***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: Despite recent declines in both incidence and mortality ( 1 ) , colorectal cancer remains the second most common cause of death from cancer in the United States ( 2 ) . Screening for colorectal cancer reduces mortality by allowing physicians to detect cancer at earlier , more treatable stages , as well as to identify and remove adenomatous polyps ( asymptomatic benign precursor lesions that may lead to colorectal cancer ) . Many tests are available for screening , such as fecal occult blood tests ( FOBTs ) , flexible sigmoidoscopy , and colonoscopy . Screening with FOBT ( Hemoccult II , Beckman Coulter , Fullerton , California ) has been shown to reduce colorectal cancer mortality by 15 % to 33 % in r and omized , controlled trials ( 35 ) , and screening with more sensitive FOBTs , flexible sigmoidoscopy , colonoscopy , or combinations of these tests may reduce the burden of colorectal cancer even more ( 6 , 7 ) . In the absence of adequate clinical trial data on several recommended screening strategies , microsimulation modeling can provide guidance on the risks , benefits , and testing re sources required for different screening strategies to reduce the burden of colorectal cancer . In July 2002 , the U.S. Preventive Services Task Force ( USPSTF ) concluded that there was sufficient evidence to recommend strongly that all average-risk adults 50 years of age or older should be offered colorectal cancer screening ( 8) . However , the logistics of screening , such as the type of screening test , screening interval , and age at which to stop screening , were not evaluated in terms of the balance of benefits and potential harms . The USPSTF has again addressed recommendations for colorectal cancer screening with a systematic review of the evidence ( 9 ) on screening tests . For this assessment , the USPSTF requested a decision analysis to project expected outcomes of various strategies for colorectal cancer screening . Two independent microsimulation modeling groups from the Cancer Intervention and Surveillance Modeling Network ( CISNET ) , funded by the National Cancer Institute , used a comparative modeling approach to compare life-years gained relative to re source use of different strategies for colorectal cancer screening . Methods We used 2 microsimulation models  , MISCAN ( MIcrosimulation Screening Analysis ) ( 1012 ) and SimCRC ( Simulation Model of Colorectal Cancer ) ( 13 ) , to estimate the life-years gained relative to no screening and the colonoscopies required ( that is , an indicator for re source use and risk for complications ) for different colorectal cancer screening strategies defined by test , age at which to begin screening , age at which to stop screening , and screening interval . We aim ed to identify a set of recommendable strategies with similar clinical benefit and an efficient use of colonoscopy re sources . Using 2 models ( that is , a comparative modeling approach ) adds credibility to the results and serves as a sensitivity analysis on the underlying structural assumptions of the models , particularly pertaining to the unobservable natural history of colorectal cancer . Microsimulation Models The Appendix describes the MISCAN and SimCRC models , and st and ardized model profiles are available at cisnet.cancer.gov/profiles/. In brief , both models simulate the life histories of a large population of individuals from birth to death . As each individual ages , there is a chance that an adenoma will develop . One or more adenomas can occur in an individual , and each adenoma can independently develop into pre clinical ( that is , undiagnosed ) colorectal cancer ( Figure 1 ) . The risk for developing an adenoma depends on age , sex , and baseline individual risk . The models track the location and size of each adenoma ; these characteristics influence disease progression and the chance that the adenoma will be found by screening . The size of adenomas can progress from small ( 5 mm ) to medium ( 6 to 9 mm ) to large ( 10 mm ) . Some adenomas eventually become malignant , transforming to stage I pre clinical cancer . Pre clinical cancer has a chance of progressing through stages I to IV and may be diagnosed by symptoms at any stage . Survivorship after diagnosis depends on the stage of disease . Figure 1 . Natural history of disease as modeled by the Microsimulation Screening Analysis and Simulation Model of Colorectal Cancer models . The opportunity to intervene in the natural history through screening is noted . The natural history component of each model was calibrated to 19751979 clinical incidence data ( 14 ) and adenoma prevalence from autopsy studies in the same period ( 1524 ) . We used this period because incidence rates and adenoma prevalence had not yet been affected by screening . We corrected the adenoma prevalence for studies of non-U.S. population s by using st and ardized colorectal cancer incidence ratios . The models use all-cause mortality estimates from the U.S. life tables and stage-specific data on colorectal cancer survival from the 19961999 Surveillance , Epidemiology , and End Results program ( 14 ) . Table 1 compares outcomes from the natural history components of the models . Table 1 . Comparison of the Natural History Outcomes from the Microsimulation Screening Analysis ( MISCAN ) and Simulation Model of Colorectal Cancer ( SimCRC ) Models The effectiveness of a screening strategy is modeled through a test 's ability to detect lesions ( that is , adenomas or pre clinical cancer ) . Once screening is introduced , a simulated person who has an underlying lesion has a chance of having it detected during a screening round depending on the sensitivity of the test for that lesion and whether the lesion is within the reach of the test . Screened persons without an underlying lesion can have a false-positive test result and undergo unnecessary follow-up colonoscopy . Hyperplastic polyps are not modeled explicitly , but their detection is reflected in the specificity of the screening tests . The models incorporate the risk for fatal complications associated with perforation during colonoscopy . Both models have been vali date d against the long-term reductions in incidence and mortality of colorectal cancer with annual FOBT reported in the Minnesota Colon Cancer Control Study ( 3 , 25 , 26 ) and show good concordance with the trial results . Strategies for Colorectal Cancer Screening In consultation with the USPSTF , we included the following basic strategies : 1 ) no screening , 2 ) colonoscopy , 3 ) FOBT ( Hemoccult II , Hemoccult SENSA [ Beckman Coulter ] , or fecal immunochemical testing ) , 4 ) flexible sigmoidoscopy ( with biopsy ) , and 5 ) flexible sigmoidoscopy combined with Hemoccult SENSA . For each basic strategy , we evaluated start ages of 40 , 50 , and 60 years and stop ages of 75 and 85 years . For the FOBT strategies , we considered screening intervals of 1 , 2 , and 3 years , and for the sigmoidoscopy and colonoscopy strategies , we considered intervals of 5 , 10 , and 20 years . These variations result ed in 145 strategies : 90 single-test strategies , 54 combination-test strategies , and 1 no-screening strategy . The stop age reflects the oldest possible age at which to screen , but the actual stopping age is dictated by the start age and screening interval . In the base case , we assumed 100 % adherence for screening tests , follow-up of positive findings , and surveillance of persons found to have adenomas . Individuals with a positive FOBT result or with an adenoma detected by sigmoidoscopy were referred for follow-up colonoscopy . For years in which both tests were due for the combined strategy , the FOBT was performed first ; if the result was positive , the patient was referred for follow-up colonoscopy . In those years , flexible sigmoidoscopy was done only for patients with a negative FOBT result . If findings on follow-up colonoscopy were negative , the individual was assumed to undergo subsequent screening with colonoscopy with a 10-year interval ( as long as results of the repeated colonoscopy were negative ) and did not return to the initial screening schedule , as is the recommendation of the U.S. Multi-Society Task Force and American Cancer Society ( 7 , 27 ) . All individuals with an adenoma detected were followed with colonoscopy surveillance per the Multi-Society guidelines ( 27 , 28 ) . The surveillance interval depended on the number and size of the adenomas detected on the last colonoscopy ; it ranged from 3 to 5 years and was assumed to continue for the remainder of the person 's lifetime . We estimated the test characteristics of colorectal cancer screening from a review of the available literature ( Table 2 ) ( 29 ) . We conducted this review independently of and parallel in time with the systematic evidence review performed for the USPSTF ( 9 ) . Table 2 . Test Characteristics Used in the Microsimulation Screening Analysis and Simulation Model of Colorectal Cancer Models Evaluation of Outcomes Determination of Efficient Strategies The most effective strategy was defined as the one with the greatest life-years gained relative to no screening . However , it is important to consider the relative intensity of test use required to achieve those gains . The more effective strategies tended to be associated with more colonoscopies on average in a person 's lifetime , which translated into an increased risk for colonoscopy-related complications . We used an approach that mirrors that of cost-effectiveness analysis ( 30 ) to identify the set of efficient , or dominant , strategies within each test category . A strategy was considered dominant when no other strategy or combination of strategies provided more life-years with the same number of colonoscopies . We conducted this analysis separately for each of the 5 basic screening strategies because the number of noncolonoscopy tests differed by strategy . We then ranked the efficient screening strategies by increasing effectiveness and calculated the incremental number of colonoscopies ( COL ) per 1000 , the incremental life-years gained ( LYG ) per 1000 , and the incremental number of colonoscopies necessary to achieve 1 year of life ( Objective : This is the first study to evaluate the association between colonic screening and  colorectal cancer risk among Canadians . Methods : A case – control study was conducted . Cases were diagnosed with cancer of the colorectum , between 1997 and 2000 , aged 20 to 74 years , identified through the population -based Ontario Cancer Registry and recruited by the Ontario Familial Colorectal Cancer Registry . Controls were a sex- and age-matched r and om sample of the population of Ontario . 971 cases and 1944 controls completed question naires ( including colorectal screening history and many risk factors ) . Multivariate logistic regression analysis was used to obtain adjusted odds ratios ( OR ) estimates . Results : Having had a fecal occult blood screen was associated with reduced colorectal cancer risk ( OR=0.76 ; 95 % confidence interval ( CI ) : 0.59 , 0.97 ) . Having had a screening sigmoidoscopy was associated with a halving of colorectal cancer risk ( OR = 0.52 ; 95 % CI : 0.34 , 0.80 ) . Having had a screening colonoscopy did not significantly reduce colorectal cancer risk ( OR = 0.69 ; 95 % CI : 0.44 , 1.07 ) ; however , having had either screening endoscopy was associated with a significant reduction in colorectal cancer risk ( OR = 0.62 ; 95 % CI : 0.44 , 0.87 ) . Findings differed slightly by anatomic sub-site ( proximal and distal colorectum ) . Conclusions : We report a reduction in colorectal cancer risk  among persons who underwent colorectal cancer screening ; in particular , sigmoidoscopy . Findings are of great importance for the prevention of colorectal cancer OBJECTIVES We compared the effectiveness of a telephone outreach approach versus a direct mail approach in improving rates of colorectal cancer ( CRC ) screening in a predominantly Black population . METHODS A r and omized trial was conducted between 2000 and 2003 that followed 456 participants in the New York metropolitan area who had not had recent CRC screening . The intervention group received tailored telephone outreach , and the control group received mailed printed material s. The primary outcome was medically documented CRC screening 6 months or less after r and omization . RESULTS CRC screening was documented in 61 of 226 ( 27.0 % ) intervention participants and in 14 of 230 ( 6.1 % ) controls ( prevalence rate difference=20.9 % ; 95 % CI = 14.34 , 27.46 ) . Compared with the control group , the intervention group was 4.4 times more likely to receive CRC screening within 6 months of r and omization . CONCLUSIONS Tailored telephone outreach can increase CRC screening in an urban minority population BACKGROUND : National guidelines recommending colorectal cancer ( CRC ) screening for average risk Canadians were released in 2001 . The current study determined rates of CRC screening and predictors of screening 3 yr after the guidelines were released . METHOD : A population -based r and om digit dial telephone survey of 1,808 Alberta men and women aged 50–74 yr assessed awareness about , and self-reported rates of , screening . RESULTS : More average risk women than men reported a recent  screening  with a home fecal occult blood test ( FOBT ) ( 14.0 % vs 9.8 % , P = 0.013 ) but men had slightly higher rates of screening endoscopy in the past 5 yr ( 4.3 % vs 1.6 % , P = 0.003 ) . Overall , only 14.3 % of average risk adults ( N = 1,476 ) were up-to- date on 
    Output:
    
Analysis of national survey data showed higher prevalences among men aged 55 years and older than for women of the same age .
Prevalences were highest for people aged 70 to 79 years .
Prevalence estimates from the United States indicate that a considerable and increasing proportion of the population at risk has had at least 1  colonoscopy or sigmoidoscopy  in their lives , although differences between age and sex groups persist .