***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: BACKGROUND Screening for colorectal cancer is widely recommended , but the preferred strategy remains unidentified . We aim ed to compare participation and diagnostic yield between screening with colonoscopy and with non-cathartic CT colonography . METHODS Members of the general population , aged 50 - 75 years , and living in the regions of Amsterdam or Rotterdam , identified via the registries of the regional municipal administration , were r and omly allocated ( 2:1 ) to be invited for primary screening  for colorectal cancer by colonoscopy or by CT colonography . R and omisation was done per household with a minimisation algorithm based on age , sex , and socioeconomic status . Invitations were sent between June 8 , 2009 , and Aug 16 , 2010 . Participants assigned to CT colonography who were found to have one or more large lesions ( ≥10 mm ) were offered colonoscopy ; those with 6 - 9 mm lesions were offered surveillance CT colonography . The primary outcome was the participation rate , defined as number of invitees undergoing the examination relative to the total number of invitees . Diagnostic yield was calculated as number of participants with advanced neoplasia relative to the total number of invitees . Invitees and screening centre employees were not masked to allocation . This trial is registered in the Dutch trial register , number NTR1829 . FINDINGS 1276 ( 22 % ) of 5924 colonoscopy invitees participated , compared with 982 ( 34 % ) of 2920 CT colonography invitees ( relative risk [ RR ] 1·56 , 95 % CI 1·46 - 1·68 ; p<0·0001 ) . Of the participants in the colonoscopy group , 111 ( 9 % ) had advanced neoplasia of whom seven ( < 1 % ) had a carcinoma . Of CT colonography participants , 84 ( 9 % ) were offered colonoscopy , of whom 60 ( 6 % ) had advanced neoplasia of whom five ( < 1 % ) had a carcinoma ; 82 ( 8 % ) were offered surveillance . The diagnostic yield for all advanced neoplasia was 8·7 per 100 participants for colonoscopy versus 6·1 per 100 for CT colonography ( RR 1·46 , 95 % CI 1·06 - 2·03 ; p=0·02 ) and 1·9 per 100 invitees for colonoscopy and 2·1 per 100 invitees for CT colonography ( RR 0·91 , 0·66 - 2·03 ; p=0·56 ) . The diagnostic yield for advanced neoplasia of 10 mm or more was 1·5 per 100 invitees for colonoscopy and 2·0 per 100 invitees for CT colonography , respectively ( RR 0·74 , 95 % CI 0·53 - 1·03 ; p=0·07 ) . Serious adverse events related to the screening procedure were post-polypectomy bleedings : two in the colonoscopy group and three in the CT colonography group . INTERPRETATION Participation in colorectal cancer screening with CT colonography was significantly better than with colonoscopy , but colonoscopy identified significantly more advanced neoplasia per 100 participants than did CT colonography .  The diagnostic yield for advanced neoplasia per 100 invitees was similar for both strategies , indicating that both techniques can be used for population -based screening for colorectal cancer . Other factors such as cost-effectiveness and perceived burden should be taken into account when deciding which technique is preferable . FUNDING Netherl and s Organisation for Health Research and Development , Centre for Translational Molecular Medicine , and the Nuts Ohra Foundation BACKGROUND & AIMS Data from r and omized controlled trials on the effects of screening colonoscopies on colorectal cancer ( CRC ) incidence and mortality are not available . Observational studies have suggested that colonoscopies strongly reduce the risk of CRC , but there is little specific evidence on the effects of screening colonoscopies . METHODS We performed a population -based case-control study of 3148 patients with a first diagnosis of CRC ( cases ) and 3274 subjects without CRC ( controls ) from the Rhine-Neckar region of Germany from 2003 to 2010 . Detailed information on previous colonoscopy and potential confounding factors was collected by st and ardized personal interviews . Self-reported information on colonoscopies and their indications was vali date d by medical records . We used multiple logistic regression to assess the association between colonoscopy conducted for specific indications within the past 10 years and risk of CRC . RESULTS A history of colonoscopy was associated with a reduced subsequent risk of CRC , independently of the indication for the examination . However , somewhat stronger associations were found for examinations with screening indications ( adjusted odds ratio [ OR ] 0.09 , 95 % confidence interval [ CI ] 0.07 - 0.13 ) than for examinations with diagnostic indications , such as positive fecal occult blood test result ( OR , 0.33 ; 95 % CI , 0.19 - 0.57 ) , surveillance after a preceding colonoscopy ( OR , 0.33 ; 95 % CI , 0.24 - 0.45 ) , rectal bleeding ( OR , 0.28 ; 95 % CI , 0.20 - 0.40 ) , abdominal symptoms ( OR , 0.15 ; 95 % CI , 0.10 - 0.21 ) , or other ( OR , 0.21 ; 95 % CI , 0.14 - 0.30 ) . Colonoscopy was also associated with a reduced risk of cancer in the right colon , regardless of the indication , although to a smaller extent than for other areas of the colon ( OR for screening colonoscopy , 0.22 ; 95 % CI , 0.14 - 0.33 ) . CONCLUSIONS In a population -based case-control study , the risk of CRC was strongly reduced up to 10 years after colonoscopy for any indication . Risk was particularly low after screening colonoscopy , even for cancer in the right colon BACKGROUND In r and omized trials , fecal occult-blood testing reduces mortality from colorectal cancer . However , the duration of the benefit is unknown , as are the effects specific to age and sex . METHODS In the Minnesota Colon Cancer Control Study , 46,551 participants , 50 to 80 years of age , were r and omly assigned to usual care ( control ) or to annual or biennial screening with fecal occult-blood testing . Screening was performed from 1976 through 1982 and from 1986 through 1992 . We used the National Death Index to obtain up date d information on the vital status of participants and to determine causes of death through 2008 . RESULTS Through 30 years of follow-up , 33,020 participants ( 70.9 % ) died . A total of 732 deaths were attributed to colorectal cancer : 200 of the 11,072 deaths ( 1.8 % ) in the annual-screening group , 237 of the 11,004 deaths ( 2.2 % ) in the biennial-screening group , and 295 of the 10,944 deaths ( 2.7 % ) in the control group . Screening reduced colorectal-cancer mortality ( relative risk with annual screening , 0.68 ; 95 % confidence interval [ CI ] , 0.56 to 0.82 ; relative risk with biennial screening , 0.78 ; 95 % CI , 0.65 to 0.93 ) through 30 years of follow-up . No reduction was observed in all-cause mortality ( relative risk with annual screening , 1.00 ; 95 % CI , 0.99 to 1.01 ; relative risk with biennial screening , 0.99 ; 95 % CI , 0.98 to 1.01 ) . The reduction in colorectal-cancer mortality was larger for men than for women in the biennial-screening group ( P=0.04 for interaction ) . CONCLUSIONS The effect of screening with fecal occult-blood testing on colorectal-cancer mortality persists after 30 years but does not influence all-cause mortality . The sustained reduction in colorectal-cancer mortality supports the effect of polypectomy . ( Funded by the Veterans Affairs Merit Review Award Program and others . ) Introduction : We conducted a cluster-r and omized trial aim ed at assessing the effect of the type of faecal occult blood , guaiac or immunochemical test on screening compliance . Methods : We sample d 130 general practitioners ( GPs ) who consented to participate in the trial . We r and omly allocated half of them to the guaiac ( Hemo-Fec ) and half to the immunochemical test ( OC-Hemodia ) . We sample d 2/10 of the GPs ' 50–75-year-old patients ( n=7332 ) and r and omly divided this population into half . One half was invited to be screened at the GP 's office and the other to the nearest gastroenterology ward . The principal outcome was the percentage of returned tests . Results : The immunochemical test had a compliance of 35.8 % and the guaiac of 30.4 % ( relative risk [ RR ] 1.20 ; 95 % confidence interval [ CI ] 1.02–1.44 ) . The difference was mostly due to a higher probability of returning the sample : 93.8 % and 88.6 % for immunochemical and guaiac , respectively ( RR 1.06 ; 95 % CI 1.02–1.10 ) . The guaiac test had a higher prevalence of positives ( 10.3 % versus 6.3 % , RR 0.603 ; 95 % CI 0.433–0.837 ) . There was a higher variability in the results obtained with the guaiac test compared with the immunochemical ( F[1 , 12 ] = 16.25 ; P=0.0017 ) . Conclusions : Compliance is more likely with the immunochemical than the guaiac test , independent of the provider . Guaiac tests show a higher variability of the results among centres . The successful implementation of a screening programme requires a period of st and ardization of the test reading in order to avoid unexpected work overload for colonscopy services BACKGROUND Data on the adherence rate to screening colonoscopy ( OC ) in the average-risk general population are limited and variable . Aim of this study was to compare the uptake of OC screening with that of fecal occult blood ( FOBT ) . METHODS A nationwide , population -based , multicentre , r and omized trial comparing attendance to OC with that to FOBT was performed . Sixty-four general practitioners ( GPs ) , overall including in their lists 9889 average-risk subjects aged 55 - 64 years , were r and omized between OC and FOBT screening programs .  Eligible subjects were mailed a personal invitation letter co-signed by their GP and the coordinator of the area-reference GI centre . Attendance rate and detection rate for advanced neoplasia ( colorectal cancer , adenoma > 10 mm or with villous histology or high- grade dysplasia ) for each arm of the study were assessed . RESULTS The overall attendance rate was 18.7 % ( 1563/8378 eligible subjects ) . It was markedly lower in the OC than in the FOBT strategy ( 10 % vs. 27.1 % ; OR 0.28 , 95 % CI : 0.25 - 0.32 ; P<0.0001 ) . In particular , participation in OC screening  arm was extremely low in South Italy ( 2.8 % ) , whilst it was higher in North- Central Italy ( 12.4 % ; P<0.0001 ) . Compliance to colonoscopy  in those with a positive FOBT was only 58 % . Advanced neoplasia was detected in 28 ( 6.8 % ) patients in the OC arm and in 6 ( 18 % ) in those with a positive FOBT su bmi tted to OC . CONCLUSIONS The results of our study underline the difficulties and barriers to implement a OC population screening in Italy , at least through primary care . Although attendance to FOBT was higher , it was disappointingly less than 30 % . Significant actions to improve awareness amongst GPs and the population are a high priority BACKGROUND : The role of screening colonoscopy for colorectal ( CR ) neoplasia in average-risk population , remains to be determined . OBJECTIVES : To evaluate the prevalence and anatomic location of CR adenoma and carcinoma and the morbidity of colonoscopy  in individuals at average risk for CR cancer ( CRC ) . METHODS : A retrospective prevalence study of subjects aged 40–80 yr , with no cancer-related symptoms , personal or family history of CR neoplasia , who underwent a colonoscopy .  RESULTS : Enrolled were 1,177 persons ; 183 aged 40–49 yr ( young ) , 917 aged 50–75 yr , and 77 aged 76–80 yr ( elderly ) . The prevalence of overall CR neoplasia , advanced neoplasia , and cancer was 20.9 % , 6.3 % , and 1.1 % , respectively . In the 50–75 age group , the prevalence of overall adenoma , advanced ne 
    Output:
    
Flexible sigmoidoscopy ( FS ) prevented CRC and led to the largest reduction in CRC mortality with a smaller but significant reduction in CRC mortality with the use of guaiac fecal occult blood tests ( gFOBTs ) .
There was insufficient or low quality evidence to support the use of other screening tests , including colonoscopy , as well as changing the ages of initiation and cessation for CRC screening with gFOBTs in Ontario .
Either annual or biennial screening using gFOBT reduces CRC-related mortality .
Conclusion .
The evidentiary base supports the use of FS or FOBT ( either annual or biennial ) to screen patients at average risk for CRC .