***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 Radiotherapy for early breast cancer can decrease breast cancer mortality but increase other mortality , mainly from heart disease and lung cancer . The mean cardiac dose from irradiation of a left-sided breast cancer can be two or three times that for a right-sided breast cancer . The mean ipsilateral ( ie , on the same side as the breast cancer ) lung dose can also be two or three times the mean contralateral lung dose . Particularly during the 1970s , when typical heart and lung exposures were greater than now , the laterality of an irradiated breast cancer could measurably affect cardiac mortality and mortality from cancer of the right or the left lung decades later . This study aim ed to assess the hazards in the general US population from routine cancer-registry and death-certificate data . METHODS We analysed data for 308 861 US women with early breast cancer of known laterality ( left-sided or right-sided ) who were registered in the US Surveillance Epidemiology and End Results ( SEER ) cancer registries during 1973 - 2001 and followed prospect ively for cause-specific mortality until Jan 1 , 2002 . FINDINGS 115 165 ( 37 % ) received radiotherapy . Among those who did not , tumour laterality was of little relevance to subsequent mortality . For women diagnosed during 1973 - 82 and irradiated , the cardiac mortality ratio ( left versus right tumour laterality ) was 1.20 ( 95 % CI 1.04 - 1.38 ) less than 10 years afterwards , 1.42 ( 1.11 - 1.82 ) 10 - 14 years afterwards , and 1.58 ( 1.29 - 1.95 ) after 15 years or more ( trend : 2p=0.03 ) . For women diagnosed during 1983 - 92 and irradiated , the cardiac mortality ratio was 1.04 ( 0.91 - 1.18 ) less than 10 years afterwards and 1.27 ( 0.99 - 1.63 ) 10 or more years afterwards . For women diagnosed during 1993 - 2001 and irradiated the cardiac mortality ratio was 0.96 ( 0.82 - 1.12 ) , with none yet followed for 10 years . Among women irradiated for breast cancer who subsequently developed an ipsilateral or contralateral lung cancer , the lung cancer mortality ratio ( ipsilateral versus contralateral ) for women diagnosed during 1973 - 82 and irradiated was 1.17 ( 0.62 - 2.19 ) , 2.00 ( 1.00 - 4.00 ) , and 2.71 ( 1.65 - 4.48 ) , respectively , less than 10 years , 10 - 14 years , and 15 or more years afterwards ( trend : 2p=0.04 ) . For women irradiated after 1982 there is , as yet , little information on lung cancer risks more than 10 years afterwards . INTERPRETATION US breast cancer radiotherapy regimens of the 1970s and early 1980s appreciably increased mortality from heart disease and lung cancer 10 - 20 years afterwards with , as yet , little direct evidence on the hazards after more than 20 years . Since the early 1980s , improvements in radiotherapy planning should have reduced such risks , but the long-term hazards in the general population s of various countries still need to be monitored directly OBJECTIVES : To estimate women 's expectations of the accuracy of screening mammography and to explore attitudes towards compensation for missed cancers . DESIGN : Cross sectional survey ( by telephone ) . SETTING : Australia ; population -based survey conducted in April 1996 . PARTICIPANTS : R and om sample of women aged 30 - 69 years . A total of 2935 women completed the Breast Health Survey ( adjusted response rate 65 % ) . A r and om sample of 115 completed this sub-survey on perceived sensitivity of mammographic screening and compensation for missed cancers . RESULTS : About one third of women ( 32.2 % , 95 % CI 23.7 , 40.7 ) had an unrealistically high expectation of the sensitivity of screening mammography  , reporting it to be 95 % or higher . Approximately 40 % of the women ( 43.5 % , 95 % CI 34.4 , 52.6 ) thought that screening mammography should pick up all cancers ( should have a sensitivity of 100 % ) . Just under half the women ( 45.2 % , 95 % CI 36.1 , 54.3 ) said financial compensation should be awarded for a cancer missed by screening mammography  even if the cancer was missed as a consequence of the small failure rate of the test . Younger women living in metropolitan areas and women who had realistic expectations of the accuracy of the tests were more likely to favour financial compensation . CONCLUSION : Unrealistically high expectations of the sensitivity of screening mammography  were common in this group of women . Many women favoured financial compensation for missed cancers even if the cancer was missed solely because of the failure rate of the test . Public education is required to inform women of the limited sensitivity of breast cancer tests but this may not reduce cl aims for financial compensation when cancers are missed OBJECTIVE To establish the extent of women 's knowledge of mammographic screening , particularly in relation to the national screening program , BreastScreen Australia , and to estimate the proportion of women who are participating in screening both within and outside BreastScreen Australia . DESIGN AND SETTING Vali date d prospect i ve telephone survey of women aged 30 - 69 years selected at r and om from across Australia . PARTICIPANTS 2935 women with no previous breast cancer diagnosis . RESULTS The adjusted response rate was 64 % . Almost 90 % of women had heard of the national program ; only 1 % correctly stated that screening is for asymptomatic women . 60 % correctly identified the current recommended age of starting screening is about 50 years of age ; 26 % thought screening should begin at about 40 years of age . Approximately 60 % correctly reported that the recommended screening interval is every two years ; 27 % thought screening should be done annually . 55 % reported ever having had a mammogram , and 37 % reported having had at least one screening mammogram . Among women in the target age group ( 50 - 69 years ) about 70 % reported ever having had a screening mammogram , and about 50 % reported having had a screening mammogram within the national program in the last two years . Among women aged 40 - 49 years , 29 % reported ever having had a screening mammogram , and 22 % reported having been screened in the last two years . CONCLUSIONS Awareness of the national screening program is high , but some women do not know the purpose of screening , the target age group and the recommended screening interval . Compliance with screening is good among women in the target age group ; many women in their 40s are also participating in screening For r and omised population trials the unit of r and omisation is normally the individual person . In some situations , however , investigators take other groups as basic unit and one such design is cluster r and omisation . Considerable attention has been given to this design recently in statistical and epidemiological literature . The Edinburgh r and omised trial of breast cancer screening  is an example which takes general practice s as clusters of patients . The experience of this trial is reported here . Mortality from all causes , cardiovascular disease and lung cancer over the first 5 year period of follow up are examined . We found that spurious mortality differences were present in the analyses , which do not allow for socio-economic status . From examination of methods of adjusting for this , we conclude that allowance can be made at the analysis stage , and it is intended that this approach will be adopted when breast cancer mortality is analysed in the Edinburgh trial . Nevertheless , we recommend that for future studies with outcome related to socio-economic status , r and omisations which use this design be stratified by socio-economic criteria where this is feasible A large-scale trial has been started in the United Kingdom with the aim of evaluating the effectiveness of different methods for the early detection of breast cancer . Two population s , each of 25,000 women aged 45 - 64 are invited for annual screening by mammography and /or clinical examination . Two further population s , one of 25,000 and one of 40,000 women in the same age range , are invited for education sessions in breast self-examination , and 4 control population s , totalling 120,000 women , are offered no additional services beyond conventional diagnostic facilities . All breast histology , both benign and malignant , in all women in the study is recorded , as are the findings , management and follow-up of all breast cancers . Changes in the population s , and deaths from all causes , are also recorded . This is essentially a non-r and omized trial , though in one of the screening centres , where an education programme about breast cancer is provided for the whole population , only women registered with certain r and omly selected general practice s are invited to be screened . The principal means of evaluation will be the comparison of the mortality rates from breast cancer in each of the study population s. Costs , in terms of use of health re sources , unnecessary surgery and radiation hazard , will be assessed . Additional aspects of the trial include studies of women 's attitudes to early detection , and of the aetiology of breast cancer A population -based , r and omized , controlled breast cancer screening trial with single-view mammography as the only means of primary detection has been under way in Kopparberg county , Sweden , since October 1977 . The 7-year results of the study show ( 1 ) a significant change in the stage distribution of breast cancers in the cohort invited to undergo screening ( ASP ) as compared to the control group . ( 2 ) This change is seen as an initial decrease in the proportion of advanced ( stage II and more advanced ) cancers in the ASP as compared to the control population , followed in the second and third round of screening by a significant decrease in the absolute number of these advanced cancers in the ASP relative to the control group . ( 3 ) A thorough follow-up of both population s will answer whether these preliminary findings will result in decreased breast cancer mortality in the population invited to screening Although there is evidence for a reduction in breast carcinoma mortality with mammographic screening , some doubts have been expressed , and there is still uncertainty regarding the age specific effects It is the responsibility of the scientist to balance passion with dispassion . John C. Polanyi The Responsibility of the Scientist Department of Physiology Lecture Series : Frontiers in Physiology and Pharmacology , University of Toronto , 22 M Because no previous study evaluating the benefit of screening for breast cancer had specifically addressed efficacy in women aged 40 to 49 years , the results of the Canadian National Breast Screening Study ( NBSS ) were impatiently awaited . When they were finally published in November 1992 [ 1 , 2 ] , the results showed no reduction in breast cancer mortality after 7 years in screened women aged 40 to 49 years . Further , mammography did not achieve an incremental mortality benefit over and above clinical examination in women 50 to 59 years old , although it did achieve higher rates of cancer detection . What one wants to believe is easy to believe . Results from the NBSS , however , were difficult for many to believe . Given the passionately held belief that early detection of breast cancer achieved by mammography screening benefits women aged 40 to 49 years , it was not surprising that the NBSS became the focus of much attention . Some of the criticisms that have been generated are addressed in this article in the hope that a better underst and ing of the issues involved will be reached . Methods Planned in the late 1970s , the NBSS began screening women in January 1980 . Its design [ 3 ] addressed the unanswered questions prevailing at the time . The New York Health Insurance Plan breast screening trial had shown that combined annual screening with mammography and physical examination reduced breast cancer mortality in women 50 years of age and over when compared with no screening [ 4 ] . Although the separate contributions of mammography and physical examination of the breasts to mortality reduction were not known , it was believed that clinical examination of the breasts made a major contribution . Also not known in 1980 was whether combined annual screening  reduced breast cancer mortality in women aged 40 to 49 years when compared with no screening intervention . To determine the benefit of combined screening in women aged 40 to 49 years , the NBSS recruited 50 430 women individually r and omly assigned so that 25 214 received annual mammography and physical examination and 25 216 received a single physical examination  , thereafter returning to usual community care with annual follow-up by mailed question naire . To determine the separate contribution of mammography to breast cancer mortality reduction , 39 405 women ages 50 to 59 years were recruited , of whom 19 711 were r and omly assigned to receive annual mammography and physical examination of the breasts and 19 694 to receive an  annual physical examination alone . Entry criteria included meeting the age criteria , not being pregnant , not having been diagnosed with breast cancer , not having had a mammogram in the 12 months before entry , and signing informed consent forms . Women were instructed in breast self-examination at entry and those eligible for re-screening received repeated instruction and evaluation . All su bmi tted annual question naires that tracked breast procedures generated outside the NBSS . Screening Sites Each of the 15 centers across Canada had an adequate population base from which to draw participants and had recognized expertise in breast cancer . Six centers were in provincial cancer institutions ( all in the forefront of cancer research and treatment ) and eight in university teaching hospitals . Recruitment extended over 6 years , from 1980 
    Output:
    
We found that breast cancer mortality was an unreliable outcome that was biased in favour of screening , mainly because of differential misclassification of cause of death .
Screening is likely to reduce breast cancer mortality .
It is thus not clear whether screening does more good than harm .