***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 
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    Input: Summary In March 1981 , 40,318 women in Stockholm , aged 40–64 , entered a r and omized trial of breast cancer screening by single-view mammography alone versus no intervention in a control group of 20,000 women . The attendance rate during the first screening round was 81 per cent and the cancer detection rate was 4.0 per 1000 women . The detection the rate fell to 3.1 per 1000 in the second round , which was completed in October 1985 . During 1986 the controlled design of the study was broken and the contro women were invited once to screening which was completed the same year . A total of 428 cases of breast cancer were thus diagnosed in the study group and 439 in the adjusted control group . After a mean follow-up of 7.4 years the number of breast cancer deaths in the study and control groups was 39 and 30 respectively . The relative risk of breast cancer death ( screening versus control ) was 0.71 ( 95 per cent confidence interval : 0.4–1.2 ) . Among women older than 50 years at entry the relative risk was 0.57 ( 95 per cent confidence interval : 0.3–1.1 ) . Cancer deaths among women under 50 were few and perhaps because of this no mortality reduction was seen in this age group . The estimate of mortality reduction lies between the results from two earlier Swedish r and omized controlled trials 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 A cross-sectional , r and omized screening with mammary radiography of 15 748 women aged 45 to 69 and living in Malmö for the detection of breast carcinoma is described . The detection rate of breast carcinoma was 7.5 per 1 000 , 16 per cent of the carcinoma being non-invasive and 43 invasive with a diameter of at most 10 mm . The overall rate of axillary metastases was 18 per cent . The sensitivity of the  radiography  was 91.5 per cent , the specificity 99.2 per cent and the predictive value 47 per cent . It is concluded that mammary radiography is an effective screening method for detecting early carcinoma BACKGROUND The Swedish Two-County Trial has been criticised on the grounds of the cluster r and omisation and alleged bias in classification of cause of death . PATIENTS AND METHODS In the Two-County Trial , 77 080 women were r and omised to regular invitation to screening ( active study population , ASP ) and 55 985 to no invitation ( passive study population , PSP ) , in 45 geographical clusters . After approximately 7 years , the PSP was invited to screening and the trial closed . We analysed data using hierarchical statistical models to take account of cluster r and omisation , and performed a conservative analysis assuming a systematic difference between ASP and PSP in baseline breast cancer mortality in one of the counties . We also analysed deaths from causes other than breast cancer and from all causes among breast cancer cases diagnosed in the ASP and PSP . RESULTS Taking account of the cluster r and omisation there was a significant 30 % reduction in breast cancer mortality in the ASP . Conservatively , assuming a systematic difference between ASP and PSP clusters in baseline breast cancer mortality , there was a significant 27 % reduction in mortality in the ASP . Ignoring classification of cause of death , there was a significant 13 % reduction in all-cause mortality in breast cancer cases in the ASP . CONCLUSIONS Breast cancer mortality is a valid end point and mammographic screening does indeed reduce mortality from breast cancer . The criticisms of the Swedish Two-County Trial are unfounded Edinburgh was selected as one of the centres in the UK Seven-year Trial of  Breast Screening of women aged 45 - 65 which began in 1979 . Subsequently , our study was extended to a r and omised trial with its own control population within the city . Half the practice s were r and omly allocated for screening , giving a cluster sampling of women . The total number in the trial is 65,000 . Women with previously diagnosed breast cancer are excluded . Women allocated for screening are invited to the clinic and screened according to the procedures specified in the U.K. protocol , having clinical examination every year and mammography on alternate years . The two modalities of screening are assessed independently and the role of nurses is being evaluated . Breast cancer incidence is monitored by pathology register and the local cancer registry office and deaths from the General Register office . Long-term follow-up will be obtained through flagging at NHS Central Register . To determine the value of screening , st and ard statistical methods will be used to compare breast cancer mortality rates in the whole of the screening population with that of the controls . This trial has a power of 83 % of detecting a reduction in mortality of 35 % after 7 years of follow-up and a power of 95 % of detecting a similar reduction at 10 years ( alpha = 0.05 , one-sided test ) The results of the Swedish two-county trial of mammographic screening for breast cancer are presented , up date d to December 31 , 1990 , which is an average of 10.8 years follow-up per person . The main result of the trial in terms of breast cancer mortality remained the same : compared with the control group , the group invited to screening had a relative breast cancer mortality of 0.70 ( P = 0.0002 ) with 95 % confidence interval ( 0.58 , 0.85 ) . Analysis of survival showed that relative to the control group , the cancers detected at prevalence screen , incidence screens , and in the interval between screens had a good prognosis , whereas cancers detected in those who had refused screening had a very poor prognosis . When adjusted for tumor size , lymph node status , and tumor grade ( differentiation ) , the better survival associated with incidence screen and interval detection was largely accounted for , indicating that the benefit of incidence screening is largely achieved through the effect of screening on the three prognostic variables , notably size of the tumor . Results indicate that to achieve a substantial mortality reduction , 50 % of screen-detected invasive cancers should be less than 15 mm in diameter , at least 30 % of screen-detected grade 3 tumors should be less than 15 mm , and at least 70 % of screen-detected tumors should not have lymph node metastases . The percentage of grade 3 tumors of a given size should be the same in screen-detected cancers as in clinical ly detected , and breast cancer prevalence at first screen should be at least three times the expected incidence rate in the absence of screening . This should be achieved without the recall rate for further examination exceeding 9 % , and procedures including further imaging techniques and fine needle aspiration or core biopsy should be used before resorting to surgical biopsy . These aims can be achieved in specialist screening centers if particular attention is paid to re sources for screening and diagnostic evaluation , specialist training of clinical and technologic screening staff , and ongoing monitoring of mammographic quality , recall rates , and the attributes of the tumors detected BACKGROUND : It has recently been suggested that all-cause mortality is a more appropriate end point than disease specific mortality in cancer screening trials , and that disease specific mortality is biased in favour of screening . This suggestion is based partly on supposed inconsistencies between all-cause mortality results and disease specific results in cancer screening trials , and alleged increases in deaths from causes other than breast cancer among breast cancer cases diagnosed among women invited to screening . METHODS : We used data from the Swedish Two-County Trial of mammographic screening for breast cancer , in which 77 080 women were r and omised to an invitation to screening and 55 985 to no invitation .  We estimated relative risks ( RRs ) ( invited v control ) of death from breast cancer , death from other causes within the breast cancer cases , and death from all causes within the breast cancer cases . RRs were adjusted for age and took account of the longer follow up of breast cancer cases in the invited group due to lead time . RESULTS : There was a significant 31 % reduction in breast cancer mortality in the invited group ( RR 0.69 , 95 % confidence interval ( CI ) 0.58–0.80 ; p<0.001 ) . There was no significant increase in deaths from other causes among breast cancer cases in the invited group ( RR 1.12 , 95 % CI 0.96–1.31 ; p=0.14 ) . A significant 19 % reduction in deaths from all causes was observed among breast cancer cases in the group invited to screening ( RR 0.81 , 95 % CI 0.72–0.90 ; p<0.001 ) . A more conservative estimation gave a significant 13 % reduction ( RR 0.87 , 95 % CI 0.78–0.97 ; p=0.01 ) . These findings are consistent with the magnitude of the reduction in breast cancer mortality . CONCLUSIONS : Invitation to screening was associated with a reduction in deaths from all causes among breast cancer cases , consistent with high participation rates in screening . There is no significant evidence of bias in cause of death classification in the Two-County Trial , and as breast cancer mortality is the targeted clinical outcome in breast cancer screening , it is the appropriate end point in a breast cancer screening trial . All-cause mortality is a poor and inefficient surrogate for breast cancer mortality First results in a long-term investigation to determine whether periodic breast cancer screening with mammography and clinical examination leads to lowered  breast cancer mortality provide grounds for cautious optimism . The study compares the experience in a r and om sample of 31,000 women , aged 40 to 64 years , offered screening examinations with the experience in a similarly constituted " control " group . There were 52 deaths due to breast cancer in the control group , as compared with 31 breast cancer deaths in the study group , in the period available for follow-up . The 3 1/2-year case fatality rates among women with histologically confirmed breast cancers reinforce the impression that screening leads to lowered mortality . More time , possibly ten years of follow-up , is needed to establish whether the effect of the screening program is short-term or long-term The Swedish two county trial of breast cancer screening  is now in its tenth year . This paper presents detailed results on mortality from breast cancer and from all other causes , and on the population denominators at risk for each of the first 8 years of follow 
    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 likely reduces breast cancer mortality .
It is thus not clear whether screening does more good than harm .