Population Screening for Colorectal Cancer,the Goals and Means

The causes of colorectal cancer are complex and in most cases obscure, making primary prevention impossible at present. Secondary prevention by finding and treating early asymptomatic cancers may possibly reduce mortality from this very common cancer. Results from conventional treatment have changed little during recent decades and are unsatisfactory, with more than half of the patients dying from the disease. The incidence has increased during recent years in many countries, making it vital to evaluate possible benefits from screening.

This review considers different methods of screening for colorectal cancer and includes an overview of continuing European controlled randomised trials with the faecal occult blood test, Haemoccult-ll. No final evaluation is possible, but advantages and drawbacks of different strategies are discussed. Assuming that the goal of reducing mortality is achieved, several other problems remain unsolved: the organisation of screening, the training of doctors in endoscopy, cost benefit and cost effectiveness all of which will have to be solved before a population screening can be recommended. Present screening tools are not ideal and we have to continue the search for better markers of early colorectal cancers and even possible precursors like adenomas.     

Secondary prevention of cancer

OBJECTIVES: To review criteria for mass cancer screening among asymptomatic populations and barriers to secondary prevention of breast, cervical, and colorectal cancers. To describe challenges to implementing theoretically based interventions to increase appropriate cancer screening, follow-up, and surveillance. DATA SOURCES: Published journal articles, text books, and epidemiologic reports. CONCLUSION: Interventions to increase breast, cervical, and colorectal cancer screening participation must be approached from a systems perspective that includes patient, health care provider, and health care system variables. IMPLICATIONS FOR NURSING PRACTICE: Understanding the array of factors that impede progress in the secondary prevention of cancer is necessary to improve care. Nurses have an important role in decreasing morbidity and mortality from breast, cervical, and colorectal cancers.     

Fecal occult blood test screening for colorectal cancer

In summary, high-quality scientific studies indicate that the use of the FOBT for colorectal cancer screening has a number of important advantages. The test is capable of detecting most early colorectal cancers and many advanced adenomas. It has been shown in randomized, controlled trials to reduce substantially colorectal cancer mortality and incidence. The FOBT is feasible, widely available, and acceptable to most individuals. It has a low up-front cost and is highly cost-effective. Combining annual FOBT with periodic flexible sigmoidoscopy seems to be an especially effective screening option. Limitations of FOBT screening include its low sensitivity for polyps, especially smaller ones. Some of the trials report a relatively low sensitivity for detecting cancers located in the distal colon. The test has a relatively low specificity, so there are many false-positive screens; and for it to be most effective, repetitive screening is necessary. Balancing these advantages and disadvantages, the evidence-based screening guidelines have concluded that FOBT screening has a major role to play in colorectal cancer control and a program of annual FOBT plus flexible sigmoidoscopy every 5 years is a preferred option for screening the asymptomatic, average-risk population for colorectal cancer. Short of doing direct colonoscopy screening for the entire at-risk population, the FOBT currently is the best available method of identifying asymptomatic, average-risk people most likely to benefit from colonoscopy.     

Screening of patients at average risk for colon cancer

Both the incidence and the mortality from colorectal cancer can be substantially reduced by primary and secondary prevention. There are many screening tests for colorectal cancer, and any test should result in a reduction in colorectal cancer incidence and mortality. If the age-eligible population undergoes these screening tests, the burden of colorectal cancer should be substantially reduced. The scientific evidence related to secondary prevention, specifically screening of individuals at average risk for colorectal cancer, is presently reviewed.     

Cost of screening for colorectal cancer: results of a community mass screening program and review of the literature.

Colorectal cancer is the second most common form of cancer in the United States, but controversy exists over the feasibility, benefits, and methods of screening. We conducted a large-scale, community-based screening program to determine the cost of screening for colorectal cancer. Based on detailed cost analysis, we arrived at a cost of $15,233 per case of colon cancer diagnosed through mass screening, and $7611 per polyp discovered. These figures are much higher than those previously reported in less detailed studies. Other studies currently under way will determine whether morbidity and mortality are decreased by screening. Our data add the information necessary to determine the cost-effectiveness of mass screening for colon cancer, and will be useful in designing future strategies for the secondary prevention of colorectal cancer.     

Colorectal cancer screening issues: a role for CT colonography?

Colorectal cancer is the third most common cancer in the United States and will cause 56,700 deaths in 2001, despite the availability of screening tests capable of detecting the disease at earlier stages and reducing mortality. This article reviews the natural history of colorectal cancer, common risk factors and prevention strategies, and the strengths, limitations, and cost effectiveness of available screening tests. Although reminders to undergo colorectal cancer screening have become commonplace in the popular media, compliance with screening guidelines remains poor. Although still an unproven technology for widespread screening, computed tomographic (CT) colonography has several attractive characteristics for a screening test. For example, CT scanners are widely available, in contrast to limited numbers of gastroenterologists and radiologists' declining skill and interest in barium enema examinations. Also, patients may be less reluctant to undergo CT colonography than screening colonoscopy. Development of virtual bowel cleansing could further increase compliance and thereby reduce mortality from colorectal cancer. Other articles in this Feature Section discuss technical details of CT colonography and its methodologic challenges.     

Melanoma screening: A plan for improving early detection

Malignant melanoma ranks fifth in the number of new cases annually in the United States (US). Despite increasing incidence and lack of recent improvement in mortality, national melanoma screening guidelines are currently not in existence. Our purpose was to review the evidence regarding screening whole-body skin examinations for early detection and a possible mortality benefit for malignant melanoma. Data sources for our review were MEDLINE Complete, PubMed, Cochrane Library, Cochrane Database of Systematic Reviews, and ClinicalTrials.gov. Study selection included: epidemiologic data from the US and European cancer surveillance registries, population-based case-control screening trials, computer-simulated Markov model trials, and survey trials. Studies were limited to those published in the English language. Data was extracted using a dual extraction method. Data from studies have shown that the mortality of malignant melanoma is highly predicated on the tumor thickness at the time of diagnosis. Our data review is in support of the implementation of whole-body skin examinations, performed by primary care physicians, for the purpose of early detection of melanoma. A large national population-based, case-control, skin cancer screening trial in Germany has shown a reduction in melanoma-specific mortality. In conclusion, our review of the evidence supports physicians performed whole-body skin examination can lead to the detection of earlier stage melanomas as well as to a reduction in disease-specific mortality. We found a paucity of randomized trials to be a limitation of screening studies for many cancers, including melanoma. To improve screening rates and early detection of malignant melanoma, we propose making skin cancer education part of the curriculum in US primary care residency programs to become the genesis for widespread melanoma screening. Our study had no funding.

• Key messages

• Malignant melanoma is the fifth leading cancer in the United States (US).

• In the US and many countries worldwide, the incidence and mortality rates have not declined despite advances seen in the detection and treatment of many cancers.

• Whole-body skin examination is non-invasive and has shown to be cost effective.

• There is evidence supporting a mortality benefit using routine, widespread skin cancer examinations.

• Primary care physicians have been shown to effectively use skin cancer examination for early detection and reduced melanoma mortality.

• The majority of US primary care residents are inadequately trained in skin cancer examination.

• There is a possible survival advantage and cost effectiveness for melanoma screening.

     

Surrogate endpoints for cancer screening trials: general principles and an illustration using the UK Flexible Sigmoidoscopy Screening Trial

Cancer screening is aimed primarily at reducing deaths. Thus, site-specific cancer mortality is the appropriate endpoint for evaluating screening interventions. However, it is also the most demanding endpoint, requiring follow-up and a large numbers of patients order to have adequate power. Therefore, it is highly desirable to have surrogate endpoints that can reliably predict mortality reductions many years earlier. We here review a range of surrogate markers in terms of their potential advantages and pitfalls, and argue that a measure which weights incident cancers according to their predicted mortality has many advantages over other measures and should be used more routinely. Application to the UK Flexible Sigmoidoscopy Screening Trial data suggests that predicted colorectal cancer mortality, based on stage-specific incidence, is a more powerful endpoint than actual mortality and could advance the analysis time by about three years. Total colorectal cancer incidence as a surrogate endpoint provides little advance in the analysis time over actual mortality. The approach requires reliable prognostic data, (e.g. stage), for both the study cohort and a representative sample of the whole population. The routine collection of such data should be a priority for cancer registries. Surrogate endpoints should not replace a long-term analysis based directly on mortality, but can provide reliable early indicators which can be useful both for monitoring ongoing screening programmes and for making policy decisions.     

Recent developments in colorectal cancer screening and prevention

Colorectal cancer is a significant contributor to morbidity and mortality in the United States. Studies published in the early 1990s, showing that screening for colorectal cancer can reduce colorectal cancer-related mortality, led many organizations to recommend screening in asymptomatic, average-risk adults older than 50 years. Since then, however, national screening rates remain low. Several important studies published over the past four years have refined our understanding of existing screening tools and explored novel means of screening and prevention. The most important new developments, which are reviewed in this article, include the following: Additional trial results support the effectiveness of fecal occult blood testing in reducing the incidence of, and mortality from, colorectal cancer. New studies document the sensitivity of fecal occult blood testing, sigmoidoscopy, and double-contrast barium enema compared with colonoscopy. Cost-effectiveness models show that screening by any of several methods is cost-effective compared to no screening. Randomized trials show that calcium is effective but fiber is not effective in preventing reoccurrence of adenomatous polyps. Preliminary data suggest that nonsteroidal anti-inflammatory drugs may prevent adenomatous polyps and that DNA stool tests and virtual colonoscopy may show promise as screening tools. This new information provides further support for efforts to increase the use of colorectal cancer screening and prevention services in adults older than 50 years.     

Primary and secondary prevention of colorectal cancer.

Colorectal cancer is the third leading cause of cancer deaths in the United States. Because of the nature and the progression of the disease, it is highly preventable and suitable for screening. Yet the American Cancer Society estimates included over 100,000 cases of new occurrence of colorectal cancer and over 50,000 deaths in the year 2002. The continued high colorectal cancer mortality rate is due to the under utilization of screening tests.This review will explore the barriers to low screening test use. Implications for healthcare professionals on how to increase the general populations' awareness of colorectal cancer and ways to increase adherence to screening by integrating theories of the Health Belief Model will be discussed. The current research and literature about primary prevention focused on modifiable risk factors and chemoprevention will be examined. Secondary prevention, however, will be the key to help reduce the mortality and morbidity of colorectal cancer. The current screening guidelines will be reviewed as well. It is possible to increase screening rate by modifying and influencing patients' perceived cancer risk, and by educating and training healthcare providers.     

Colonoscopy as a screening test for colorectal cancer in average-risk individuals

Screening for colorectal cancer has become the standard of care and is currently recommended by most major health organizations, including the American Cancer Society. Randomized controlled trials using fecal occult blood testing as the screening strategy have shown a reduction in mortality due to colorectal cancer. However, colorectal cancer differs from other cancers in that a variety of screening tests have been approved and recommended by experts. The advantages and disadvantages of different screening tests have been the subject of intense debate. Colonoscopy has theoretical advantages over other screening tests, including direct visualization of the entire colon and, more importantly, removal of precancerous adenomatous lesions. This review discusses the advantages and disadvantages of colonoscopy as a screening test for colorectal cancer with regard to efficacy, cost-effectiveness, and patient compliance.     

Colorectal cancer: risk factors and recommendations for early detection.

Spurred by mounting evidence that the detection and treatment of early-stage colorectal cancers and adenomatous polyps can reduce mortality, Medicare and some other payors recently authorized reimbursement for colorectal cancer screening in persons at average risk for this malignancy. A collaborative group of experts convened by the U.S. Agency for Health Care Policy and Research has recommended screening for average-risk persons over the age of 50 years using one of the following techniques: fecal occult blood testing each year, flexible sigmoidoscopy every five years, fecal occult blood testing every year combined with flexible sigmoidoscopy every five years, double-contrast barium enema every five to 10 years or colonoscopy every 10 years. Screening of persons with risk factors should begin at an earlier age, depending on the family history of colorectal cancer or polyps. These recommendations augment the colorectal cancer screening guidelines of the American Academy of Family physicians. Recent advances in genetic research have made it possible to identify persons at high risk for colorectal cancer because of an inherited predisposition to develop this malignancy. These patients require aggressive screening, usually by lower endoscopy performed at an early age. In some patients, genetic testing can guide screening and may be cost-effective.     

Colorectal cancer screening: an overview of current trends

Colorectal cancer can be cured and, in some cases, even prevented if detected early through screening. Studies have demonstrated that regular screening for colorectal cancer with fecal occult blood testing, sigmoidoscopy, or colonoscopy can reduce mortality from this disease. Unfortunately, rates of participation in these screening tests are unacceptably low among the U.S. population. Nurses have a significant role to play in assisting individuals to incorporate regular colorectal cancer screening into their health maintenance routines.     

Prevention of colon cancer in primary care practice

Colorectal cancer is a common disease with a high mortality rate. Surgical resection in early stages is the only effective treatment, therefore, recent attention is focused on diagnosing early colon cancer by screening asymptomatic subjects. Principles and current technology supporting early detection of colorectal cancer are critically evaluated. Current guidelines for screening average risk asymptomatic subjects and high-risk groups are discussed.     

Screening for colorectal cancer in a Hungarian county

An initial screening for colorectal cancer in asymptomatic adults was performed with Haemoccult in 26,357 persons, rigid rectoscopy in 10,673 and flexible sigmoidoscopy in 3,963 persons. The rate of cancer detection was 4.4% in screenees with a positive Haemoccult test, 0.08% using rigid rectoscopy and 0.28% using flexible sigmoidoscopy. The respective frequency of patients discovered to have polyps was 16.2%, 1.32% and 8.49%. 77% of the 36 colorectal cancers detected due to the Haemoccult test program were either Dukes A or B. A comparison of these screening results indicates that Haemoccult screening markedly increases the yield of colorectal neoplasms when asymptomatic persons are examined. This screening should be repeated annually to reduce the morbidity and mortality of colorectal cancer.     

Cancer prevention and early detection

Advances in the area of cancer prevention and early detection are being made constantly. Basic epidemiologic research continues to provide insight into the impact of carcinogen exposure and the development of cancer. It is exciting to note that the study of Tamoxifen and Raloxifene chemoprevention trial is successfully recruiting women, including minority women, to participate. This large chemoprevention trial is providing much insight into how to recruit and retain women to take a chemoprevention agent to ultimately prevent the development of cancer. Advances also are being made in the knowledge base of how to best detect cancer in asymptomatic people. The best screening tool recommendation for the early detection of colorectal cancer remains controversial. Screening for colorectal cancer, however, is the only way to ultimately decrease the morbidity and mortality associated with the disease. Oncology nurses need to accurately risk for colorectal cancer and provide patients with the necessary information to make an informed choice about the most appropriate screening for their situation. Oncology nurses need to be familiar with new research and advances in cancer prevention and early detection so they can share information with patients and their families.     

Testicular, prostate and penile cancers in primary care settings: the importance of early detection.

Male testicular, prostate and penile cancers will be responsible for 32,625 deaths in 1991. Fortunately, prevention and early detection of cancer can decrease mortality and morbidity. Armed with knowledge of the incidence of testicular, prostate and penile cancers, risk factors, and clinical presentations, the clinician will be better able to implement primary and secondary prevention. Recommended screening schedules are reviewed in this article, and suggestions for assessment, differential diagnosis and practice are discussed.     

Ovarian cancer strategies for nurse practitioners

PURPOSE: To review and outline practical strategies for the effective detection and prevention of ovarian cancer. DATA SOURCES: Selected scientific literature, government consensus findings, and the author's experience. CONCLUSIONS: Ovarian cancer is the fourth most common cause of cancer death in American women, ranking behind lung, breast, and colorectal cancer. Seventy-five percent of ovarian cancers are currently diagnosed at an advanced stage. IMPLICATIONS FOR PRACTICE: No cost-effective screening methods are currently available. The battle to beat ovarian cancer is based on four strategies: identification of risk factors, appropriate screening methods, early detection, and prevention.     

Gastrointestinal malignancies

Gastrointestinal cancers are collectively the most common malignancies in the world. In the United States, colorectal cancer accounts for most of these malignancies. This is unfortunate, because colorectal cancer is highly preventable. Moreover, screening for colorectal cancer is cost effective and becomes increasingly important in an aging population. Individuals who are more at risk require earlier screening and intervention. For all gastrointestinal cancer, surgery remains the most important curative option. For patients who cannot be cured, quality of life is the yardstick by which palliative options should be evaluated.     

Colorectal cancer screening: an overview of available methods and current recommendations

BACKGROUND: Screening asymptomatic persons for colorectal cancer may decrease the incidence and mortality of this disease. METHODS: The MEDLINE database was used to identify articles addressing the rationale for colorectal cancer screening, methods used and their effectiveness, and current recommendations. RESULTS: Methods of screening for colorectal cancer include flexible sigmoidoscopy, fecal occult blood tests, barium enema, and colonoscopy. The method used and the frequency of screening are determined by assessing an individual's risk of having colorectal cancer. CONCLUSIONS: Colorectal cancer is a common malignancy in the United States, is curable when detected at an early stage, and is potentially preventable. The acceptance of colorectal cancer screening by patients and physicians has been suboptimal. while there remains little debate about the potential for screening to reduce mortality from colorectal cancer, debate continues about the cost-effectiveness of colorectal cancer screening when applied to the general population.