***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: Objectives : To investigate the effectiveness of screening for liver cancer in reducing mortality from the disease in a high-risk population in China . Setting : A r and omised controlled trial was carried out among men aged 30 - 69 who were chronic carriers of hepatitis-B virus ( HBsAg positive ) during the period 1989 - 1995 in Qidong county , Jiangsu Province , China . Methods : 5581 HBsAg carriers were identified by population screening and r and omly assigned to a screening group ( group A , 3712 men ) , and controls ( group B , 1869 men ) . Screening was planned to be six monthly alpha-fetoprotein ( AFP ) assays , with follow-up of subjects having an abnormal ( ≥20 μg/l ) test . All subjects were followed up for liver cancer and /or death until 31 December 1995 . Results : The overall sensitivity and specificity of the programme was 55.3 % and 86.5 % , respectively ; in subjects who complied with all scheduled screening tests , the values were 80.0 % and 80.9 % . Three hundred and seventy-four primary liver cancer ( PLC ) cases were diagnosed . The percentage of cases in stage I was significantly higher in group A ( 29.6 % ) than in group B ( 6.0 % ) . The one- , three- , and five-year relative survival rates were 23.7 % , 7.0 % , and 4.0 % in group A , and 9.7 % , 4.0 % , and 4.1 % in group B respectively , with no difference in five-year survival between the groups . The mortality rate in the screened group ( 1138 per 100,000 person-years ) was not significantly different from that in the controls ( 1114 per 100,000 ) . A Poisson regression model showed that the probability of death ( rate ratio ) in the screening group was 0.83 ( 95 % CI 0.68 - 1.03 ) relative to the control group . Conclusions : Screening with AFP result ed in earlier diagnosis of liver cancer , but the gain in lead time did not result in any overall reduction in mortality , because therapy for the patients found by screening was ineffective . Further studies using improved methods of screening , diagnosis and treatment are indicated BACKGROUND The European R and omized Study of Screening for Prostate Cancer was initiated in the early 1990s to evaluate the effect of screening with prostate-specific-antigen ( PSA ) testing on death rates from prostate cancer . METHODS We identified 182,000 men between the ages of 50 and 74 years through registries in seven European countries for inclusion in our study . The men were r and omly assigned to a group that was offered PSA screening at an average of once every 4 years or to a control group that did not receive such screening . The predefined core age group for this study included 162,243 men between the ages of 55 and 69 years . The primary outcome was the rate of death from prostate cancer . Mortality follow-up was identical for the two study groups and ended on December 31 , 2006 . RESULTS In the screening group , 82 % of men accepted at least one offer of screening . During a median follow-up of 9 years , the cumulative incidence of prostate cancer was 8.2 % in the screening group and 4.8 % in the control group . The rate ratio for death from prostate cancer in the screening group , as compared with the control group , was 0.80 ( 95 % confidence interval [ CI ] , 0.65 to 0.98 ; adjusted P=0.04 ) . The absolute risk difference was 0.71 death per 1000 men . This means that 1410 men would need to be screened and 48 additional cases of prostate cancer would need to be treated to prevent one death from prostate cancer . The analysis of men who were actually screened during the first round ( excluding subjects with noncompliance ) provided a rate ratio for death from prostate cancer of 0.73 ( 95 % CI , 0.56 to 0.90 ) . CONCLUSIONS PSA-based screening reduced the rate of death from prostate cancer by 20 % but was associated with a high risk of overdiagnosis . ( Current Controlled Trials number , IS RCT N49127736 . BACKGROUND The effect of screening with prostate-specific-antigen ( PSA ) testing and digital rectal examination on the rate of death from prostate cancer is unknown . This is the first report from the Prostate , Lung , Colorectal , and Ovarian ( PLCO ) Cancer Screening Trial on prostate-cancer mortality . METHODS From 1993 through 2001 , we r and omly assigned 76,693 men at 10 U.S. study centers to receive either annual screening ( 38,343 subjects ) or usual care as the control ( 38,350 subjects ) . Men in the screening group were offered annual PSA testing for 6 years and digital rectal examination for 4 years . The subjects and health care providers received the results and decided on the type of follow-up evaluation . Usual care sometimes included screening , as some organizations have recommended . The numbers of all cancers and deaths and causes of death were ascertained . RESULTS In the screening group , rates of compliance were 85 % for PSA testing and 86 % for digital rectal examination . Rates of screening in the control group increased from 40 % in the first year to 52 % in the sixth year for PSA testing and ranged from 41 to 46 % for digital rectal examination . After 7 years of follow-up , the incidence of prostate cancer per 10,000 person-years was 116 ( 2820 cancers ) in the screening group and 95 ( 2322 cancers ) in the control group ( rate ratio , 1.22 ; 95 % confidence interval [ CI ] , 1.16 to 1.29 ) . The incidence of death per 10,000 person-years was 2.0 ( 50 deaths ) in the screening group and 1.7 ( 44 deaths ) in the control group ( rate ratio , 1.13 ; 95 % CI , 0.75 to 1.70 ) . The data at 10 years were 67 % complete and consistent with these overall findings . CONCLUSIONS After 7 to 10 years of follow-up , the rate of death from prostate cancer was very low and did not differ significantly between the two study groups . ( Clinical Trials.gov number , NCT00002540 . PURPOSE This clinical trial is aim ed at evaluating the impact of prostate cancer screening on cancer-specific mortality . SUBJECTS AND METHODS Forty-six thous and four hundred and eighty-six ( 46,486 ) men aged 45 - 80 years registered in the electoral roll of the Quebec city area were r and omized in 1988 between screening and no screening . Screening included measurement of serum prostatic specific antigen ( PSA ) using 3.0 ng/ml as upper limit of normal and digital rectal examination ( DRE ) at first visit . At follow-up visits , serum PSA only was used . RESULTS Seventy-four ( 74 ) deaths from prostate cancer occurred in the 14,231 unscreened controls while 10 deaths were observed in the screened group of 7,348 men during the first 11 years following r and omization . Median follow-up of screened men was 7.93 years . A Cox proportional hazards model of the age at death from prostate cancer shows a 62 % reduction ( P < 0.002 , Fisher 's exact test ) of cause-specific mortality in the screened men ( P = 0.005 ) . These results are in agreement with the continuous decrease of prostate cancer mortality observed in North America Purpose Screening for hepatocellular carcinoma ( HCC ) has been conducted for over 20 years , but there is no conclusive evidence that screening may reduce HCC mortality . The aim of this study was to assess the effect of screening on HCC mortality in people at increased risk . Methods This study included 18,816 people , aged 35–59 years with hepatitis B virus infection or a history of chronic hepatitis in urban Shanghai , China . Participants were r and omly allocated to a screening ( 9,373 ) or control ( 9,443 ) group . Controls received no screening and continued to use health-care facilities . Screening group participants were invited to have an AFP test and ultrasonography examination every 6 months . Screening was stopped in December 1997 ; by that time screening group participants had been offered five to ten times . All participants were followed up until December 1998 . The primary outcome measure was HCC mortality . Results The screened group completed 58.2 percent of the screening offered . When the screening group was compared to the control group , the number of HCC was 86 versus 67 ; sub clinical HCC being 52 ( 60.5 % ) versus 0 ; small HCC 39 ( 45.3 % ) versus 0 ; resection achieved 40 ( 46.5 % ) versus 5 ( 7.5 % ) ; 1- , 3,- , and 5-year survival rate 65.9 % , 52.6 % , 46.4 % versus 31.2 % , 7.2 % , 0 , respectively . Thirty-two people died from HCC in the screened group versus 54 in the control group , and the HCC mortality rate was significantly lower in the screened group than in controls , being 83.2/100,000 and 131.5/100,000 , respectively , with a mortality rate ratio of 0.63 ( 95%CI 0.41–0.98 ) . Conclusions Our finding indicated that biannual screening reduced HCC mortality by 37 % Stored sample s from women in the Stockholm screening study were reassayed for CA125II ( Centocor , Malvern , PA ) and OVX1 . The postmenopausal women older than age 50 without ovarian cancer were r and omly split into a training set to develop a screening test based on longitudinal marker levels and a second set to vali date the test . The CA125II data from each woman is summarized by the slope and intercept from a linear regression of log(CAl25II ) on time since first sample . The slope versus the intercept for the training set and the ovarian cancer cases formed a bivariate scatter plot . A curve was drawn on the scatter plot that separated most of the women with ovarian cancer from all other women ; it delineated a screening test . The specificity of this test was examined on the validation set with a specificity of 99.8 % . Bayes ' theorem was used to calculate the risk of ovarian cancer ( ROC ) based on the intercept , slope , and assay variability . It is important to account for assay variability because it can produce large slopes over short periods of time . The maximum risk , which identified 83 % ( 5 of 6 ) of the ovarian cancers detected within a year of last assay , was applied as a test to the training set and confirmed a high specificity of 99.7 % . With this specificity and sensitivity , the ROC algorithm using the CA125II assay has an estimated positive predictive value of 16 % , substantially greater than the positive predictive value based on a single assay . Further study is planned to confirm the sensitivity of this approach . Cancer 1995 ; 76:2004‐10 New stool tests may be promising tools for future colorectal cancer ( CRC ) screening . The aim of this review was to summarize current evidence of performance characteristics and practicalness in a population ‐based screening setting of recently developed stool tests . The MEDLINE data base was search ed for relevant articles published until July 2004 . Studies were included if they comprised more than 10 cases and more than 10 controls . Details on study population , performance characteristics and stool collection procedure were taken into account . Overall , 29 studies , mostly retrospective , were included , investigating 17 different stool markers or marker combinations . Underlying study population s were very heterogeneous and mostly very small . Half of the studies reported sensitivity for adenomas in addition to sensitivity for CRC , and fewer than half reported sensitivity by tumor stage or location . Performance characteristics of  stool tests  varied to a large extent . For most DNA‐based markers , specificity was about 95 % or higher , but sensitivity was mostly low even for invasive CRC . More studies with larger sample sizes were done for protein‐based markers , which typically had lower specificity . In most studies , stool sample s were frozen within a rather short time period after defecation . While promising performance characteristics have been reported for some tests , more pervasive evidence from larger , prospect ively design ed studies , which also consider aspects of practicalness , e.g. , the possibility of mailing the sample s , is needed . © 2005 Wiley‐Liss , PURPOSE To evaluate prevalence screening in the first prospect i ve trial of a new ovarian cancer screening ( OCS ) strategy ( risk of ovarian cancer or ROC algorithm ) on the basis of age and CA125 profile . PATIENTS AND METHODS Postmenopausal women , > or = 50 years were r and omly assigned to a control group or screen group . Screening involved serum CA125 , interpreted using the ROC algorithm .  Participants with normal results returned to annual screening ; those with intermediate results had repeat CA125 testing ; and those with elevated values underwent transvaginal ultrasound ( TVS ) . Women with abnormal or persistently equivocal TVS were referred for a gynecologic opinion . RESULTS Thirteen thous and five hundred eighty-two women were recruited . Of 6,682 women r and omly assigned to screening , 6, 
    Output:
    
Of these markers , only the use of FOBT in screening for CRC has been shown to reduce mortality from cancer .
This lack of sensitivity and specificity when combined with the low prevalence of cancers in the general population means that most biomarkers , if used alone , have a low positive predictive value in screening asymptomatic population s. Indeed , it is the low prevalence of cancer in the general population that prohibits most biomarkers from being used alone , in screening for cancer ( 4,5 ) .