Chemoprevention of colorectal cancer by aspirin: a cost-effectiveness analysis

The Association Between Aspirin and Basal Cell Carcinoma: A Clinical and Financial Analysis

Background

Nonmelanoma skin cancer (NMSC) is the most common malignancy. Basal cell carcinoma (BCC) comprises about 80% of all NMSCs and its incidence continues to rise. Although BCC rarely leads to metastases or increased mortality, its effects on healthcare costs and quality of life are substantial. Aspirin may prevent the development of basal cell carcinoma (BCC) by the inhibition of cyclooxygenase (COX) enzymes, which are associated with carcinogenesis and inflammation. This study therefore examined the effect of aspirin on the risk of BCC, its clinical outcomes, and its treatment costs.

Methods

A retrospective study (2010 - 2018) was conducted using the Humana Health Insurance Database. International Classification of Disease ninth and 10th codes and National Drug Codes were used to identify BCC diagnoses and aspirin prescriptions. Patients were matched for age, sex, Charlson Comorbidity Score (CCI), and region of residence. Chi-squared, logistic regression, and odds ratio (OR) analyses were utilized to test for significance and to estimate relative risk.

Results

Aspirin use was associated with a decreased incidence of BCC in unmatched (OR = 0.658, 95% confidence interval (CI) 0.526 - 0.820) and matched (OR = 0.54, 95% CI 0.47 - 0.61) analyses. Aspirin was also associated with a decreased BCC risk when stratified by hypertension (P = 3.888 × 10^-5), chronic obstructive pulmonary disease (COPD) (P = 0.014), diabetes (P = 0.049) and tobacco use (P = 0.017). Aspirin use was not associated with risk of BCC when stratified by obesity (P = 0.408). The average paid per patient for BCC treatment was significantly higher for patients in the aspirin use group than in the aspirin nonuse group (P = 0.0087).

Conclusions

While the high incidence and cost of treatment of BCC are demanding both clinically and financially, the low cost of aspirin and its widespread use may have vital implications for its preventative role in this disease. This study concluded that aspirin use was associated with a significantly decreased risk of BCC.

Can Cost-effectiveness Analysis Inform Genotype-Guided Aspirin Use for Primary Colorectal Cancer Prevention?

BACKGROUND

Inherited genetic variants can modify the cancer-chemopreventive effect of aspirin. We evaluated the clinical and economic value of genotype-guided aspirin use for colorectal cancer chemoprevention in average-risk individuals.

METHODS

A decision analytical model compared genotype-guided aspirin use versus no genetic testing, no aspirin. The model simulated 100,000 adults ≥50 years of age with average colorectal cancer and cardiovascular disease risk. Low-dose aspirin daily starting at age 50 years was recommended only for those with a genetic test result indicating a greater reduction in colorectal cancer risk with aspirin use. The primary outcomes were quality-adjusted life-years (QALY), costs, and incremental cost-effectiveness ratio (ICER).

RESULTS

The mean cost of using genotype-guided aspirin was $187,109 with 19.922 mean QALYs compared with $186,464 with 19.912 QALYs for no genetic testing, no aspirin. Genotype-guided aspirin yielded an ICER of $66,243 per QALY gained, and was cost-effective in 58% of simulations at the $100,000 willingness-to-pay threshold. Genotype-guided aspirin was associated with 1,461 fewer polyps developed, 510 fewer colorectal cancer cases, and 181 fewer colorectal cancer-related deaths. This strategy prevented 1,078 myocardial infarctions with 1,430 gastrointestinal bleeding events, and 323 intracranial hemorrhage cases compared with no genetic testing, no aspirin.

CONCLUSIONS

Genotype-guided aspirin use for colorectal cancer chemoprevention may offer a cost-effective approach for the future management of average-risk individuals.

IMPACT

A genotype-guided aspirin strategy may prevent colorectal cancer, colorectal cancer-related deaths, and myocardial infarctions, while minimizing bleeding adverse events. This model establishes a framework for genetically-guided aspirin use for targeted chemoprevention of colorectal cancer with application toward commercial testing in this population.

Cost-effectiveness of aspirin adjuvant therapy in early stage colorectal cancer in older patients

BACKGROUND & AIMS

Recent observational studies showed that post-operative aspirin use reduces cancer relapse and death in the earliest stages of colorectal cancer. We sought to evaluate the cost-effectiveness of aspirin as an adjuvant therapy in Stage I and II colorectal cancer patients aged 65 years and older.

METHODS

Two five-state Markov models were constructed separately for Stage I and II colorectal cancer using TreeAge Pro 2014. Two hypothetical cohorts of 10,000 individuals at a starting age of 65 years and with colorectal cancer in remission were put through the models separately. Cost-effectiveness of aspirin was evaluated against no treatment (Stage I and II) and capecitabine (Stage II) over a 20-year period from the United States societal perspective. Extensive one-way sensitivity analyses and multivariable Probabilistic Sensitivity Analyses (PSA) were performed.

RESULTS

In the base case analyses, aspirin was cheaper and more effective compared to other comparators in both stages. Sensitivity analyses showed that no treatment and capecitabine (Stage II only) can be cost-effective alternatives if the utility of taking aspirin is below 0.909, aspirin's annual fatal adverse event probability exceeds 0.57%, aspirin's relative risk of disease progression is 0.997 or more, or when capecitabine's relative risk of disease progression is less than 0.228. Probabilistic Sensitivity Analyses (PSA) further showed that aspirin could be cost-effective 50% to 80% of the time when the willingness-to-pay threshold was varied from USD 20,000 to USD 100,000.

CONCLUSION

Even with a modest treatment benefit, aspirin is likely to be cost-effective in Stage I and II colorectal cancer, thus suggesting a potential unique role in secondary prevention in this group of patients.

Clinical end points for developing pharmaceuticals to manage patients with a sporadic or genetic risk of colorectal cancer

To reduce the morbidity and mortality from colorectal cancer (CRC), current clinical practice focuses on screening for early detection and polypectomy as a form of secondary prevention, complemented with surgical interventions when appropriate. No pharmaceutical agent is currently approved for use in clinical practice for the management of patients at risk for CRC. This article will review earlier attempts to develop pharmaceuticals for use in managing patients with a sporadic or genetic risk of CRC. It will also discuss therapeutic end points under evaluation in current efforts to develop drugs for treating CRC risk factors.

The role of low-dose aspirin in the prevention of colorectal cancer

INTRODUCTION

Colorectal cancer (CRC) is a prevalent disease that is associated with considerable morbidity and mortality. The progression of normal mucosa through adenomatous polyps to overt cancer can span for 10 - 15 years, making early detection, as well as the use of chemopreventive agents such as aspirin, an attractive option. The effects of aspirin in reducing CRC incidence and mortality have consistently been demonstrated in a number of studies. However, a greater understanding of how aspirin exerts its anti-cancer effects is warranted.

AREAS COVERED

The aim of this non-systematic review, which was developed using published randomized and epidemiological studies, as well as key references known to the authors, was to consider the role of aspirin in CRC prevention. Areas covered include the effects of aspirin on cardiovascular disease, CRC and colorectal adenoma (CRA) prevention, mode of action of aspirin and the benefit-to-risk of aspirin in disease prevention.

EXPERT OPINION

Incorporating CRC and CRA benefits into coronary heart disease (CHD) risk scores would be particularly useful for determining the benefit-to-risk ratio for aspirin use in borderline cases. For instance, patients with an annual CHD risk around 0.7 - 1.4%, but with a high risk of colorectal neoplasm may benefit from aspirin. The strong association between CRC and age may also be useful for re-examining the benefit-to-risk ratio for aspirin use in older patients. However, it has to be noted that a cancer prevention indication for aspirin is not approved regulatory-wise anywhere.

Ornithine decarboxylase G316A genotype and colorectal cancer risk

AIM

Ornithine decarboxylase (ODC) is a modifier of adenomatous polyposis coli-dependent tumourigenesis. The G316 > A polymorphism in intron 1 of the ODC gene lies between two myc-binding domains and alters the expression of the gene to affect polyamine metabolism. This variant may be associated with recurrence of colorectal adenoma. We examined whether this variant also modified the susceptibility to sporadic colorectal cancer (CRC).

METHOD

The G316 > A variant was analysed in a large (n = 754) CRC case-controlled series of hospital patient volunteers (n = 627) in the Czech Republic, and the relationship with cancer risk was estimated by conditional logistic regression.

RESULTS

After adjusting for age and sex, G316 > A was associated with no decrease in CRC risk for either heterozygotes [odds ratio 0.98, 95% confidence interval (CI) 0.77-1.23] or rare allele homozygotes (odds ratio 0.92, 95% CI 0.61-1.37).

CONCLUSION

The G316 > A functional variant in the ODC gene is unlikely to make much impact on reducing CRC risk regardless of the reduction in risk found for the recurrence of colorectal adenoma.

Aspirin for primary prevention: do potential benefits outweigh the risks?

The role of aspirin for primary prevention in healthy individuals has been the subject of clinical trials for more than a quarter of a century. Because of this evidence, or sometimes despite it, many individuals self-administer aspirin to prevent cardiovascular events. This article reviews the published work for aspirin in primary prevention of cardiovascular and malignant diseases and considers whether aspirin would be approved by regulatory authorities for this use if it were to be marketed for this indication today.

Patient preferences for the chemoprevention of colorectal cancer

Although evidence suggests that aspirin and celecoxib may reduce the risk of colorectal cancer (CRC), these drugs can also cause harmful side effects. The aim of this study was to characterize patient preferences for celecoxib and aspirin. Participants completed a computer-based patient decision-making questionnaire that included an educational component outlining the benefits and harms of celecoxib and aspirin. Under the base conditions 7.4% would take celecoxib and 43.6% would take aspirin; males were more willing than females to take aspirin. Patients identified the increased risk of myocardial infarction and gastrointestinal events as the primary reasons for their unwillingness to take celecoxib and aspirin, respectively. A majority of subjects would not take either drug, after considering their benefits and harms, although participants were almost six times more likely to take aspirin than celecoxib. These data serve to inform physicians and researchers regarding the variability and factors that affect patient preferences for CRC chemoprevention.

Colon cancer: preventive agents and the present status of chemoprevention

BACKGROUND

Colorectal cancer (CRC) is one of the most common cancers worldwide and a prevalent cause of morbidity and mortality. CRC has a natural history of transition from a precursor lesion, ie adenomatous polyp to cancer, that spans over 10 to 15 years providing an extended opportunity for intervention and cancer prevention. Suppression of the carcinogenic process by use of pharmacological or natural agents is the cornerstone of chemoprevention.

OBJECTIVES

The aim of this review was to give an up-to-date overview on the different agents that had been studied, over the last decade, as chemopreventive agents and the current status of chemoprevention.

METHODS

Articles were identified by searches of PubMed and the Internet and reviewed. All articles and other referenced materials were retrieved using the keywords "colon cancer", "adenoma", "chemoprevention", "non steroidal anti-inflammatory drugs", "aspirin", "HMG-CoA reductase inhibitors", "bile acids", "Difluoromethylornithine", "hormone replacement therapy", "mesalamine", "curcumin", and "calcium". Papers were published between 1960 and 2008, with older references selected for historical significance. Only papers published in English were reviewed.

RESULTS

Recent preclinical as well as clinical trials have provided data on the potential benefit of a number of drugs and nutritional elements in the field of CRC prevention. Currently, only celecoxib is FDA approved for chemoprevention of CRC and only for high-risk patients with Familial Adenomatous Polyposis (FAP). This is mainly due to cardiovascular toxicity reported in individuals with a personal history of sporadic adenomas. Aspirin and sulindac have also repeatedly demonstrated efficacy in this setting. However, due to increased risk of associated GI toxicity their benefit will have to be weighed against their risk. Combination therapy, using lower doses of each medication, is drawing a great deal of attention and many studies utilizing a variety of chemopreventive agents are presently under study. Promising results have recently been published using sulindac and DFMO.

CONCLUSION

Many agents have shown positive results in the field of chemoprevention however, the ideal chemopreventive agent remains to be discovered with great emphasis on need not to harm. Combining different agents may maximize effectiveness while limiting drug toxicity.

Cyclooxygenase as a target for chemoprevention in colorectal cancer: lost cause or a concept coming of age?

COX-2 is upregulated at an early stage in colorectal carcinogenesis and generates prostaglandins, which promote cancer cell proliferation, impair apoptosis and enhance angiogenesis, promoting tumour growth and metastasis. There are ample data from animal models and human studies to demonstrate enhanced tumour progression associated with COX-2 activity in cancer cells. Conversely, NSAIDs including aspirin inhibit COX-2 and, therefore, have anti-neoplastic properties. There has been sustained interest in COX-2 as a chemopreventive target in colorectal cancer (CRC) and although both aspirin and COX-2 selective NSAIDs have demonstrated efficacy, adverse effects have limited their widespread adoption. In particular, evidence of the cardiovascular effects of COX-2 selective inhibitors has led to questioning of the suitability of COX-2 as a target for chemoprevention. This review examines the basis for targeting COX-2 in CRC chemoprevention, evaluates the efficacy and safety of the approach and examines future strategies in this area.

Can calcium chemoprevention of adenoma recurrence substitute or serve as an adjunct for colonoscopic surveillance?

OBJECTIVES

The aim of this study was to examine the potential cost-effectiveness of calcium chemoprevention post-polypectomy as a substitute or adjunct for surveillance.

METHODS

We constructed a Markov model of post-polypectomy adenoma recurrence and colorectal cancer (CRC) development, calibrated to data from prospective chemoprevention trials of fiber, calcium, antioxidants, and aspirin. We modeled four scenarios for 50-year-old patients immediately after polypectomy: (i) natural history with no further intervention; (ii) elemental calcium 1,200 mg/day from age 50-80; (iii) surveillance colonoscopy from age 50-80 every 5 years, or 3 years for large adenoma; (iv) calcium + surveillance. Patients were followed up until age 100 or death.

RESULTS

Calcium was cost-effective compared to natural history ($49,900/life-year gained). However, surveillance was significantly more effective than calcium (18.729 versus 18.654 life-years/patient; 76 percent versus 14 percent reduction in CRC incidence) at an incremental cost of $15,900/life-year gained. Calcium + surveillance yielded a very small benefit (0.0003 incremental life-years/patient) compared with surveillance alone, at a substantial incremental cost of $3,090,000/life-year gained.

CONCLUSION

Post-polypectomy calcium chemoprevention is unlikely to be a reasonable substitute for surveillance. It may be cost-effective in patients unwilling or unable to undergo surveillance.

Chemoprevention of colorectal cancer: feasibility in everyday practice?

Chemoprevention means the use of agents to prevent, delay, or reverse carcinogenesis. This review was designed to critically discuss the most promising agents in colorectal cancer (CRC) chemoprevention. Aspirin is the best studied chemopreventive agent for CRC. Optimal chemoprevention requires long-term use and high dose of aspirin that may increase the risk of gastrointestinal bleeding. Nonsteroidal anti-inflammatory drugs and selective cyclooxygenase-2 inhibitors may also be candidates for chemoprevention. The regular use of nonsteroidal anti-inflammatory drugs, however, causes adverse effects including gastrointestinal bleeding, and cyclooxygenase-2 inhibitors may increase the risk of cardiovascular events. In patients with ulcerative colitis 5-aminosalicylates reduce the risk of CRC and dysplasia. Ursodeoxycholic acid can reduce the risk of dysplasia or CRC in patients with primary sclerosing cholangitis and ulcerative colitis. Current data are insufficient to support the use of hormone replacement therapy to reduce the risk of CRC. Statins may have chemopreventive effects, but further investigation of their overall benefits in preventing CRC is warranted. Antioxidant supplements cannot prevent CRC. The usefulness of selenium, folate, calcium, and vitamin D awaits further evaluation. Chemoprevention cannot yet be accepted as standard medical practice. Use of chemopreventive agents cannot be a substitute for colorectal surveillance.

Willingness to pay for cancer prevention

Cancer inflicts great pain, burden and cost upon American society, and preventing cancer is important but not costless. The aim of this review was to explore the upper limits that American society is paying and appears willing to pay to prevent cancer, by enforced environmental regulations and implemented clinical practice guidelines. Cost-effectiveness studies of clinical and environmental cancer-prevention policies and programmes were identified through a comprehensive literature review and confirmed to be officially sanctioned and implemented, enforced or funded. Data were collected in 2005-6 and analysed in 2007. The incremental cost-effectiveness ratios (ICERs) for clinical prevention policies ranged from under $US2000 to over $US6 000 000 per life-year saved (LYS), exceeding $US100 000 per LYS for only 11 of 101 guidelines. Median ICERs for tobacco-related ($US3978/LYS), colorectal ($US22 694/LYS) and breast ($US25 687/LYS) cancer prevention were within generally accepted ranges and tended not to vary greatly, whereas those for prostate ($US73 603/LYS) and cervical ($US125 157/LYS) cancer-prevention policies were considerably higher and varied substantially more. In contrast, both the median and range of the environmental policies were enormous, with 90% exceeding $US100 000 per LYS, and ICERs ranging from $US61 004 to over $US24 billion per LYS. Notwithstanding a relatively large and accessible literature evaluating the cost effectiveness of clinical and environmental cancer-prevention policies as well as the availability of ICERs for the policies identified in this study, the apparent willingness to pay to prevent cancer in the US still varies greatly and can be extremely high, particularly for many of the environmental cancer-prevention policies.

Aspirin and NSAIDs for the prevention of colorectal cancer

With few exceptions, epidemiological studies have found that individuals who take nonsteroidal antiinflammatory drugs (NSAIDs) have a reduced risk of colorectal adenomas and carcinoma. Similarly, randomized studies in patients with familial adenomatous polyposis have uniformly found that NSAIDs can lead to polyp regression and prevention of new polyps, and trials in patients with sporadic adenomas document that aspirin reduces the risk of adenoma recurrence. Together these data provide convincing evidence for the chemopreventive efficacy ofNSAIDs in the large bowel.

Ornithine decarboxylase G316A genotype is prognostic for colorectal adenoma recurrence and predicts efficacy of aspirin chemoprevention

PURPOSE

The chemopreventive activity of aspirin in colorectal neoplasia may be explained in part by its effect on polyamine metabolism. The ornithine decarboxylase (ODC) G316A polymorphism affects polyamine metabolism through altered expression of ODC. We investigated the influence of ODC G316A on the chemopreventive activity of aspirin in colorectal adenoma (CRA) recurrence.

EXPERIMENTAL DESIGN

We genotyped ODC G316A in 546 individuals in the United Kingdom Colorectal Adenoma Prevention trial of aspirin for CRA recurrence prevention and pooled our findings with data from two other randomized intervention trials.

RESULTS

The United Kingdom Colorectal Adenoma Prevention participants with homozygous ODC 316AA genotype were at reduced CRA recurrence risk [relative risk (RR), 0.43; 95% confidence interval (95% CI), 0.16-1.15], particularly if also exposed to aspirin (RR, 0.24; 95% CI, 0.03-1.71). In the pooled analysis of 2,207 individuals, those with homozygous ODC 316AA genotype were at significantly reduced CRA recurrence risk (RR, 0.68; 95% CI, 0.47-0.99). Following stratification by genotype and aspirin exposure, individuals with homozygous wild-type or heterozygous genotypes derived modest benefit from aspirin (RR, 0.85; 95% CI, 0.72-1.01), whereas in those with both ODC 316AA genotype and aspirin exposure recurrence risk was halved (RR, 0.52; 95% CI, 0.29-0.91).

CONCLUSION

The ODC G316A genotype is prognostic for CRA recurrence and predictive of an enhanced response to aspirin in preventing recurrence. This variant has the potential to be a clinically useful genetic marker to identify individuals likely to derive the greatest benefit from aspirin chemoprevention.

Aspirin chemoprevention in patients with increased risk for colorectal cancer: a cost-effectiveness analysis

BACKGROUND

Aspirin chemoprevention combined with colonoscopy screening is not cost-effective for the general population. However, the cost-effectiveness of aspirin in individuals with prior adenoma resection has not been evaluated.

AIM

To evaluate the cost-effectiveness of aspirin chemoprevention alone and in combination with colonoscopy surveillance in patients with prior adenoma resection.

METHODS

A model of the natural history of individuals with a history of endoscopic polypectomy was constructed. Four strategies were compared: (i) no intervention, (ii) routine colonoscopy surveillance, (iii) aspirin chemoprevention alone, and (iv) aspirin therapy combined with colonoscopy.

RESULTS

Compared with no intervention, all other strategies were more costly but were associated with gains in years of life saved. Aspirin chemoprevention alone was associated with a gain of 0.0092 years, whereas routine colonoscopic surveillance and combination strategy were associated with further gains in years of life saved (0.0124 and 0.0138 years, respectively). Compared with no intervention, the incremental cost-effectiveness ratio of routine colonoscopy surveillance was $78,226 per year of life saved, and the incremental cost-effectiveness ratio of combination aspirin and colonoscopy was $60,942 per year of life saved.

CONCLUSION

Aspirin chemoprevention combined with colonoscopic surveillance in post-polypectomy patients may be considered a cost-effective strategy.

Surface phospholipids in gastric injury and protection when a selective cyclooxygenase-2 inhibitor (Coxib) is used in combination with aspirin

BACKGROUND AND PURPOSE

Clinical studies demonstrate that aspirin consumption reverses the gastrointestinal (GI) benefits of coxibs, by an undefined mechanism.

EXPERIMENTAL APPROACH

Rodent models were employed to investigate the effects of combinations of celecoxib and aspirin on gastric ulcerogenesis, bleeding, surface hydrophobicity (by contact angle analysis) and ulcer healing. We also evaluated the effects of phosphatidylcholine (PC)-associated aspirin in these rodent models and confirmed its cyclooxygenase (COX)-inhibitory activity by measuring mucosal prostaglandin E(2) (PGE(2)) concentration. We present evidence that aspirin's ability to induce gastric injury and bleeding in rats, was exacerbated in the presence of a coxib and was dependent on its ability to reduce gastric surface hydrophobicity. In contrast, co-administration of phosphatidylcholine (PC)-associated aspirin and celecoxib induced little or no gastric injury/bleeding and maintained the stomach's hydrophobic properties. Interestingly, aspirin and aspirin/PC equally inhibited gastric mucosal PGE(2) concentration. Aspirin in combination with a coxib retarded the healing of experimentally induced gastric ulcers, whereas healing rates of rats treated with celecoxib in combination with aspirin/PC were comparable to controls.

CONCLUSIONS AND IMPLICATIONS

Aspirin's gastric toxicity in combination with a coxib can be dissociated from its ability to inhibit COX-1 and appears to be dependent, in part, on its ability to attenuate the stomach's surface hydrophobic barrier. This adverse drug interaction between aspirin and coxibs, which impacts the treatment of osteoarthritic and cardiac patients requiring cardiovascular prophylaxis, can be circumvented by the administration of phosphatidylcholine (PC)-associated aspirin, to maintain the stomach's hydrophobic properties.

Chemoprevention of colon carcinogenesis by polyethylene glycol: suppression of epithelial proliferation via modulation of SNAIL/beta-catenin signaling

Polyethylene glycol (PEG) is one of the most potent chemopreventive agents against colorectal cancer; however, the mechanisms remain largely unexplored. In this study, we assessed the ability of PEG to target cyclin D1-beta-catenin-mediated hyperproliferation in the azoxymethane-treated rat model and the human colorectal cancer cell line, HT-29. Azoxymethane-treated rats were randomized to AIN-76A diet alone or supplemented with 5% PEG-8000. After 30 weeks, animals were euthanized and biopsies of aberrant crypt foci and uninvolved crypts were subjected to immunohistochemical and immunoblot analyses. PEG markedly suppressed both early and late markers of azoxymethane-induced colon carcinogenesis (fractal dimension by 80%, aberrant crypt foci by 64%, and tumors by 74%). In both azoxymethane-treated rats and HT-29 cells treated with 5% PEG-3350 for 24 hours, PEG decreased proliferation (45% and 52%, respectively) and cyclin D1 (78% and 56%, respectively). Because beta-catenin is the major regulator of cyclin D1 in colorectal cancer, we used the T-cell factor (Tcf)-TOPFLASH reporter assay to show that PEG markedly inhibited beta-catenin transcriptional activity. PEG did not alter total beta-catenin expression but rather its nuclear localization, leading us to assess E-cadherin expression (a major determinant of beta-catenin subcellular localization), which was increased by 73% and 71% in the azoxymethane-rat and HT-29 cells, respectively. We therefore investigated the effect of PEG treatment on levels of the negative regulator of E-cadherin, SNAIL, and observed a 50% and 75% decrease, respectively. In conclusion, we show, for the first time, a molecular mechanism through which PEG imparts its antiproliferative and hence profound chemopreventive effect.

Chemoprevention of colorectal cancer: two steps forward, one step back?

Colorectal cancer (CRC) is a leading cause of cancer-related morbidity and mortality in the Western world. The poor survival rate has prompted the emphasis on prevention of this disease. Removal of adenomas at colonoscopy is highly effective and is the cornerstone of screening/surveillance strategies. However, screening efforts have had limited impact owing to low compliance with guidelines. Chemoprevention aims to prevent the development or recurrence of precancerous lesions and cancers with the use of compounds that block the carcinogenic process. A major advantage was the establishment and understanding of the multistage process of CRC carcinogenesis. Progress has been remarkable because of the availability of reliable animal models and clinical studies using colonic adenomas as a reliable and economic target for testing chemopreventive agents. Nonsteroidal anti-inflammatory drugs have drawn the most attention. Sulindac and celecoxib were shown to be effective in promoting polyp regression in high-risk individuals with familial adenomatous polyposis. In the more common sporadic setting, the Adenomatous Polyp PRevention On Vioxx® (rofecoxib), Adenoma Prevention with Celecoxib and Prevention of Sporadic Adenomatous Polyps (celecoxib) trials have demonstrated a significant reduction in adenoma recurrence, but important concerns were raised regarding cardiovascular toxicity associated with selective cyclo-oxygenase-2 inhibitors. These landmark studies are very important, as they are a proof-of-concept that we can prevent CRC. More clinical studies are required to better select high-risk patients with safer regimens. Potential advantage versus risk for a given chemopreventive agent will have to be assessed on an individual basis. Currently, the only approved agent for chemoprevention is celecoxib in high-risk individuals with familial adenomatous polyposis.

Simultaneous fluorescence imaging of protease expression and vascularity during murine colonoscopy for colonic lesion characterization

BACKGROUND

Molecularly targeted fluorescent probes are currently being developed to improve the endoscopic detection of intestinal pathologic conditions.

OBJECTIVE

We report on the development and testing of a novel multichannel microendoscope capable of quantitatively reporting such probes simultaneously at different wavelengths in real time. We assessed the feasibility of detecting and quantifying beacons that can be activated by protease and correlating imaging with disease state.

DESIGN

The microendoscope consisted of a 20-gauge fiberoptic catheter and dichroic beam splitters that simultaneously display visible light, 700 nm and 800 nm near infrared (NIR) fluorescent light. NIR interchannel separation was tested on in vitro phantoms. Two mouse models were used (Apcmin(+/-) mice for colonic adenomas and CT26 murine colon cancer). A perfusion probe and one activated by protease at a separate wavelength were injected before endoscopic evaluation.

RESULTS

The microendoscope fluorochrome detection limit was approximately 10 fmol; ratio imaging in the NIR was accurate (+/-8% of true probe concentration between 0.3 to 100 microg/ml of a protease sensor). Both colonic adenomas and adenocarcinomas were clearly visible in the NIR channel on protease probe administration in live mice. Ratio imaging of protease activity/perfusion increased from healthy colon to adenomas to adenocarcinomas.

LIMITATIONS

Evaluation across additional spontaneous tumor models may provide more data on the translation of these findings.

CONCLUSIONS

Our data show the feasibility of multichannel microendoscopic imaging of molecular targets in vivo and that ratio imaging may provide a novel means for characterizing colonic lesions. When scaled up clinically, this could aid in increasing lesion detection and quantitative assessment of distinct molecular markers.

Does a selective cyclooxygenase-2 inhibitor (tiracoxib) induce clinically sufficient suppression of adenomas in patients with familial adenomatous polyposis? A randomized double-blind placebo-controlled clinical trial

BACKGROUND

There have been few placebo-controlled randomized double-blind studies of the clinical effects of selective cyclooxygenase-2 (COX-2) inhibitors on the regression of colorectal tumors. This study was designed to examine the regressive effect of a selective COX-2 inhibitor, tiracoxib (JTE-522), on colorectal polyps in patients with familial adenomatous polyposis (FAP), and its safety.

METHODS

Sixty-one patients with FAP diagnosed by Japanese criteria were assigned randomly to receive placebo or JTE-522, at either 150 mg or 200 mg, once daily orally for 26 weeks. Prior to and at the end of the medication period, endoscopy was performed. Adenomas located near an india-ink tattoo injected at the first colonoscopy were identified and measured. The response variables were the percent changes from the baseline in polyp numbers and in specified polyp diameters. Any adverse events that appeared in at least four persons were taken into consideration and compared between the JTE-522 treatment groups and the placebo group.

RESULTS

No change in polyp number (median, 0) was observed in any of the three groups. There were no differences between the placebo group and the two treatment groups in the change in polyp size. JTE-522 was well tolerated.

CONCLUSION

Our findings, in keeping with other reports on COX-2 inhibitors, indicated that the inhibition of a COX-2 with a moderate dose of a selective COX-2 inhibitor did not induce clinically sufficient regression of adenomas in patients with FAP in a limited (6-month) medication period.

Chemoprevention of colorectal cancer with nonsteroidal anti-inflammatory drugs

Colorectal carcinoma is one of the commonest solid organ tumors in the world and its prevalence appears to be increasing in Asia. Recently, there has been much interest in various chemotherapeutic agents for the management of this condition, in particular nonsteroidal anti-inflammatory drugs (NSAIDs). There is a large amount of data that suggest traditional NSAIDs, as well as the new cyclooxygenase (COX)-2 selective inhibitors such as rofecoxib and celecoxib, have a role in the setting of primary and secondary prevention, and adjuvant therapy of both sporadic colorectal carcinoma and familial adenomatous polyposis. This review examines some of this data, as well as the potential problems and limitations of using these agents, particularly in light of the recent withdrawal of rofecoxib.

[Cost-effectiveness of colorectal cancer screening]

Colorectal cancer (CRC) screening in France is based on a faecal occult blood test every two years in average risk subjects 50-74 years of age while other endoscopic or non-endoscopic screening methods are used in Europe and in the USA. Beside the reduced incidence of and mortality from CRC found in available studies, cost-effectiveness data need to be taken into account. Because of the delay between randomized controlled trials and clinical results, transitional probabilistic models of screening programs are useful for public health policy makers. The aim of the present review was to promote the implementation of cost-effectiveness studies, to provide a guide to analyze cost-effectiveness studies on CRC screening and, to propose a French cost effectiveness study comparing CRC screening strategies. Most of these trials were performed by US or UK authors and demonstrate that the incremental cost-effectiveness ratio varies between 5 000 and 15 000 US dollars/one year life gained, with wide variations: these results were highly dependent on the unit costs of the different devices as well as the predictive values of the screening tests. Although CRC screening programs have been implemented in several administrative districts of France since 2002, and the results of these randomized controlled trials using fecal occult blood have been updated, cost-effectiveness criteria need to be integrated; especially since the results of screening campaigns based on other tools such as flexible sigmoidoscopy should be available in 2007.

Potential role of flavonoids in the prevention of intestinal neoplasia: a review of their mode of action and their clinical perspectives

Intestinal neoplasia (adenomas and carcinomas) can possibly be prevented by a diet rich in vegetables and fruits, treatment with aspirin and other nonsteroidal antiinflammatory drugs, and early colonoscopic removal of adenomas. Ballast, fiber, and secondary plant products could play a major role in colon cancer prevention. Recently there has been much experimental work in vitro and in vivo about flavonoids as inducers of bioprevention. Flavonoids are secondary plant products with a wide variety of beneficial biological properties, and they possess anticarcinogenic, antimutagenic, and antioxidative modes of actions. Flavonoids are the main components of a healthy diet containing fruits and vegetables and are concentrated especially in tea, apples, and onions. We will focus this review on flavonoids which are derived from tea products such as proanthocyanidins (green tea) and flavons (camomille tea). Oral supplementation with bioflavonoids derived from tea could be used in humans to prevent growth of intestinal neoplasia such as adenomatous polyps of the colon. Flavonoids are a large group of natural compounds of which only a few have been used in animal models, cell cultures, and enzyme studies to inhibit mutagenic and carcinogenic events. Their clinical mode of action was evaluated by epidemiological studies, but no intervention studies in humans have been performed so far. In vitro flavonoids can bind electrophils, inactivate oxygen radicals, prevent lipid peroxidation, and inhibit DNA oxidation. In cell cultures they increase the rate of apoptosis, inhibit cell proliferation, and angiogenesis. In vivo they can induce the activities of protective enzymes (conjugating enzymes such as glutathione transferases and glucuronosyl transferases) of the intestine and the liver. In models of intestinal polyposis, flavonoids suppress polyp formation. Some epidemiological studies show a protective effect of flavonoids contained in fruits, vegetables, and tea. Flavonoid mixtures of tea origin supplied as nutritional supplements could be studied as a new way of bioprevention of intestinal neoplasia (colon adenomas and cancer). Therefore, a controlled, randomized clinical study should be performed to evaluate the efficacy of flavonoids.

Colorectal cancer prevention: is an ounce of prevention worth a pound of cure?

Colorectal cancer (CRC) is among the most common human malignancies and remains a leading cause of cancer-related morbidity and mortality. Colorectal carcinogenesis is a multistep process characterized by molecular and cellular alterations that result in an identifiable precursor lesion, ie, the adenomatous polyp. The transition from normal mucosa to adenoma and its subsequent progression to carcinoma are protracted events that offer opportunities for preventive interventions. Suppression or reversal of the carcinogenic process in the colorectum with nonpharmacologic or pharmacologic agents, ie, chemoprevention, is an area of considerable research interest and activity. Interest in this field derives from multiple epidemiologic studies showing that regular and continued use of nonsteroidal anti-inflammatory drugs (NSAIDs), predominantly aspirin, is associated with significant reductions in both colorectal adenoma and carcinoma incidence. NSAIDs were first shown to be effective in patients with familial adenomatous polyposis (FAP). Subsequent randomized trials in FAP demonstrated that sulindac and the selective cyclooxygenase-2 (COX-2) inhibitor, celecoxib, can significantly regress existing adenomas, and resulted in Food and Drug Administration (FDA) approval of celecoxib for adjunctive management of these patients. Based on the aforementioned data, aspirin and coxibs have been or are currently being evaluated for the prevention of sporadic adenoma recurrence in high-risk patient populations. Evidence indicates that aspirin can reduce adenoma recurrence rates in patients with prior colorectal neoplasia; however, questions remain, including the optimal dosage, timing of initiation and duration of treatment, and clinical benefit versus potential harm to patients. These same issues apply to the nonpharmacologic agents such as calcium, folic acid, and selenium given as dietary supplements. Apart from aspirin, calcium carbonate is the only other agent that has been shown to modestly reduce sporadic adenoma recurrence rates in a randomized trial. Folate and selenium are being actively studied based on provocative preclinical data. In addition to demonstrating efficacy, chemopreventive agents must also be safe for long-term use, be well accepted by patients, and be cost-effective. In this review, the current status of CRC chemoprevention will be discussed, including the available evidence for selected pharmacologic and nonpharmacologic agents, particularly among high-risk populations.

Review article: the potential of combinational regimen with non-steroidal anti-inflammatory drugs in the chemoprevention of colorectal cancer

Non-steroidal anti-inflammatory drugs are chemopreventive agents in colorectal cancer. Non-steroidal anti-inflammatory drugs do not, however, offer complete protection against adenoma and carcinoma development. There is increasing interest in combining non-steroidal anti-inflammatory drugs with agents that target specific cell signalling pathways in malignant and premalignant cells. This review aims to describe the current knowledge regarding the efficacy of peroxisome proliferator-activated receptor-gamma ligands, cholesterol synthesis inhibitors (statins), epidermal growth factor signalling inhibitors and tumour necrosis factor-related apoptosis-inducing ligand against colorectal neoplasms and the rationale for combining these drugs with non-steroidal anti-inflammatory drugs to improve efficacy in the chemoprevention of colorectal cancer, a PUBMED computer search of the English language literature was conducted to identify relevant papers published before July 2004. Peroxisome proliferator-activated receptor-gamma ligands and statins, both in clinical use, reduce the growth rate of human colon cancer cells in vitro and in rodents models. In vitro, preclinical in vivo and clinical studies have shown efficacy of epidermal growth factor signalling inhibition in colorectal cancer. In vitro, tumour necrosis factor-related apoptosis-inducing ligand induces apoptosis in human colon cancer cells, but not in normal cells. These drugs have all been shown to interact with non-steroidal anti-inflammatory drugs in colorectal cancer cells and/or in rodent models. Combinational regimen are a promising strategy for the chemoprevention of colorectal cancer and should be further explored.

Review article: monitoring of immunomodulators in inflammatory bowel disease

The armamentarium of medications for the treatment of inflammatory bowel disease is growing and becoming more complicated to use. Immunomodulators are a class of medications that have found a niche for the treatment of Crohn's disease and ulcerative colitis. Because of the mounting supporting evidence for efficacy, the most commonly-used immunomodulators are azathioprine, mercaptopurine, methotrexate and ciclosporin. These medications are being used more often due to their steroid-sparing and potentially surgery-sparing effects. Immunomodulators are also known for a significant side-effect profile and require careful monitoring. This review provides the latest information for clinicians on efficacy, side-effects, dosing and monitoring of these medications for treatment of inflammatory bowel disease.

Strategies for prevention of colorectal cancer: Pharmaceutical and nutritional interventions

Interventions designed to delay or prevent the development of invasive colorectal adenocarcinoma might result in a profound impact on the incidence of and mortality from colorectal cancer. Current developmental efforts focus in two major directions: identification and testing of combination-targeted signal transduction pathway modulators and development of nutriceuticals. Both approaches recognize the heterogeneity of the carcinogenesis process. Combinations of agents (eg, aspirin or sulindac with DFMO, calcium with fiber), which have complementary or synergistic mechanisms or agents with broad spectrum anti-carcinogenic effects can potentially improve upon the effects of single agents and account for redundant signal transduction pathways involved in uncontrolled growth of clonal cells. Preliminary data in rodent systems suggest nutriceuticals or standardized foodstuffs, which contain multiple components, many of which are not identified have synergistic anticarcinogenesis effects. Diet modulation or supplementation with known standardized foodstuffs may be ideal in individuals at risk for colorectal cancer. Current clinical models for colorectal cancer prevention focus upon a pathologic-surrogate endpoint (reducing the recurrence or emergence of adenomas). This surrogate, generally accepted at a regulatory level, might not represent the true malignant progression from normal colonic mucosa to the malignant phenotype. Could the intervention simply prevent the emergence of adenomas that would not have progressed to invasive neoplasia in any event? Despite this major weakness, the adenoma remains the regulatory endpoint for efficacy because the cancer event remains rare, even among individuals selected as high-risk epidemiology but without known, highly pressured genetic-based stress. Over the next decade, the emergence of molecular and proteomic profiling tools have the potential of selecting adenomas that will progress to adenocarcinomas and will allow for investigation to be focused on individuals at increased risk.

Non steroidal anti-inflammatory drugs (NSAID) and Aspirin for preventing colorectal adenomas and carcinomas

EDITORIAL NOTE

This review was split in 2012 and the review question was to be addressed according to three new protocols: (See: http://www.cochranelibrary.com/cdsr/doi/10.1002/14651858.CD010267.pub2; http://www.cochranelibrary.com/cdsr/doi/10.1002/14651858.CD010291.pub2; http://www.cochranelibrary.com/cdsr/doi/10.1002/14651858.CD010325.pub2). These titles were withdrawn at the protocol stage in 2020 as the authors did not make any progress on the reviews. This original review will no longer be updated and may be superseded by new titles hosted by Cochrane Gut in the future.

BACKGROUND

There is evidence from experimental animals studies, prospective and retrospective observational studies that nonsteroidal anti-inflammatory drugs (NSAIDS) may reduce the development of sporadic colorectal adenomas (CRAs) and cancer (CRC) and may induce the regression of adenomas in familial adenomatous polyposis (FAP).

OBJECTIVES

To conduct a systematic review to determine the effect of NSAIDS for the prevention or regression of CRAs and CRC.

SEARCH STRATEGY

Randomized controlled trials (RCTs) up to September 2003 were identified.

SELECTION CRITERIA

NSAIDS and aspirin (ASA) were the interventions. The primary outcomes were the number of subjects with at least one CRA, the change in polyp burden, and CRC. The secondary outcome was adverse events.

DATA COLLECTION AND ANALYSIS

Two reviewers independently extracted data and assessed trial quality. Dichotomous outcomes were reported as relative risks (RR) with 95% confidence intervals (CI). The data were combined with the random effects model if clinically and statistically reasonable.

MAIN RESULTS

Nine trials with 150 familial adenomatous polyposis (FAP) and 24,143 population subjects met the inclusion criteria. The interventions included sulindac, celecoxib, or aspirin (ASA). From the combined results of three trials, significantly fewer subjects in the low dose ASA group developed recurrent sporadic CRAs [RR 0.77 (95% CI 0.61, 0.96), (NNT 12.5 (95% CI 7.7, 25)] after one to three years. In another three trials, phenotypic FAP subjects that received sulindac or celecoxib had a greater proportional reduction (range: 11.9% to 44%) in the number of CRAs compared to those in the control group (range: 4.5% to 10%). There was no significant difference for the outcomes of CRC or adverse events in any of the trials.

REVIEWERS' CONCLUSIONS

There was evidence from three pooled RCTs that ASA significantly reduces the recurrence of sporadic adenomatous polyps after one to three years. There is evidence from short-term studies to support regression, but not elimination or prevention of CRAs in FAP.

Potential cost-effectiveness of colorectal cancer chemoprevention with nonsteroidal anti-inflammatory drugs

Colorectal cancer is the second leading cause of cancer-related death in the Western world. Screening for colorectal neoplasia, including the removal of adenomas, is highly effective and cost-effective in reducing colorectal cancer incidence and mortality. However, only a minority of the population is currently screened. Based on data from animal models, observational studies and randomized trials in humans, nonsteroidal anti-inflammatory drugs appear to have great promise as chemopreventive agents against colorectal cancer. The critical factors that will determine the roles of aspirin, other nonselective nonsteroidal anti-inflammatory drugs and selective cyclooxygenase-2 inhibitors in colorectal cancer chemoprevention include the magnitude of their protective effect, their risks, their costs, the treated population's characteristics, treatment adherence rates and how chemoprevention compares with established screening strategies.

Preventing cancer: dietary lifestyle or clinical intervention?

In Australia, colorectal, prostate and breast cancers are the most frequently occurring cancers in our society, a pattern that is quite different from that of underdeveloped countries. While diet is largely responsible for these differences, technological advances mean that the solutions can be viewed as systematic, financial, lifestyle or technological. They range from those that require self-discipline and care for personal well-being through to those that are seemingly a quick technological fix that will work in spite of an unhealthy lifestyle. There are three main approaches available for prevention of these cancers: dietary lifestyle, chemoprevention and screening. It has been estimated that the potential for prevention by a healthy dietary lifestyle is excellent and might reduce the burden of breast, prostate and colorectal cancer by 33-55%, 10-20% and 66-75%, respectively. This should be safe and inexpensive and have collateral benefit such as reduced cardiovascular disease and osteoporosis. But, population compliance with more plant-based, less calorie dense foods is uncertain, the most healthy are likely to be the most compliant and evidence for effectiveness when interventional programs are undertaken is disappointing. It is not clear how dependable the dietary approach would be where inherited genetic factors determine risk for one of these cancers. Chemoprevention, the administration of natural or synthetic agents that delay, slow down or inhibit the process of tumorigenesis, are still under development and study. Hormone receptor modulators for breast and derivatives of non-steroidal anti-inflammatory drugs for colorectal cancers seem to have most promise and may reduce tumour incidence or death by as much as 50%. These agents are simpler to comply with than changing dietary lifestyle and they are more potent, hence they may be of particular value in high-risk settings. But they are likely to be more costly and run the risk of adverse effects with few collateral benefits. Screening, or the testing of an individual for a disease when that individual does not have any symptoms or signs suggesting that the disease is present, aims to prevent or delay the development of the cancer. Screening impacts on mortality more so than on incidence, reducing colorectal cancer mortality in the range 15-60% and breast cancer mortality by 23-37%. Screening has the advantage of being effective in high-risk as well as average-risk groups and is an 'easy' solution for the person who elects not to follow a healthy dietary lifestyle. Nonetheless, it is expensive, demanding on resources, provides no collateral benefits and does not have the same potential to reduce incidence of disease as does the dietary approach. With these Western cancers, we are fortunate that there are options for prevention. At least choices are available and some will suite certain circumstances and personalities more than others.

Potential effect of cyclooxygenase-2-specific inhibitors on the prevention of colorectal cancer: a cost-effectiveness analysis

PURPOSE

To estimate the potential cost-effectiveness of colorectal cancer chemoprevention with cyclooxygenase-2-specific inhibitors (COX-2 inhibitors).

METHODS

Using a decision analytic Markov model, we estimated the discounted cost per life-year saved for three strategies: a COX-2 inhibitor alone; as an adjunct to colonoscopy every 10 years in persons at average risk of colorectal cancer; and as an adjunct to colonoscopy every 5 years in persons with first-degree relatives who had colorectal cancer.

RESULTS

In the base case, the incremental cost per life-year saved with a COX-2 inhibitor alone compared with no screening was 233,300 dollars in persons at average risk of colorectal cancer and 56,700 dollars in persons with 2 first-degree relatives who had the disease. Chemoprevention was both less effective and more costly than screening. The incremental cost per life-year saved with a COX-2 inhibitor as an adjunct to screening was 823,800 dollars in persons at average risk and 404,700 dollars in persons with 2 first-degree relatives who had colorectal cancer. Combining a COX-2 inhibitor with less frequent screening was not as cost-effective as screening at currently recommended intervals. Cost-effectiveness estimates were highly sensitive to the cost of COX-2 inhibitors and their effect on the risk of cancer.

CONCLUSION

Chemoprevention of colorectal cancer with COX-2 inhibitors is likely to incur substantially higher costs per life-year saved than are currently recommended screening strategies. COX-2 inhibitor use as an adjunct to screening may increase life expectancy, although at prohibitive costs, and is unlikely to result in less frequent screening.

A randomized trial of aspirin to prevent colorectal adenomas in patients with previous colorectal cancer

BACKGROUND

Experimental studies in animals and observational studies in humans suggest that regular aspirin use may decrease the risk of colorectal adenomas, the precursors to most colorectal cancers.

METHODS

We conducted a randomized, double-blind trial to determine the effect of aspirin on the incidence of colorectal adenomas. We randomly assigned 635 patients with previous colorectal cancer to receive either 325 mg of aspirin per day or placebo. We determined the proportion of patients with adenomas, the number of recurrent adenomas, and the time to the development of adenoma between randomization and subsequent colonoscopic examinations. Relative risks were adjusted for age, sex, cancer stage, the number of colonoscopic examinations, and the time to a first colonoscopy. The study was terminated early by an independent data and safety monitoring board when statistically significant results were reported during a planned interim analysis.

RESULTS

A total of 517 randomized patients had at least one colonoscopic examination a median of 12.8 months after randomization. One or more adenomas were found in 17 percent of patients in the aspirin group and 27 percent of patients in the placebo group (P=0.004). The mean (+/-SD) number of adenomas was lower in the aspirin group than the placebo group (0.30+/-0.87 vs. 0.49+/-0.99, P=0.003 by the Wilcoxon test). The adjusted relative risk of any recurrent adenoma in the aspirin group, as compared with the placebo group, was 0.65 (95 percent confidence interval, 0.46 to 0.91). The time to the detection of a first adenoma was longer in the aspirin group than in the placebo group (hazard ratio for the detection of a new polyp, 0.64; 95 percent confidence interval, 0.43 to 0.94; P=0.022).

CONCLUSIONS

Daily use of aspirin is associated with a significant reduction in the incidence of colorectal adenomas in patients with previous colorectal cancer.

Update on the cost-effectiveness of screening for colorectal neoplasia

Colorectal cancer is an ideal target for population screening because it is a prevalent disease with an identifiable precursor lesion that, when treated, favorably alters the natural history of the disease. Several strategies for screening have illustrated efficacy, including fecal occult blood testing, sigmoidoscopy and colonoscopy. Cost-effectiveness analyses have been performed to determine whether the resources required to implement screening are justified by potential gains. The U.S. Preventive Services Task Force recently commissioned a study on the cost-effectiveness of colorectal cancer screening, which revealed that screening was cost-effective compared to no screening. However, it could not be confirmed which strategy would save the most life-years, nor which was most cost-effective. Since publication of this review, several additional cost-effectiveness analyses have been performed. These studies confirm that screening average risk patients at age 50 by a variety of available strategies is likely to be reasonable by current standards for resource utilization, and that either colonoscopy every 10 years (or once at age 65) or the combination of annual fecal occult blood testing with sigmoidoscopy every 5 years are viable alternatives. Additional economic analyses have examined the use of aspirin chemoprophylaxis to prevent colorectal cancer either alone or as an adjunct to screening strategies. These studies reaffirm the cost-effectiveness of colorectal cancer screening, but illustrate that aspirin chemoprophylaxis is unlikely to be associated with gains for which society would be willing to pay. At present, the decision to choose one colorectal screening strategy over another is based on availability of screening modalities, patient and provider preferences, and associated adherence to screening recommendations. Assessment of preference and development of interventions to increase adherence to screening should be a focus of research in the future.

Cost-effectiveness in the prevention of colorectal cancer

In cost-effectiveness analyses of cancer prevention, the ratio of cost and medical effectiveness serves as the primary measure for comparing various strategies, effectiveness being measured in terms of (quality adjusted) life-years gained through medical intervention. Such analyses are reliable in comparing different medical management strategies and revealing the most important factors to influence their cost-effectiveness ratios, but less helpful in judging the general merit of a given medical strategy. Models of medical decision making are used to simulate the natural history of colorectal cancer and test how it becomes affected by various means of screening and prevention. The analyses suggest that, compared with no prevention, a single colonoscopy at age 65 is the most cost-effective means of cancer prevention in the general population, followed by screening colonoscopy every ten years or screening colonoscopy every ten years plus chemoprevention with daily aspirin. Other means of prevention, involving annual fecal occult blood testing or flexible sigmoidoscopy every 5-10 years, are dominated by cheaper and more effective strategies. Economic and decision models do not obviate the primacy of clinical data gathered through controlled clinical trials, since they cannot account for all factors that may eventually determine the cost-effectiveness of actual screening and cancer prevention.

Therapeutic utility of aspirin in the ApcMin/+ murine model of colon carcinogenesis

BACKGROUND

In recent years it has become evident that nonsteroidal anti-inflammatory drugs, in particular aspirin represent a potential class of cancer chemotherapeutic agents. Despite the wealth of knowledge gained from epidemiological, clinical and animal studies, the effectiveness of aspirin to treat established gastrointestinal cancer has not been determined. The present study examines the ability of aspirin to treat established polyposis in Min/+ mice.

METHODS

Min/+ mice with established polyposis were treated orally once daily from 12-16 weeks of age with either drug vehicle or aspirin (25 mg/kg). Upon completion of treatment, the number, location and size of intestinal tumours was determined. Additional variables examined were the number of apoptotic cells within tumours and COX activity.

RESULTS

Administration of aspirin for 4 weeks to Min/+ mice produce no effect on tumour number compared to vehicle-treated Min/+ mice (65 +/- 8 vs. 63 +/- 9, respectively). In addition, aspirin had no effect on tumour size or location. However, aspirin treatment produced a greater than 2-fold (p<0.05) increase in the number of apoptotic positive cells within tumours and significantly decreased hepatic PGE2 content.

CONCLUSIONS

Aspirin was found to have no effect on tumour number and size when administered to Min/+ mice with established polyposis. The findings in the present study call in to question the utility of aspirin as a stand-alone treatment for established GI cancer. However, aspirin's ability to significantly promote apoptosis may render it suitable for use in combinatorial chemotherapy.