***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 & 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 AND STUDY AIM While colonoscopy screening is widely used in several European countries and the United States , there are no r and omized trials to quantify its benefits . The Nordic-European Initiative on Colorectal Cancer ( NordICC ) is a multinational , r and omized controlled trial aim ing at investigating the effect of colonoscopy screening on colorectal cancer ( CRC ) incidence and mortality . This paper describes the rationale and design of the NordICC trial . STUDY DESIGN Men and women aged 55 to 64 years are drawn from the population registries in the participating countries and r and omly assigned to either once-only colonoscopy screening with removal of all detected lesions , or no screening ( st and ard of care in the trial regions ) . All individuals are followed for 15 years after inclusion using dedicated national registries . The primary end points of the trial are cumulative CRC-specific death and CRC incidence during 15 years of follow-up . POWER ANALYSIS : We hypothesize a 50 % CRC mortality-reducing efficacy of the colonoscopy intervention and predict 50 % compliance , yielding a 25 % mortality reduction among those invited to screening . For 90 % power and a two-sided alpha level of 0.05 , using a 2:1 r and omization , 45 600 individuals will be r and omized to control , and 22 800 individuals to the colonoscopy group . Interim analyses of the effect of colonoscopy on CRC incidence and mortality will be performed at 10-year follow-up . CONCLUSIONS The aim of the NordICC trial is to quantify the effectiveness of population -based colonoscopy screening .  This will allow development of evidence -based guidelines for CRC screening in the general population 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 BACKGROUND A single flexible sigmoidoscopy at around the age of 60 years has been proposed as an effective strategy for colorectal cancer ( CRC ) screening . METHODS We conducted a r and omized controlled trial to evaluate the effect of flexible sigmoidoscopy screening on CRC incidence and mortality . A question naire to assess the eligibility and interest in screening was mailed to 236,568 men and women , aged 55 - 64 years , who were r and omly selected from six trial centers in Italy . Of the 56,532 respondents , interested and eligible subjects were r and omly assigned to the intervention group ( invitation for flexible sigmoidoscopy ; n = 17,148 ) or the control group ( no further contact ; n = 17,144 ) , between June 14 , 1995 , and May 10 , 1999 .  Flexible sigmoidoscopy was performed on 9911 subjects . Intention-to-treat and per- protocol analyses were performed to compare the CRC incidence and mortality rates in the intervention and control groups . Per- protocol analysis was adjusted for noncompliance . RESULTS A total of 34,272 subjects ( 17,136 in each group ) were included in the follow-up analysis . The median follow-up period was 10.5 years for incidence and 11.4 years for mortality ; 251 subjects were diagnosed with CRC in the intervention group and 306 in the control group . Overall incidence rates in the intervention and control groups were 144.11 and 176.43 , respectively , per 100,000 person-years . CRC-related death was noted in 65 subjects in the intervention group and 83 subjects in the control group . Mortality rates in the intervention and control groups were 34.66 and 44.45 , respectively , per 100,000 person-years . In the intention-to-treat analysis , the rate of CRC incidence was statistically significantly reduced in the intervention group by 18 % ( rate ratio [ RR ] = 0.82 , 95 % confidence interval [ CI ] = 0.69 to 0.96 ) , and the mortality rate was non-statistically significantly reduced by 22 % ( RR = 0.78 ; 95 % CI = 0.56 to 1.08 ) compared with the control group . In the per- protocol analysis , both CRC incidence and mortality rates were statistically significantly reduced among the screened subjects ; CRC incidence was reduced by 31 % ( RR = 0.69 ; 95 % CI = 0.56 to 0.86 ) and mortality was reduced by 38 % ( RR = 0.62 ; 95 % CI = 0.40 to 0.96 ) compared with the control group . CONCLUSION A single flexible sigmoidoscopy screening between ages 55 and 64 years was associated with a substantial reduction of CRC incidence and mortality OBJECTIVES : Fecal occult blood testing ( FOBT ) and sigmoidoscopy are proven to decrease colorectal cancer ( CRC ) incidence and mortality . Sigmoidoscopy 's benefit is limited to the distal colon . Observational data are conflicting regarding the degree to which colonoscopy affords protection against proximal CRC . Our aim was to explore the comparative effectiveness and cost-effectiveness of colonoscopy vs. sigmoidoscopy and alternative CRC screening strategies in light of the latest published data . METHODS : We performed a contemporary cost-utility analysis using a Markov model vali date d against data from r and omized controlled trials of FOBT and sigmoidoscopy .  Persons at average CRC risk within the general US population were modeled . Screening strategies included those recommended by the United States ( US ) Preventive Services Task Force , including colonoscopy every 10 years ( COLO ) , flexible sigmoidoscopy every 5 years ( FS ) , annual fecal occult blood testing , annual fecal immunochemical testing ( FIT ) , and the combination FS/FIT . The main outcome measures were quality -adjusted life-years ( QALYs ) and costs . RESULTS : In the base case , FIT dominated other strategies . The advantage of FIT over FS and COLO was contingent on rates of uptake and adherence that are well above current US rates . Compared with FIT , FS and COLO both cost < $ 50,000/QALY gained when FIT per-cycle adherence was < 50 % . COLO cost $ 56,800/QALY gained vs. FS in the base case . COLO cost < $ 100,000/QALY gained vs. FS when COLO yielded a relative risk of proximal CRC of < 0.5 vs. no screening . In probabilistic analyses , COLO was cost-effective vs. FS at a willingness-to-pay threshold of $ 100,000/QALY gained in 84 % of iterations . CONCLUSIONS : Screening colonoscopy may be cost-effective compared with FIT and sigmoidoscopy , depending on the relative rates of screening uptake and adherence and the protective benefit of colonoscopy in the proximal colon . Colonoscopy 's cost-effectiveness compared with sigmoidoscopy is contingent on the ability to deliver ∼50 % protection against CRC in the proximal colon IMPORTANCE Deep sedation for endoscopic procedures has become an increasingly used option but , because of impairment in patient response , this technique also has the potential for a greater likelihood of adverse events . The incidence of these complications has not been well studied at a population level . DESIGN Population -based study . SETTING AND PARTICIPANTS Using a 5 % r and om sample of cancer-free Medicare beneficiaries who resided in one of the regions served by a SEER ( Surveillance , Epidemiology , and End Results ) registry , we identified all procedural cl aims for outpatient colonoscopy without polypectomy from January 1 , 2000 , through November 30 , 2009 . INTERVENTION Colonoscopy without polypectomy , with or without the use of deep sedation ( identified by a concurrent cl aim for anesthesia services ) . MAIN OUTCOME MEASURES The occurrence of hospitalizations for splenic rupture or trauma , colonic perforation , and aspiration pneumonia within 30 days of the colonoscopy . RESULTS We identified a total of 165 527 procedures in 100 359 patients , including 35 128 procedures with anesthesia services ( 21.2 % ) . Selected postprocedure complications were documented after 284 procedures ( 0.17 % ) and included aspiration ( n = 173 ) , perforation ( n = 101 ) , and splenic injury ( n = 12 ) . ( Some patients had > 1 complication . ) Overall complications were more common in cases with anesthesia assistance ( 0.22 % [ 95 % CI , 0.18%-0.27 % ] ) than in others ( 0.16 % [ 0.14%-0.18 % ] ) ( P < .001 ) , as was aspiration ( 0.14 % [ 0.11%-0.18 % ] vs 0.10 % [ 0.08%-0.12 % ] , respectively ; P = .02 ) . Frequencies of perforation and splenic injury were statistically similar . Other predictors of complications included age greater than 70 years , increasing comorbidity , and performance of the procedure in a hospital setting . In multivariate analysis , use of anesthesia services was associated with an increased complication risk ( odds ratio , 1.46 [ 95 % CI , 
    Output:
    
Compelling and consistent evidence from r and omised controlled trials and observational studies suggests that screening sigmoidoscopy and screening colonoscopy prevent most deaths from distal colorectal cancer .
Observational studies suggest that colonoscopy compared with flexible sigmoidoscopy decreases mortality from cancer of the proximal colon .