis of colorectal cancer (CRC) is a recent topic of contention. Given that appendectomy remains one of the most commonly performed operations and a first-line management strategy of acute appendicitis, it is inherently crucial to elucidate the association between prior appendectomy and subsequent development of CRC, as there may be long-term health repercussions. In this review, we summarize the data behind the relationship of CRC in post-appendectomy patients, discuss the role of the microbiome in relation to appendectomy and CRC pathogenesis, and provide an appraisal of our current understanding of the function of the appendix. We seek to piece together the current landscape surrounding the microbiome and immunological changes in the colon post-appendectomy and suggest a direction for future research involving molecular, transcriptomic, and immunologic analysis to complement our current understanding of the alterations in gut microbiome.

Epidemiological insights into colorectal cancer in northwestern Algeria

Objectives

The incidence of colorectal cancer (CRC) has exhibited regional variability in North Africa and the Middle East, with a steady increase in Algeria. Despite this trend, limited data exist on the epidemiology of CRC in northwestern Algeria. Our study aimed to investigate the epidemiological characteristics of CRC in this region.

Methods

We conducted a retrospective study examining 255 confirmed CRC cases through medical records from patients at the Sidi Bel Abbes anti-cancer centre.

Results

The mean age of the study participants was 59 ± 13 years. The results showed a higher incidence in males (57%) than in females, and colon (62%) than rectal cancer. Within this cohort, 47% had a pre-existing medical condition, while 39% had a family history of cancer. Adenocarcinomas were the prevailing histological subtype in 94% of CRC cases. Compared with colon cancer, rectal cancer was less often diagnosed at stage IV of the disease (OR = 0.75; 95% CI = 0.09, 4.86; p = 0.8) and more likely in early-onset patients (OR = 2.27; 95% CI = 1.25, 4.17; p = 0.007). Men were at a higher risk of being diagnosed with metastatic CRC primarily hepatic metastases (OR = 2.03; 95% CI = 1.07, 3.99; p = 0.033) and pulmonary metastases (OR = 2.50; 95% CI = 1.07, 6.59; p = 0.045).

Conclusion

This study may provide a comprehensive glimpse into CRC epidemiology in northwest Algeria. Understanding regional differences is the key to implementing specific preventive and interventional strategies.

The appendix and ulcerative colitis - an unsolved connection

The appendix is thought to have a role in the pathogenesis of ulcerative colitis, but the nature and basis of this association remains unclear. In this Perspective, we consider the biology of the appendix with respect to its immunological function and the microbiome, and how this relates to evidence that supports the involvement of the appendix in ulcerative colitis. In experimental models, removal of the inflamed appendix prevents colitis, and in human observational studies, appendectomy is associated with protection against ulcerative colitis. Further, among people who develop ulcerative colitis, appendectomy before diagnosis might influence the course and outcomes of the disease - some evidence suggests that it protects against colectomy but could increase the risk of colorectal cancer. Appendectomy after onset of ulcerative colitis seems to have disparate consequences. Clinical trials to understand whether appendectomy has a role in the treatment of ulcerative colitis are ongoing. Major questions about the role of the appendix in the pathogenesis of ulcerative colitis remain unanswered, and further research is needed to establish whether the connection is clinically relevant.

Risk of colorectal cancer after appendectomy: A systematic review and meta-analysis

BACKGROUND AND AIM

Appendectomy is associated with various diseases, but whether it increases the risk of colorectal cancer (CRC) remains uncertain. We conducted a systematic review and meta-analysis aimed at investigating the suggested correlation between appendectomy and CRC.

METHODS

Systematic retrieval was performed using the PubMed, Embase, Cochrane library, Web of Science, and ClinicalTrials.gov databases up to May 4, 2022, for studies reported the influence of appendectomy on CRC, colon cancer (CC) or rectal cancer (RC). Odd ratios (ORs) and 95% confidence intervals (CIs) of CRC after appendectomy were pooled using the random effects model. Subgroup analyses were carried on by region, sex, and tumor location.

RESULTS

Our search identified 1743 articles, of which 22 studies from three continents published between 1964 and 2022 were eligible for inclusion. Overall, people with appendectomy had a higher risk of CRC (OR = 1.31; 95% CI [1.05, 1.62]). But the risk for Europeans was not significant (OR = 0.94; 95% CI [0.87, 1.02]; I²  = 0%), while for Americans and Asians, appendectomy would increase the risk of CRC (OR = 1.68; 95% CI [1.15, 2.44]; I²  = 65% and OR = 1.46; 95% CI [1.04, 2.05]; I²  = 98%), especially in females and in developing countries. It is worth noting that appendectomy might be a protective factor for CC in European women (OR = 0.87; 95% CI [0.77, 0.98]; I²  = 0%).

CONCLUSIONS

Appendectomy may be a risk factor for CRC, with varying degrees in different populations. More high-quality cross-regional studies are needed for better clinical decision making.

Risk of colorectal cancer in patients with appendicitis over the age of 40 years

AIM

Acute appendicitis in late adulthood is hypothesized to be associated with an increased risk of colorectal cancer (CRC). This study aimed to establish whether patients over the age of 40 years presenting with appendicitis had an increased risk of being diagnosed with CRC over the subsequent 3 years.

METHOD

This is a retrospective review of patients aged 40 years and over presenting to Canterbury District Health Board with appendicitis from January 2010 to December 2015. Clinical details were obtained for these patients and cross-referenced with the New Zealand Cancer Registry for the 3 years following diagnosis. The incidence ratio rate (IRR) and standardized incidence ratio (SIR) were calculated by establishing the incidence of CRC in this cohort and comparing it with the Canterbury population data.

RESULTS

A total of 1099 patients met the inclusion criteria. The majority (75%) underwent CT as part of their initial work-up. The rate of colonoscopy increased with age from around 10% between 40 and 49 years to 27% for those 70 years and over. Eleven cases of CRC were identified, resulting in an IRR 2.35 (95% CI 1.17-4.21). The SIR for this population was 3.28 (95% CI 1.82-5.92).

CONCLUSION

The rate of CRC is significantly increased compared with the background population in this cohort. The results of this study support luminal investigation of adults aged 40 years and over who present with acute appendicitis as CT alone was insufficient to detect the pathology.

Construction and assessment of a joint prediction model and nomogram for colorectal cancer

BACKGROUND

Colorectal cancer (CRC) is one of the most common tumors in the digestive system, and all its risk factors are not yet known. It is important to identify valuable clinical indicators to predict the risk of CRC.

METHODS

A total of 227 participants, comprising 162 healthy adults and 65 patients diagnosed with CRC at Tianjin Hospital from January 2017 to March 2022, were included in this study. Electrochemiluminescence was adopted to test the expression levels of carcinoembryonic antigen (CEA), carbohydrate antigen 19-9 (CA199). Univariate and multivariate logistic regression analyses were performed to identify independent risk factors for CRC, and a joint prediction model was then constructed. A nomogram was prepared, and the model was later assessed using the receiver operating characteristic curve and calibration curve.

RESULTS

The univariate analysis showed that there were statistically significant differences between the two groups in terms of smoking (χ²=8.67), fecal occult blood (χ²=119.41), Helicobacter pylori (H. pylori) infection (χ²=30.87), a history of appendectomy (χ²=5.47), serum total bile acid levels (t=19.80), serum CEA levels (t=37.82), serum CA199 levels (t=6.82), and serum ferritin levels (t=54.31) (all P<0.05). The multiple logistic regression analysis showed that smoking, fecal occult blood, H. pylori infection, a history of appendectomy, serum CEA levels, and serum CA199 levels were independent risk factors for CRC (all P<0.05). Based on the above findings, a joint prediction model was constructed, and the area under the receiver operator characteristic (ROC) curve of the model was 0.842. A nomogram and calibration curve was drawn, and the internal validation results indicated that the model had good diagnostic value.

CONCLUSIONS

Smoking, fecal occult blood, H. pylori infection, a history of appendectomy, serum CEA levels, and serum CA199 levels are independent risk factors for CRC, and the prediction model based on these factors had good predictive ability.