Chemoprevention of colorectal cancer: problems, progress, and prospects

Chemoprevention of Melanoma: Theoretical and Practical Considerations

BACKGROUND

Chemoprevention refers to the use of agents to reverse, suppress, or prevent carcinogenic progression of cancer. The use of chemoprevention is an unexplored strategy in melanoma prevention.

METHODS

A retrospective review of the literature was undertaken regarding the important elements in evaluating chemoprevention as a strategy in melanoma.

RESULTS

Several considerations need to be addressed before a chemoprevention agent can be moved to a large randomized trial. Statins have both experimental and epidemiologic evidence to support their further development as candidate chemopreventive agents, but the evidence is insufficient to justify large-scale phase III studies. A strong scientific rationale, a systematic approach to chemoprevention agent development with rigorous chemoprevention designs, and careful selection of surrogate endpoint biomarkers are critical issues in developing a chemoprevention strategy.

CONCLUSIONS

Addressing these relevant considerations will allow for the development of chemoprevention in melanoma.

Chemoprevention of colorectal neoplasia

BACKGROUND

Colorectal cancer is a common and often fatal malignancy. Currently, the modifications that alter disease outcome include early symptom recognition, population screening as well as improved surgical and adjuvant treatments. Preventative strategies have been limited with little evidence that lifestyle changes significantly alter risk. There is however a growing awareness of a potential role for chemoprevention in some patient groups. This study aimed to review the literature associated with chemoprevention in colorectal cancer.

METHODS

An electronic literature search of MEDLINE and Embase databases was performed on PubMed for studies detailing the use of chemoprevention agents in colon and rectal cancer. The search was limited to clinical trials on adult humans (>16 years of age) published in English since 1990.

RESULTS

The strongest evidence is for non-steroidal anti-inflammatory drugs slowing polyp progression, notably Sulindac and aspirin in patients with familial adenomatous polyposis and hereditary nonpolyposis colorectal cancer, respectively. There is also increasing evidence that continuing use of low-dose aspirin reduces long-term incidence of colorectal cancers. Cyclooxygenase 2 inhibitors also have a potential role but cardiac toxicity currently limits their use. Folic acid, statins, antioxidants, calcium and 5-aminosalicylic acid lack evidence to support their use at present.

CONCLUSIONS

Currently, there is not enough evidence to support the implementation of a chemopreventative agent for general use. However, there appears to be a role for aspirin in selected subgroups.

Impact of deprivation on short- and long-term outcomes after colorectal cancer surgery

Background

The aim of the study was to determine the association between short- and long-term outcomes and deprivation for patients undergoing operative treatment for colorectal cancer in the Northern Region of England.

Methods

This was a retrospective analytical study based on the Northern Region Colorectal Cancer Audit Group database for the period 1998–2002. The Index of Multiple Deprivation 2004, an area-based measure, was recalibrated and used to quantify deprivation. Patients were ranked based on their postcode of residence and grouped into five categories.

Results

Of 8159 patients in total, 7352 (90·1 per cent) had surgery; 6953 (94·6 per cent) of the 7352 patients underwent tumour resection and 4935 (67·7 per cent) of 7294 had a margin-negative (R0) resection. Deprivation was not associated with age, sex, tumour site, stage or other tumour-related factors. Compared with the most affluent group, the most deprived patients had fewer elective operations (72·9 versus 76·4 per cent; P = 0·014), more adverse co-morbidity (P < 0·001) and fewer curative resections (65·5 versus 71·2 per cent; P < 0·001). In multivariable analysis, deprivation was not an independent predictor of postoperative death (odds ratio (OR) 0·72, 95 per cent confidence interval 0·48 to 1·06; P = 0·101) but it was a predictor of curative resection (OR 1·24, 1·01 to 1·52; P = 0·042), overall survival (HR 0·83, 0·73 to 0·95; P = 0·006) and relative survival (HR 0·74, 0·58 to 0·95; P = 0·023).

Conclusion

Deprivation, both independently and by influencing other surgical predictors, impacts on short- and long-term outcomes of patients with colorectal cancer.

Development and validation of a high-performance liquid chromatography method for the simultaneous determination of aspirin and folic acid from nano-particulate systems

Attention has shifted from the treatment of colorectal cancer (CRC) to chemoprevention using aspirin and folic acid as agents capable of preventing the onset of colon cancer. However, no sensitive analytical method exists to simultaneously quantify the two drugs when released from polymer-based nanoparticles. Thus, a rapid, highly sensitive method of high-performance liquid chromatography analysis to simultaneously detect low quantities of aspirin (hydrolyzed to salicylic acid, the active moiety) and folic acid released from biodegradable polylactide-co-glycolide (PLGA) copolymer nanoparticles was developed. Analysis was done on a reversed-phase C(18) column using a photodiode array detector at wavelengths of 233 nm (salicylic acid) and 277 nm (folic acid). The mobile phase consisted of acetonitrile-0.1% trifluoroacetic acid mixture programmed for a 30 min gradient elution analysis. In the range of 0.1-100 microg/mL, the assay showed good linearity for salicylic acid (R(2) = 0.9996) and folic acid (R(2) = 0.9998). The method demonstrated good reproducibility, intra- and inter-day precision and accuracy (99.67, 100.1%) and low values of detection (0.03, 0.01 microg/mL) and quantitation (0.1 and 0.05 microg/mL) for salicylic acid and folic acid, respectively. The suitability of the method was demonstrated by simultaneously determining salicylic acid and folic acid released from PLGA nanoparticles.

Nanoparticulate delivery of novel drug combination regimens for the chemoprevention of colon cancer

The purpose of this work was to assess synergistic inhibitory responses of a novel chemopreventive combination regimen of drugs namely, aspirin in combination with calcium and folic acid on two human colon cancer cell lines, HT-29 and SW-480. Subsequently, based on positive responses, nanotechnology-based formulations were developed for the targeted delivery of these combinatorial regimens to the colon for the chemoprevention of colon cancer. Additionally, conventional drug formulations using controlled release polymers chitosan, pectin and hydroxypropyl methylcellulose (HPMC) were tested for release of the drugs, for comparison purposes. Chemopreventive combination regimens demonstrated significant synergistic efficacy in both cell lines from XTT assay studies, when compared to the effects of individual agents. Approximately 45% decrease in cell viability for aspirin (15 mM) and calcium (30 mM) mixtures was observed in HT-29 cell lines, compared to approximately 55% decrease by the same combination in SW-480 cell lines. With combinations of aspirin (5 mM) and folic acid (1.5 mM), HT-29 cells demonstrated a 30% decrease in cell viability compared to approximately 38% decrease in the SW-480 cell line. Overall, all drug combinations demonstrated significant synergistic responses in the cell lines tested with the SW-480 cell line being more significantly affected by the drug regimens than the HT-29 cell line. Drug encapsulated nanoparticles demonstrated a spherical morphology, <125 nm average particle size (aspirin and folic acid) of nanoparticles and encapsulation efficiencies in the range of 80-91%. Drug release from nanoparticles was controlled with approximately 60% of the original amount released over a 96 h period. Conventional formulations exhibited faster kinetics of drug release when compared to the PLGA nanoparticles. Overall, the cell line studies demonstrate, for the first time, the ability of novel chemopreventive combinations to inhibit the growth of colon cancer cells whereas the nanotechnology-based drug delivery system provides valuable evidence for targeted therapy towards colon cancer chemoprevention.

Survey of unaffected BRCA and mismatch repair (MMR) mutation positive individuals

Many individuals do not proceed with cancer predisposition testing due to fears of genetic discrimination (GD). We report the results of a survey of 47 unaffected, mutation positive individuals regarding insurance outcomes. Participants recruited from six different Cancer Risk Programs across the country were queried about their experiences with health, life, and disability insurance, as well as employment issues. Eighty-seven percent of participants carried a BRCA mutation and 87% were part of a group insurance plan at the time of testing. Forty-seven percent of participants self-paid for testing. Less than 10% of participants reported that their results were placed in the general medical record, while 43% did not know where their results were placed. Due to concerns about GD, 13% of participants stated they avoided changing jobs. Thirteen percent stated that their at-risk relatives had not undergone testing for the familial mutation due to fears about GD. Adverse events following genetic testing included two denials from private health insurers, one denial for average life insurance coverage and one denial for additional disability insurance. There were no reports of job discrimination. Results suggest fear of GD is prevalent, yet data do not support evidence that GD exists.

Clinical predictors of colorectal polyps and carcinoma in a low prevalence region: Results of a colonoscopy based study

AIM: To estimate the prevalence of colorectal cancer (CRC) in patients with long lasting colonic symptoms undergoing total colonoscopy; and to establish clinical features predicting its occurrence.

METHODS: This prospective study was carried out in Imam Hospital, Tabriz University of medical sciences, Iran. Continuous patients with long lasting lower gastrointestinal tract symptoms who had the criteria of a colonoscopy were included. The endoscopist visualized the caecum documented by a photo and/or a specimen from terminal ileum.

RESULTS: Four hundred and eighty consecutive symptomatic patients [mean age (SD): 42.73 (16.21)] were included. The prevalence of colorectal neoplasia was 15.3% (34 subjects) and 37.7% (181 subjects) had a completely normal colon. Adenomatous polyps were detected in 56 (11.7%) patients, in 12.3% of men and 10.9% of women. The mean age of the patients with a polyp was significantly higher than the others (49.53 ± 14.16 vs 41.85 ± 16.26, P = 0.001). Most of the adenomatous polyps were left sided and tubular; only 22.5% of polyps were more than 10 mm. Cancer was detected in 16 (3.6%) of our study population, which was mostly right sided (57.2%). The mean age of patients with cancer was significantly higher than the others (60.25 ± 8.26 vs 42.13 ± 16.08, P < 0.005) and higher than patients with polyps [60.25 (8.26) vs 49.53 (1.91) (P < 0.0005)]. None of the symptoms (diarrhea, abdominal pain, rectal bleeding, constipation, altering diarrhea and constipation, history of cancer, known irritable bowel disease, history of polyp and fissure or family history of cancer) were predictors for cancer or polyps, but the age of the patient and unexplained anemia independently predicted cancer.

CONCLUSION: Less advanced patterns and smaller sizes of adenomas in Iran is compatible with other data from Asia and the Middle East, but in contrast to western countries. Prevalence of colonic neoplasia in our community seems to be lower than that in western population. Colonic symptoms are not predictors for polyps or cancer but unexplained anemia and elder age can predict CRC.

Statin use and the risk of 10 cancers

BACKGROUND

Statins affect the proliferation, survival, and migration of cancer cells, and it is thought that they may have chemopreventive properties in humans. The purpose of the present study was to evaluate the association between statin use and various types of cancer in our hospital-based case-control surveillance study.

METHODS

Data were collected from patients ages 40-79 years who were admitted to participating hospitals in 3 centers in Philadelphia, New York, and Baltimore from 1991 to 2005. Nurses administered questionnaires to obtain information on medication use and other factors. We compared patients who had any of 10 types of cancer (a total of 4913 patients) with controls admitted for noncancer diagnoses (3900 patients). The following cancers were examined individually: female breast (n = 1185), prostate (n = 1226), colorectal (n = 734), lung (n = 464), bladder (n = 240), leukemia (n = 254), pancreas (n = 220), kidney (n = 226), endometrial (n = 220), and non-Hodgkin lymphoma (n = 144). Logistic regression models were used to estimate odds ratios and 95% confidence intervals among regular statin users compared with never-users.

RESULTS

Odds ratios were compatible with 1.0 for all cancer types. For the 4 largest cancer sites (breast, prostate, colorectum, and lung), odds ratios did not vary significantly by duration of statin use.

CONCLUSIONS

Statins are among the most commonly used medications, and durations of use are increasing. The present data do not support either positive or negative associations between statin use and the occurrence of 10 cancer types. Cancer incidence should continue to be monitored among statin users.

[Identification and management of HNPCC syndrome (hereditary non polyposis colon cancer), hereditary predisposition to colorectal and endometrial adenocarcinomas]

BACKGROUND

The HNPCC syndrome (hereditary nonpolyposis colon cancer) is an inherited condition defined by clinical and genealogical information, known as Amsterdam criteria. In about 70% of cases, HNPCC syndrome is caused by germline mutations in MMR genes, leading to microsatellite instability of tumor DNA (MSI phenotype). Patients affected by the disease are at high risk for colorectal and endometrial carcinomas, but also for small intestine, urothelial, ovary, stomach and biliary tract carcinomas. HNPCC syndrome is responsible for 5% of colorectal cancers. Identification and management of this disease are part of a multidisciplinary procedure.

METHODS

Twelve experts have been mandated by the French Health Ministry to analyze and synthesize their consensus position, and the resulting document has been reviewed by an additional group of 4 independent experts.

MAIN RECOMMENDATIONS

The lack of sensitivity of Amsterdam criteria in recognizing patients carrying a MMR germline mutation led to an enlargement of these criteria for the recruitment of possible HNPCC patients, and to a 2-steps strategy, asking first for a tumor characterization according to MSI phenotype, especially in case of early-onset sporadic cases. The identification of germline MMR mutations has no major consequence on the cancer treatments, but influences markedly the long-term follow-up and the management of at-risk relatives. Gene carriers will enter a follow-up program regarding their colorectal and endometrial cancer risks, but other organs being at low lifetime risk, no specific surveillance will be proposed.

What about chemoprevention for melanoma?

PURPOSE OF REVIEW

This paper aims to critically review the potential for a chemoprevention strategy in melanoma, and to discuss new data on candidate chemoprevention agents, as chemoprevention has been suggested as an unexplored approach in melanoma.

RECENT FINDINGS

A strong scientific rationale, established long-term safety of candidate agents, and a systematic step-wise approach to chemoprevention agent development are all critical for melanoma chemoprevention research. Among potential agents, the lipid-lowering drugs, the statins, satisfy these prerequisites.

SUMMARY

Chemoprevention of cutaneous melanoma can become a valid strategy complementing current prevention approaches, as long as these important prerequisites are taken into consideration.

How should we move the field of chemopreventive agent development forward in a productive manner?

Epidemiologic observations and preclinical experimental investigations suggest that the prevention or reversal of precancers should be an effective strategy in humans to control cancer. Although "proof of principle" has been established in humans, the results of randomized trials have not been confirmatory in most cases. Toxicity in normal or near-normal populations has also been greater than anticipated. We examine the problems associated with testing chemoprevention agents in humans and offer a process and guidelines that may better inform the logical development of this relatively young clinical field.

MF tricyclic and sulindac retard tumor formation in an animal model

New selective cyclooxygenase-2 inhibitors offer the benefit of cancer protection with less gastrointestinal toxicity associated with nonselective nonsteroidal anti-inflammatory drugs (NSAIDs). We hypothesize that MF tricyclic and sulindac can retard all stages of tumor formation in nude mice. In a blinded placebo controlled study, 3 types of experiments were performed: 1) 2.5 x 10(6) cells were injected into 2 flanks of nude mice subcutaneously, as a model for in situ cancer (n = 192); 2) 1 x 10(6) cells were injected into the cecum of mice as a model for in situ colorectal cancer (n = 78) and 3) 0.5 x 10(6) cells were implanted into the splenic subcapsule to establish a colorectal cancer liver metastasis model (n = 78). The animals were fed with standard chow containing either placebo, MF tricyclic (67 mg/kg of chow) or sulindac (150 mg/kg of chow). Mice that were given MF tricyclic or sulindac, at clinical anti-inflammatory plasma concentrations, were significantly more tumor free and had significantly smaller primary tumors and fewer metastases, as compared to mice that consumed placebo. The mortality and the latency period were significantly better in the treatment groups. These findings suggest that selective COX-2 inhibitors may serve as an adjunct to standard therapy in colorectal cancer.

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.

Colorectal cancer prevention

Colorectal cancer is the second leading cause of mortality in the United States. In the United States, the cumulative lifetime risk of developing colorectal cancer for both men and women is 6%. Despite advances in the management of this disease, the 5-year survival rate in the United States in only 62%. Because only 38% of patients are diagnosed when the cancers are localized to the bowel wall, it is likely that widespread implementation of screening could significantly improve the outcome. Colorectal cancer screening is cost effective, irrespective of the methods used. In addition to currently available methods (fecal occult blood, flexible sigmoidoscopy, colonoscopy, and double contrast barium enema), computed tomographic colonography (virtual colonoscopy) and stool-based molecular screening are under development. Four classes of chemopreventive compounds have demonstrated efficacy in reducing recurrent colorectal adenomas and/or cancer in randomized, controlled trials. They are selenium, calcium carbonate, hormone replacement therapy, and nonsteroidal anti-inflammatory drugs. The mechanisms of action of nonsteroidal anti-inflammatory drugs include inhibition of the cyclooxygenase system as well as cyclooxygenase-independent effects. Considerable effort is being expended to define chemopreventive activity, optimal dose, administration schedule, and toxicity for the coxibs in adenoma recurrence prevention trials. The threshold for tolerating toxicities is very low in asymptomatic individuals at minimally increased risk for colorectal neoplasia.

Prevention and therapy of colorectal cancer

Colorectal cancer is expected to affect more than 146,000 and kill more than 57,000 Americans in 2004. Increased understanding of carcinogenesis is transforming clinical approaches to all stages of this disease. During the last 5 years, four new drugs have been approved for colorectal cancer treatment, and substantial progress has been made in identifying and developing agents that prevent or delay carcinogenesis. These advances substantiate target-driven approaches to cancer prevention and treatment, and provide fruitful opportunities for future investigations.