***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 Low-dose CT screening is recommended for individuals at high risk of developing lung cancer . However , CT screening does not detect all lung cancers : some might be missed at screening , and others can develop in the interval between screens . The NELSON trial is a r and omised trial to assess the effect of screening with increasing screening intervals on lung cancer mortality . In this prespecified analysis , we aim ed to assess screening test performance , and the epidemiological , radiological , and clinical characteristics of interval cancers in NELSON trial participants assigned to the screening group . METHODS Eligible participants in the NELSON trial were those aged 50 - 75 years , who had smoked 15 or more cigarettes per day for more than 25 years or ten or more cigarettes for more than 30 years , and were still smoking or had quit less than 10 years ago . We included all participants assigned to the screening group who had attended at least one round of screening . Screening test results were based on volumetry using a two-step approach . Initially , screening test results were classified as negative , indeterminate , or positive based on nodule presence and volume . Subsequently , participants with an initial indeterminate result underwent follow-up screening to classify their final screening test result as negative or positive , based on nodule volume doubling time . We obtained information about all lung cancer diagnoses made during the first three rounds of screening , plus an additional 2 years of follow-up from the national cancer registry . We determined epidemiological , radiological , participant , and tumour characteristics by reassessing medical files , screening CTs , and clinical CTs . The NELSON trial is registered at www.trialregister.nl , number IS RCT N63545820 . FINDINGS 15,822 participants were enrolled in the NELSON trial , of whom 7915 were assigned to low-dose CT screening  with increasing interval between screens , and 7907 to no screening .  We included 7155 participants in our study , with median follow-up of 8·16 years ( IQR 7·56 - 8·56 ) . 187 ( 3 % ) of 7155 screened participants were diagnosed with 196 screen-detected lung cancers , and another 34 ( < 1 % ; 19 [ 56 % ] in the first year after screening , and 15 [ 44 % ] in the second year after screening ) were diagnosed with 35 interval cancers . For the three screening rounds combined , with a 2-year follow-up , sensitivity was 84·6 % ( 95 % CI 79·6 - 89·2 ) , specificity was 98·6 % ( 95 % CI 98·5 - 98·8 ) , positive predictive value was 40·4 % ( 95 % CI 35·9 - 44·7 ) , and negative predictive value was 99·8 % ( 95 % CI 99·8 - 99·9 ) . Retrospective assessment of the last screening CT and clinical CT in 34 patients with interval cancer showed that interval cancers were not visible in 12 ( 35 % ) cases . In the remaining cases , cancers were visible when retrospectively assessed , but were not diagnosed because of radiological detection and interpretation errors ( 17 [ 50 % ] ) , misclassification by the protocol ( two [ 6 % ] ) , participant non-compliance ( two [ 6 % ] ) , and non-adherence to protocol ( one [ 3 % ] ) . Compared with screen-detected cancers , interval cancers were diagnosed at more advanced stages ( 29 [ 83 % ] of 35 interval cancers vs 44 [ 22 % ] of 196 screen-detected cancers diagnosed in stage III or IV ; p<0·0001 ) , were more often small-cell carcinomas ( seven [ 20 % ] vs eight [ 4 % ] ; p=0·003 ) and less often adenocarcinomas ( nine [ 26 % ] vs 102 [ 52 % ] ; p=0·005 ) . INTERPRETATION Lung cancer screening in the NELSON trial yielded high specificity and sensitivity , with only a small number of interval cancers . The results of this study could be used to improve screening algorithms , and reduce the number of missed cancers . FUNDING Zorgonderzoek Nederl and Medische Wetenschappen and Koningin Wilhelmina Fonds BACKGROUND The aggressive and heterogeneous nature of lung cancer has thwarted efforts to reduce mortality from this cancer through the use of screening . The advent of low-dose helical computed tomography ( CT ) altered the l and scape of lung-cancer screening , with studies indicating that low-dose CT detects many tumors at early stages . The National Lung Screening Trial ( NLST ) was conducted to determine whether screening with low-dose CT could reduce mortality from lung cancer . METHODS From August 2002 through April 2004 , we enrolled 53,454 persons at high risk for lung cancer at 33 U.S. medical centers . Participants were r and omly assigned to undergo three annual screenings with either low-dose CT ( 26,722 participants ) or single-view posteroanterior chest radiography ( 26,732 ) . Data were collected on cases of lung cancer and deaths from lung cancer that occurred through December 31 , 2009 . RESULTS The rate of adherence to screening was more than 90 % . The rate of positive screening tests was 24.2 % with low-dose CT and 6.9 % with radiography over all three rounds . A total of 96.4 % of the positive screening results in the low-dose CT group and 94.5 % in the radiography group were false positive results . The incidence of lung cancer was 645 cases per 100,000 person-years ( 1060 cancers ) in the low-dose CT group , as compared with 572 cases per 100,000 person-years ( 941 cancers ) in the radiography group ( rate ratio , 1.13 ; 95 % confidence interval [ CI ] , 1.03 to 1.23 ) . There were 247 deaths from lung cancer per 100,000 person-years in the low-dose CT group and 309 deaths per 100,000 person-years in the radiography group , representing a relative reduction in mortality from lung cancer with low-dose CT screening of 20.0 % ( 95 % CI , 6.8 to 26.7 ; P=0.004 ) . The rate of death from any cause was reduced in the low-dose CT group , as compared with the radiography group , by 6.7 % ( 95 % CI , 1.2 to 13.6 ; P=0.02 ) . CONCLUSIONS Screening with the use of low-dose CT reduces mortality from lung cancer . ( Funded by the National Cancer Institute ; National Lung Screening Trial Clinical Trials.gov number , NCT00047385 . ) BACKGROUND The Mayo Lung Project ( MLP ) was a r and omized , controlled clinical trial of lung cancer screening that was conducted in 9211 male smokers between 1971 and 1983 . The intervention arm was offered chest x-ray and sputum cytology every 4 months for 6 years ; the usual-care arm was advised at trial entry to receive the same tests annually . No lung cancer mortality benefit was evident at the end of the study . We have extended follow-up through 1996 . METHODS A National Death Index-PLUS search was used to assign vital status and date and cause of death for 6523 participants with unknown information . The median survival for lung cancer patients diagnosed before July 1 , 1983 , was calculated by use of Kaplan-Meier estimates . Survival curves were compared with the log-rank test . RESULTS The median follow-up time was 20.5 years . Lung cancer mortality was 4.4 ( 95 % confidence interval [ CI ] = 3.9 - 4.9 ) deaths per 1000 person-years in the intervention arm and 3.9 ( 95 % CI = 3.5 - 4.4 ) in the usual-care arm ( two-sided P : for difference = .09 ) . For participants diagnosed with lung cancer before July 1 , 1983 , survival was better in the intervention arm ( two-sided P : = .0039 ) . The median survival for patients with resected early-stage disease was 16.0 years in the intervention arm versus 5.0 years in the usual-care arm . CONCLUSIONS Extended follow-up of MLP participants did not reveal a lung cancer mortality reduction for the intervention arm . Similar mortality but better survival for individuals in the intervention arm indicates that some lesions with limited clinical relevance may have been identified in the intervention arm RATIONALE Screening for lung cancer with modern imaging technology may decrease lung cancer mortality , but encouraging results have only been obtained in uncontrolled studies . OBJECTIVES To explore the effect of screening with low-dose spiral computed tomography ( LDCT ) on lung cancer mortality . Secondary endpoints are incidence , stage at diagnosis , and resectability . METHODS Male subjects , aged 60 to 75 years , smokers of 20 or more pack-years , were r and omized to screening with LDCT or control groups .  All participants underwent a baseline , once-only chest X-ray and sputum cytology examination . Screening-arm subjects had LDCT upon accrual to be repeated every year for 4 years , whereas controls had a yearly medical examination only . MEASUREMENTS AND MAIN RESULTS A total of 2,811 subjects were r and omized and 2,472 were enrolled ( LDCT , 1,276 ; control , 1,196 ) . After a median follow-up of 33 months , lung cancer was detected in 60 ( 4.7 % ) patients receiving LDCT and 34 ( 2.8 % ) control subjects ( P = 0.016 ) . Resectability rates were similar in both groups . More patients with stage I disease were detected by LDCT ( 54 vs. 34 % ; P = 0.06 ) and fewer cases were detected in the screening arm due to intercurrent symptoms . However , the number of advanced lung cancer cases was the same as in the control arm . Twenty patients in the LDCT group ( 1.6 % ) and 20 controls ( 1.7 % ) died of lung cancer , whereas 26 and 25 died of other causes , respectively . CONCLUSIONS The mortality benefit from lung cancer screening by LDCT might be far smaller than anticipated Purpose Low-dose multislice-CT ( MSCT ) detects many early-stage lung cancers with good prognosis , but whether it decreases lung cancer mortality and at which costs is yet insufficiently explored . Scope of the present study is to examine within a common European effort whether MSCT screening is capable to reduce the lung cancer mortality by at least 20 % and at which amount of undesired side effects this could be achieved . Methods Overall 4,052 heavy smoking men and women were recruited by a population -based approach and r and omized into a screening arm with five annual MSCT screens and an initial quit-smoking counseling , and a control arm with initial quit-smoking counseling and five annual question naire inquiries . Results In the first screening round , 2,029 participants received a MSCT  providing 1,488 negative and 540 suspicious screens with early recalls ( early recall rate 26.6 % ) leading to 31 biopsies ( biopsy rate 1.5 % ) and 22 confirmed lung cancers ( detection rate 1.1 % ) . Among the lung cancers , 15 were adenocarcinomas , 3 squamous cell carcinomas , one small-cell lung cancer , and 3 others , whereby 18 were in clinical stage I , one in stage II , and 3 in stage III . One interval cancer occurred . Conclusions The indicated performance indicators fit into the range observed in comparable trials . The study continues finalizing the second screening round and for the first participants even the last screening round . The unresolved issue of the precise amount of side effects and the high early recall rate precludes currently the recommendation of MSCT as screening tool for lung cancer In a r and omized prospect i ve study of lung cancer detection in a high-risk population of over 6000 heavy smokers semiannual screening by X-ray and sputum cytology was compared to screening at a 3-year interval . The comparison of Kaplan-Meier estimates of survival curves done without and with correcting for lead-time bias disclosed a rather important impact of lead-time bias on survival comparisons . On the contrary , controlling for possible length bias had no obvious effect on the shape of survival curves . The evaluation of mortality from lung cancer , being used as a basic criterion , indicated no traceable benefit from semiannual screening . The higher incidence of lung cancer in the frequently screened group was paralleled by a higher mortality . It is concluded that currently available screening techniques will not solve the problem of lung cancer mortality in smokers . The results underline the importance of primary prevention for lung cancer The study was launched in the mid‐1970s to explore the capability of screening by chest X‐ray and sputum cytology to be used as an effective component of the lung cancer control program in the Czech Republic , a Central European country with a high and increasing occurrence of lung cancer in men at that time . A complementary objective of this report is to ascertain whether the cumulative numbers of lung cancer deaths would equalize in the two r and omized groups during a prolonged follow‐up period THE R AND OMIZED controlled trial ( RCT ) , more than any other methodology , can have a powerful and immediate impact on patient care . Ideally , the report of such an evaluation needs to convey to the reader relevant information 
    Output:
    
There was a statistically non-significant increase in all-cause mortality .
The results showed that in terms of lung cancer mortality reduction  LDCT was ranked as the best screening strategy , CXR screening as the worst strategy and usual care intermediate .