Cholecystectomy and the risk of colon cancer

Metabolic Rewiring in Cancer: Small Molecule Inhibitors in Colorectal Cancer Therapy

Alterations in cellular metabolism, such as dysregulation in glycolysis, lipid metabolism, and glutaminolysis in response to hypoxic and low-nutrient conditions within the tumor microenvironment, are well-recognized hallmarks of cancer. Therefore, understanding the interplay between aerobic glycolysis, lipid metabolism, and glutaminolysis is crucial for developing effective metabolism-based therapies for cancer, particularly in the context of colorectal cancer (CRC). In this regard, the present review explores the complex field of metabolic reprogramming in tumorigenesis and progression, providing insights into the current landscape of small molecule inhibitors targeting tumorigenic metabolic pathways and their implications for CRC treatment.

Increased Risk of Cancer after Cholecystectomy: A Nationwide Cohort Study in Korea including 123,295 Patients

Background/Aims

Contradictory findings on the association between cholecystectomy and cancer have been reported. We aimed to investigate the risk of all types of cancers or site-specific cancers in patients who underwent cholecystectomy using a nationwide dataset.

Methods

Subjects who underwent cholecystectomy from January 1, 2007, to December 31, 2014, who were older than 20 years and who underwent an initial baseline health check-up within 2 years were enrolled. Those who were diagnosed with any type of cancer before the enrollment or within 1 year after enrollment were excluded. Ultimately, patients (n=123,295) who underwent cholecystectomy and age/sex matched population (n=123,295) were identified from the database of the Korean National Health Insurance Service. The hazard ratio (HR) and 95% confidence interval (CI) for cancer were estimated, and Cox regression analysis was performed.

Results

The incidence of cancer in the cholecystectomy group was 9.56 per 1,000 personyears and that in the control group was 7.95 per 1,000 person-years. Patients who underwent cholecystectomy showed an increased risk of total cancer (adjusted HR, 1.19; 95% CI, 1.15 to 1.24; p<0.001), particularly leukemia and malignancies of the colon, liver, pancreas, biliary tract, thyroid, pharynx, and oral cavity. In the subgroup analysis according to sex, the risk of developing cancers in the pancreas, biliary tract, thyroid, lungs and stomach was higher in men than in women.

Conclusions

Physicians should pay more attention to the possibility of the occurrence of secondary cancers among patients who undergo cholecystectomy.

Emerging Therapeutic Agents for Colorectal Cancer

There are promising new therapeutic agents for CRC patients, including novel small-molecule inhibitors and immune checkpoint blockers. We focused on emerging CRC’s therapeutic agents that have shown the potential for progress in clinical practice. This review provides an overview of tyrosine kinase inhibitors targeting VEGF and KIT, BRAF and MEK inhibitors, TLR9 agonist, STAT3 inhibitors, and immune checkpoint blockers (PD1/PDL-1 inhibitors), for which recent advances have been reported. These new agents have the potential to provide benefits to CRC patients with unmet medical needs.

Prevalence and Risk Factors of Gastric and Colorectal Cancer after Cholecystectomy

BACKGROUND

Previous studies on the relationship between gastrointestinal (GI) cancer and cholecystectomy remain inconclusive. We aimed to evaluate this relationship, albeit particularly between cholecystectomy and gastric cancer or colorectal cancer (CRC), and the risk factors of cancer among individuals who have undergone cholecystectomy in Korea.

METHODS

In total, 4,222 patients who underwent laparoscopic or open cholecystectomy at our institution between January 2006 and December 2013 were included. Patients who underwent cholecystectomy for gallbladder cancer or were undergoing surgery for GI, hepatic, or pancreatobiliary cancers were excluded, as were those who developed stomach cancer or CRC within a year of their cholecystectomy. The included patients were followed until July 20, 2020. The standardized incidence ratio (SIR) was used to calculate the relative risk of GI cancer in cholecystectomy patients.

RESULTS

The median patient age (n = 3,588) at the time of cholecystectomy was 54.0 (range, 19-95) years, and the male-to-female ratio was 1:1.04. The median follow-up period after cholecystectomy was 15.0 (range, 0-146) months. We found a 108% greater risk of CRC (SIR, 2.08; 95% confidence interval [CI], 1.28-3.17) and 154% increased risk of CRC in females (SIR, 2.54; 95% CI, 1.16-4.84). Based on multivariate analysis, an age of > 60 years was a significant risk factor for GI cancer in cholecystectomy patients.

CONCLUSION

Cholecystectomy may increase risk of CRC, especially in females. Age was considered a risk factor of GI cancers in patients with history of cholecystectomy.

The risk of developing a mismatch repair deficient colorectal cancer after undergoing cholecystectomy

OBJECTIVES

Mismatch repair deficient (dMMR) colorectal cancer (CRC) is caused by inactivation of the MMR DNA repair system, most commonly via epigenetic inactivation of the MLH1 gene, and these tumors occur most frequently in the right colon. The objective was to determine whether cholecystectomy (CCY) increases the risk of a dMMR CRC by comparing CCY incidence in patients with dMMR CRC and proficient MMR (pMMR) CRC to unaffected controls.

MATERIALS AND METHODS

All patients diagnosed with CRC in Iceland from 2000 to 2009 (n = 1171) were included. They had previously been screened for dMMR by immunohistochemistry (n = 129 were dMMR). Unaffected age- and sex-matched controls (n = 17,460) were obtained from large Icelandic cohort studies. Subjects were cross-referenced with all pathology databases in Iceland to establish who had undergone CCY. Odds ratios were calculated using unconditional logistic regression.

RESULTS

Eighteen (13.7%) dMMR CRC cases and 90 (8.7%) pMMR CRC cases had undergone CCY compared to 1532 (8.8%) controls. CCY-related odds ratios (OR) were 1.06 (95% CI 0.90-1.26, p = .577) for all CRC, 1.16 (95% CI 0.66-2.05 p = .602) for dMMR CRCand 1.04 (95% CI 0.83-1.29, p = .744) for pMMR CRC. Furthermore, OR for dMMR CRC was 0.51 (95% CI 0.16-1.67, p = .266), 2.04 (95% CI 0.92-4.50, p = .080) and 1.08 (95% CI 0.40-2.89, p = .875) <10 years, 10-20 years and >20 years after a CCY, respectively.

CONCLUSIONS

There was no evidence of increased risk of developing dMMR CRC after CCY although a borderline significantly increased 2-fold risk was observed 10-20 years after CCY. Larger studies are warranted to examine this further.

Functions of the Gallbladder

The gallbladder stores and concentrates bile between meals. Gallbladder motor function is regulated by bile acids via the membrane bile acid receptor, TGR5, and by neurohormonal signals linked to digestion, for example, cholecystokinin and FGF15/19 intestinal hormones, which trigger gallbladder emptying and refilling, respectively. The cycle of gallbladder filling and emptying controls the flow of bile into the intestine and thereby the enterohepatic circulation of bile acids. The gallbladder also largely contributes to the regulation of bile composition by unique absorptive and secretory capacities. The gallbladder epithelium secretes bicarbonate and mucins, which both provide cytoprotection against bile acids. The reversal of fluid transport from absorption to secretion occurs together with bicarbonate secretion after feeding, predominantly in response to an adenosine 3',5'-cyclic monophosphate (cAMP)-dependent pathway triggered by neurohormonal factors, such as vasoactive intestinal peptide. Mucin secretion in the gallbladder is stimulated predominantly by calcium-dependent pathways that are activated by ATP present in bile, and bile acids. The gallbladder epithelium has the capacity to absorb cholesterol and provides a cholecystohepatic shunt pathway for bile acids. Changes in gallbladder motor function not only can contribute to gallstone disease, but also subserve protective functions in multiple pathological settings through the sequestration of bile acids and changes in the bile acid composition. Cholecystectomy increases the enterohepatic recirculation rates of bile acids leading to metabolic effects and an increased risk of nonalcoholic fatty liver disease, cirrhosis, and small-intestine carcinoid, independently of cholelithiasis. Among subjects with gallstones, cholecystectomy remains a priority in those at risk of gallbladder cancer, while others could benefit from gallbladder-preserving strategies. © 2016 American Physiological Society. Compr Physiol 6:1549-1577, 2016.

Cholecystectomy and the risk of alimentary tract cancers: A systematic review

AIM: To investigate the association between cholecystectomy and gastro-intestinal tract (GIT) cancers.

METHODS: We conducted a systematic review according to the PRISMA guidelines. A MEDLINE search was performed with predefined search criteria for English Language articles on the association between cholecystectomy and GIT cancers. Additional articles were retrieved by manual search of references. All relevant articles were accessed in full text. Data on study type; cases; controls; country; effect estimate; adjustments for confounders and quality of publication were extracted. The quality of the publications were scored by adherence to the STROBE checklist. The data for each part of the GIT were presented in separate tables.

RESULTS: Seventy-five studies and 5 meta-analyses satisfied the predefined criteria for inclusion and were included in this review. There were inconsistent reports and no strong evidence of an association between cholecystectomy and cancers of the oesophagus (Adenocarcinoma), pancreas, small bowel and right-sided colon cancers. In squamous cancer of the oesophagus, cancers of the stomach, liver, bile ducts, small bowel and left sided colon cancers, good quality studies suggested a lack of association with cholecystectomy. Equally, distal colon and rectal cancers were found not to be associated with cholecystectomy. Several mechanisms for carcinogenesis/promotion of carcinogensis have been proposed. These have focused on a role for bile salts in carcinogenesis with several potential mutagenic molecular events and gut metabolic hormones signaling cell proliferation or initiation of carcinogenesis.

CONCLUSION: This is a comprehensive review of the association between GIT cancers and cholecystectomy. This review found no clear association between cholecystectomy and GIT cancers.

Gallstones, cholecystectomy, and risk of digestive system cancers

Gallstones and cholecystectomy may be related to digestive system cancer through inflammation, altered bile flux, and changes in metabolic hormone levels. Although gallstones are recognized causes of gallbladder cancer, associations with other cancers of the digestive system are poorly established. We used the Surveillance, Epidemiology, and End Results (SEER)-Medicare linked database (1992-2005), which includes 17 cancer registries that cover approximately 26% of the US population, to identify first primary cancers (n = 236,850) occurring in persons aged ≥66 years and 100,000 cancer-free population-based controls frequency-matched by calendar year, age, and gender. Odds ratios and 95% confidence intervals were calculated using logistic regression analysis, adjusting for the matching factors. Gallstones and cholecystectomy were associated with increased risk of noncardia gastric cancer (odds ratio (OR) = 1.21 (95% confidence interval (CI): 1.11, 1.32) and OR = 1.26 (95% CI: 1.13, 1.40), respectively), small-intestine carcinoid (OR = 1.27 (95% CI: 1.01, 1.60) and OR = 1.78 (95% CI: 1.41, 2.25)), liver cancer (OR = 2.35 (95% CI: 2.18, 2.54) and OR = 1.26 (95% CI: 1.12, 1.41)), and pancreatic cancer (OR = 1.24 (95% CI: 1.16, 1.31) and OR = 1.23 (95% CI: 1.15, 1.33)). Colorectal cancer risk associated with gallstones and cholecystectomy decreased with increasing distance from the common bile duct (P-trend < 0.001). Hence, gallstones and cholecystectomy are associated with the risk of cancers occurring throughout the digestive tract.

Cholangitis and subsequent gastrointestinal cancer risk: a Danish population-based cohort study

OBJECTIVE

While patients with gastrointestinal cancer are at increased risk of cholangitis, it is less clear whether cholangitis is also a marker for occult gastrointestinal cancer. If an undiagnosed cancer obstructs the bile duct system and causes cholangitis, the short-term risk of cancer will appear increased. However, an increased long-term risk of cancer may originate from chronic inflammatory processes. We assessed the risk of a gastrointestinal cancer diagnosis subsequent to a cholangitis diagnosis during a 17-year period in Denmark.

DESIGN

We conducted a nationwide population-based cohort study by linking Danish medical registries during 1994-2010. We quantified the excess risk of cancer in cholangitis patients using relative (standardised incidence ratio; SIR) and absolute (excess absolute risk per 1000 person-years at risk; EAR) risk calculations.

RESULTS

4333 patients with cholangitis (including 178 with primary sclerosing cholangitis) were followed for 17 222 person-years. During the follow-up period, 477 gastrointestinal cancers occurred versus 59 expected, corresponding to a SIR of 8.12 (95% CI 7.41 to 8.88). Risk was increased mainly for cancer in the small intestine (SIR 18.2; 95% CI 8.69 to 33.4), liver (SIR 16.3; 95% CI 11.6 to 22.2), gallbladder and biliary tract (SIR 70.9; 95% CI 59.0 to 84.4) and pancreas (SIR 31.7; 95% CI 27.8 to 36.0). During the first 6 months of follow-up, 314 patients were diagnosed with gastrointestinal cancer, corresponding to a SIR of 49.8 (95% CI 44.4 to 55.6) and an EAR of 175.

CONCLUSIONS

Cholangitis is a marker of occult gastrointestinal cancer.

Gallstone disease is associated with rectal cancer: a meta-analysis

BACKGROUND

Increased levels of secondary bile acids after cholecystectomy and cholelithiasis are believed to increase the risk of colorectal cancer, and several studies have suggested that the risk of colorectal cancer may be the greatest proximally. Numerous conflicting studies have been published and it remains unclear whether the risk is apparent in the rectum. This meta-analysis aims to determine the risk of developing rectal cancer following gallstone disease or cholecystectomy.

METHODS

The prospective protocol included a literature search of PubMed, MEDLINE, EMBASE, and Current Contents (1950-2011). Selection criteria were developed to sort for studies exploring the relationship between cholelithiasis, cholecystectomy, and rectal cancer in an adult population. A random-effects model was used to generate pooled odds ratios (OR) and 95% confidence intervals (CI). Publication bias and heterogeneity were assessed.

RESULTS

Of the 2358 studies identified, 42 were suitable for final analysis. There were 1,547,506 subjects in total, 14,226 diagnosed with rectal cancer, and 496,552 with gallstones or cholecystectomy. There was a statistically significant risk of rectal cancer following cholelithiasis (OR = 1.33; 95% CI = 1.02-1.73), though no risk was apparent following cholecystectomy (OR = 1.14; 95% CI = 0.92-1.41).

CONCLUSIONS

Cholelithiasis increases the risk of rectal cancer. No association exists between cholecystectomy and rectal cancer.

Meta-analysis of observational studies on cholecystectomy and the risk of colorectal adenoma

AIM

Cholecystectomy has been suggested as a risk factor for colorectal cancer. However, the association of cholecystectomy and the risk of colorectal adenoma (CRA) remains unclear. We conducted a meta-analysis of observational studies to explore this relationship.

METHODS

We identified studies by a literature search of MEDLINE and EMBASE through 30 September 2011, and by searching the reference lists of pertinent articles. Summary relative risks (SRRs) with their 95% confidence intervals (CIs) were calculated with a random-effects model. Between-study heterogeneity was assessed using Cochran's Q statistic and the I2.

RESULTS

A total of 10 studies (including 4061 CRA cases) were included in this meta-analysis. Analysis of these 10 studies found that no effect of cholecystectomy on the risk of CRAs was shown (SRR, 1.17; 95% CI: 0.93-1.48), with no significant heterogeneity among these studies (P heterogeneity=0.106, I2=37.9%). This null association was seen in both men and women (men: SRR=1.00, 95% CI: 0.58-1.73; women: SRR=1.39, 95% CI: 0.95-2.04).

CONCLUSION

The results of this meta-analysis suggest that there is no positive association between previous cholecystectomy and the risk of CRA development in both men and women.

Acquired risk factors for colorectal cancer

The risk of developing colorectal cancer (CRC) is influenced by several acquired risk factors, including environmental exposures and comorbid medical conditions that are partially genetic in nature. These risk factors are based on data almost exclusively derived from observational studies. Because of the possibility of bias due to confounding, these acquired risk factors should not be automatically assumed to be causative, and in fact some may not be truly independent risk factors. Acquired risk factors include the following categories: 1) dietary factors, 2) lifestyle factors, 3) side-effects of medical interventions, and 4) comorbid medical conditions. Dietary factors that potentially increase the risk of CRC include low fruit, vegetable, or fiber intake, high red meat or saturated fat consumption, and exposure to caffeine or alcohol. Of these factors, the significance of low fruit, vegetable, and fiber intake has been called into question because of contradictory results from large observational studies and negative results from randomized trials. The association of high red meat or saturated fat consumption with increased CRC risk is supported by the preponderance of observational data. Lifestyle factors include lack of exercise and smoking. These risk factors are supported by observational data of moderate quality. Medical interventions that may increase the risk of CRC include pelvic irradiation, cholecystectomy, and ureterocolic anastomosis after major surgery of the urinary and intestinal tracts. Aside from cholecystectomy, these risk factors are supported by observational data from small studies only, therefore their validity is not well established. Finally, comorbid medical conditions that are associated with increased risk of CRC include Barrett's esophagus, human immunodeficiency virus infection, acromegaly, and inflammatory bowel disease. The association between inflammatory bowel disease and CRC is well established and it forms the basis for widely adopted colonoscopic surveillance recommendations from national medical organizations. The other factors are supported by limited observational data only and are still controversial.

Proximalisation of colorectal carcinoma: a 10-year study in Italy

INTRODUCTION

Proximalisation of colon carcinoma has been reported over the course of the last 60 years. Changes in site distribution are receiving increasing attention on account of their implications for screening programmes.

OBJECTIVE

A retrospective observational study to determine whether the site distribution of colorectal carcinoma in Italy has varied in the last years and whether changes have been influenced by age and sex.

METHODS

Findings of colonscopies conducted at Turin University from 1992 to 2001 were examined. Inclusion criteria were: outpatients, screening, presence of anaemia or gastrointestinal bleeding, weight loss, constipation or changes in evacuation frequency. Exclusion criteria were: uncompleted, surgical endoscopies or conducted for positive flexible sigmoidoscopy, with doubtful findings. Carcinomas and benign polyps were diagnosed histologically. Age, sex, date of examination, nature and location of lesions were recorded. Lesions were classed as carcinoma, and polyps <1 and >/=1 cm. Data were grouped into different year periods and compared with the chi square test. We compared 1992-1993 vs. 2000-2001 and 1992-1996 vs. 1997-2001.

RESULTS

Of the 8,132 colonoscopies performed, 7,342 were included in the study. Proximal carcinomas moved from 12.2% in 1992-1993 to 14.9% in 2000-2001 (P = 0.57), proximal polyps rose from 16.6% to 22.1% (P < 0.0001). Furthermore proximal carcinomas moved from 16.5% in 1992-1996 to 14.4% in 1997-2001 (P = 0.48); proximal polyps rose from 18.4% to 27.8% (P < 0.005). In the period 1996-2001 there was higher female prevalence (P = 0.0011) and older age (P = 0.0191).

DISCUSSION

We can suppose that proximalisation of carcinoma has not yet appeared in Italy.

Cholecystectomy and the risk of colorectal adenomas

Cholecystectomy has been identified as a risk factor for colorectal cancer, yet little attention has been given to the relationship between cholecystectomy and colorectal adenomas. Utilizing data collected in two large cross-sectional studies of colorectal adenoma risk factors, we examined the association between cholecystectomy and colorectal adenomas. In the adjusted logistic regression model, both men and women showed no effect of cholecystectomy on risk of colorectal adenomas (men: OR 0.67 [95% CI 0.30-1.47]; women: OR 1.46 [95% CI 0.92-2.29]). No effect was seen when examining the time since cholecystectomy for men. There was a slight association found for women who had a cholecystectomy less than 10 years prior (OR 2.02 [95% CI 1.06-3.87]) but no association was seen in women with cholecystectomy at least 10 years prior (OR 1.14 [95% CI 0.62-2.09]). Thus, we conclude that, although cholecystectomy is a risk factor for colorectal cancer, cholecystectomy is not a risk factor for colorectal adenomas.

The comparison of the risk factors and clinical manifestations of proximal and distal colorectal cancer

PURPOSE

Colorectal cancers in the proximal or distal site have distinct clinical characteristics. In this study, the authors compared the risk factors of proximal and distal colorectal cancer.

METHODS

A 16-page questionnaire was administered to 529 patients with colorectal cancer before operation. Cancers were classified as proximal or distal relative to the splenic flexure. Of these 529 patients, 6 patients were excluded because of the presence of synchronous colorectal cancers. Data of the 523 patients were analyzed.

RESULTS

Total numbers of proximal and distal cancers were 123 and 400. The proportion of patients with Type 2 diabetes was significantly higher for distal cancer (P = 0.034), whereas a greater proportion of patients with proximal cancer had a gallstone history (P = 0.005). Multivariate analysis revealed Type 2 diabetes to be a risk factor for distal colorectal cancer (P = 0.027) and cholelithiasis to be a risk factor for proximal cancer (P = 0.049). The odds ratio for distal colorectal cancer among males with Type 2 diabetes was 4.1 (95 percent confidence interval, 1.4-12.1). On the other hand, a gallstone history was more associated with proximal colon cancer, especially in females (odds ratio = 5.5; 95 percent confidence interval, 1.4-20.9).

CONCLUSIONS

A comparison of the risk factors of proximal and distal colorectal cancer showed that Type 2 diabetes is associated with distal colorectal cancer in males and that cholelithiasis is associated with proximal colon cancer in females.

DNA Methylation Profiles of Female Steroid Hormone-Driven Human Malignancies

Tumor DNA contains valuable clues about the origin and pathogenesis of human cancers. Alterations in DNA methylation can lead to silencing of genes associated with distinct tumorigenic pathways. These pathway-specific DNA methylation changes help define tumor-specific DNA methylation profiles that can be used to further our understanding of tumor development, as well as provide tools for molecular diagnosis and early detection of cancer. Female sex hormones have been implicated in the etiology of several of the women's cancers including breast, endometrial, ovarian, and proximal colon cancers. We have reviewed the DNA methylation profiles of these cancers to determine whether the hormonal regulation of these cancers results in specific DNA methylation alterations. Although subsets of tumors in each of these four types of cancers were found to share some DNA methylation alterations, we did not find evidence for global hormone-specific DNA methylation alterations, suggesting that female sex hormones may participate in different tumorigenic pathways that are associated with distinct DNA methylation-based molecular signatures. One such pathway may include MLH1 methylation in the context of the CpG island methylator phenotype.

Colorectal Cancer: Epidemiology and Health Services Research

The causes of colorectal carcinoma are multifactorial. Numerous lines of epidemiologic evidence support the role of dietary factors, with strong associations revealed for folate and calcium, more equivocal evidence exists for dietary antioxidants. Lifestyle factors such as physical activity, alcohol in-take, and tobacco use are also positively correlated with the risk of colorectal carcinoma. Health services research examines epidemiologic issues,clinical evidence regarding prevention and treatment, patient preferences,and other factors with the goal of improving the quality of care. Observations based on epidemiologic studies and health services research will in the future provide the basis for reducing personal and social burdens caused by colorectal carcinoma.

Subsite-Specific Colorectal Cancer Incidence Rates and Stage Distributions among Asians and Pacific Islanders in the United States, 1995 to 1999

Objective: This study examined subsite-specific colorectal cancer incidence rates and stage distributions for Asians and Pacific Islanders (API) and compared the API data with data for Whites and African Americans. Methods: Data included 336,798 invasive colorectal cancer incident cases for 1995 to 1999 from 23 population-based central cancer registries, representing about two thirds of API population in the United States. Age-adjusted rates, using the 2000 U.S. standard population, and age-specific rates and stage distributions were computed by anatomic subsite, race, and gender. All rates were expressed per 100,000. SEs and rate ratios were calculated for rate comparison. A significance level of 0.05 was used for all analyses. Results: Overall, age-adjusted colorectal cancer incidence rates were significantly lower in API than in Whites and African Americans across anatomic subsites, particularly for proximal colon cancer in which rates were 40% to 50% lower in API males and females. Exception to this pattern was the significantly (10%) higher rectal cancer incidence rate in API males than in African American males. The incidence patterns by anatomic subsite within API differed from those of Whites and African Americans. Among API, the rate of rectal cancer (19.2 per 100,000) was significantly higher than the rates of proximal (15.2 per 100,000) and distal (17.7 per 100,000) colon cancers in males, with little variations in rates across anatomic subsites in females. In contrast, among White and African American males and females, proximal colon cancer rates were over 25% higher than the rates of distal colon and rectal cancers. Increases in age-specific rates with advancing age were more striking for proximal colon cancer than for distal colon and rectal cancers in Whites and African Americans, while age-specific rates were very similar for different subsites in API with parallel increases with advancing age, especially in API males. Similar to Whites and African Americans, in API, proximal colon cancers (32% to 35%) were also less likely to be diagnosed with localized stage compared with distal colon (38% to 42%) and rectal (44% to 52%) cancers. Conclusion: The patterns of subsite-specific colorectal cancer incidence in API, especially API males, differ from those of Whites and African Americans. Similar to Whites and African Americans, lower percentage of localized disease in API for proximal colon cancer than for distal colon and rectal cancers was also observed.

Epidemiology and prevention of colorectal cancer

CRC, the second-leading cause of cancer death in the United States, is a highly preventable disease. Ironically, available and effective screening technologies are not consistently applied, even as new ones are developed. This discordance between preventive opportunity and practice conveys a sobering message regarding nontechnologic issues that must be addressed if the promise of CRC prevention is to be realized. Our response to this message will determine the public health impact of cancer prevention. In the 1980s, cancer chemoprevention was regarded as scientific speculation. Within the last decade, however, cancer has been recognized as a late, nonobligate stage of carcinogenesis, a chronic process that provides time and targets for preventive intervention. Further advances are emerging out of rigorous clinical testing, which remains the limiting factor in transforming ingenious concepts into useful tools for the prevention of CRC. The challenges and rewards of participation in chemoprevention research--both as patients and health care providers-have never been greater.

Distal bowel selectivity in the chemoprevention of experimental colon carcinogenesis by the non-steroidal anti-inflammatory drug nabumetone

Use of non-steroidal anti-inflammatory drugs (NSAIDs) for chemoprevention of colon cancer has been hindered by their potential gastro-intestinal toxicity. Nabumetone, which is approximately 10 to 36 times safer than conventional NSAIDs, was evaluated in 2 models of experimental colon carcinogenesis. In azoxymethane (AOM)-treated Fisher 344 rats, nabumetone caused dose-dependent inhibition of aberrant crypt foci (ACF), with 750 and 1,500 ppm resulting in 15% and 37% reductions, respectively (p < 0.05). Moreover, complex ACF were reduced by 48% in the latter group. MIN mice studies confirmed the chemopreventive efficacy of nabumetone, with 900 ppm suppressing approximately half of the intestinal tumors. Interestingly, inhibition of intermediate biomarkers in both models was markedly greater in the distal than the proximal bowel. To mechanistically evaluate this regional selectivity, we assessed cyclo-oxygenase-2 (COX-2) expression in the uninvolved mucosa and demonstrated a 3- to 4-fold excess in the distal relative to the proximal bowel in both MIN mice and AOM-treated rats. We then investigated another putative NSAID target, peroxisome proliferator-activated receptor-delta (PPAR-delta) and demonstrated up-regulation during AOM-induced colonic tumorigenesis. Furthermore, in pre-neoplastic mucosa, there was a 3-fold excess of PPAR-delta in the distal colon. We demonstrate that nabumetone is an effective protective agent in both experimental models of colon carcinogenesis. The striking distal predilection of nabumetone may be, at least partially, explained by distal bowel over-expression of COX-2 and PPAR-delta.