***TASK*** the task is to summarize 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 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 Objective To compare breast cancer incidence and mortality up to 25 years in women aged 40 - 59 who did or did not undergo mammography screening .  Design Follow-up of r and omised screening trial by centre coordinators , the study ’s central office , and linkage to cancer registries and vital statistics data bases . Setting 15 screening centres in six Canadian provinces,1980 - 85 ( Nova Scotia , Quebec , Ontario , Manitoba , Alberta , and British Columbia ) . Participants 89 835 women , aged 40 - 59 , r and omly assigned to mammography  ( five annual mammography screens ) or control ( no mammography ) . Interventions Women aged 40 - 49 in the mammography arm and all women aged 50 - 59 in both arms received annual physical breast examinations . Women aged 40 - 49 in the control arm received a single examination followed by usual care in the community . Main outcome measure Deaths from breast cancer . Results During the five year screening period , 666 invasive breast cancers were diagnosed in the  mammography arm ( n=44 925 participants ) and 524 in the controls ( n=44 910 ) , and of these , 180 women in the mammography arm and 171 women in the control arm died of breast cancer during the 25 year follow-up period . The overall hazard ratio for death from breast cancer diagnosed during the screening period associated with mammography was 1.05 ( 95 % confidence interval 0.85 to 1.30 ) . The findings for women aged 40 - 49 and 50 - 59 were almost identical . During the entire study period , 3250 women in the mammography arm and 3133 in the control arm had a diagnosis of breast cancer , and 500 and 505 , respectively , died of breast cancer . Thus the cumulative mortality from breast cancer was similar between women in the mammography arm and in the control arm ( hazard ratio 0.99 , 95 % confidence interval 0.88 to 1.12 ) . After 15 years of follow-up a residual excess of 106 cancers was observed in the mammography arm , attributable to over-diagnosis . Conclusion Annual mammography in women aged 40 - 59 does not reduce mortality from breast cancer beyond that of physical examination or usual care when adjuvant therapy for breast cancer is freely available . Overall , 22 % ( 106/484 ) of screen detected invasive breast cancers were over-diagnosed , representing one over-diagnosed breast cancer for every 424 women who received mammography screening in the trial Objective To assess the incidence of early stage  and advanced stage breast cancer  before and after the implementation of  mass screening in women aged 70 - 75 years in the Netherl and s in 1998 . Design Prospect i ve nationwide population based study . Setting National cancer registry , the Netherl and s. Participants Patients aged 70 - 75 years with a diagnosis of invasive or ductal carcinoma in situ breast cancer between 1995 and 2011 ( n=25 414 ) .  Incidence rates were calculated using population data from Statistics Netherl and s. Main outcome measure Incidence rates of early stage ( I , II , or ductal carcinoma in situ ) and advanced stage ( III and IV ) breast cancer before and after implementation of screening . Hypotheses were formulated before data collection . Results The incidence of early stage tumours significantly increased after the extension for implementation of screening ( 248.7 cases per 100 000 women before screening up to 362.9 cases per 100 000 women after implementation of screening , incidence rate ratio 1.46 , 95 % confidence interval 1.40 to 1.52 , P<0.001 ) . However , the incidence of advanced stage breast cancers decreased to a far lesser extent ( 58.6 cases per 100 000 women before screening to 51.8 cases per 100 000 women after implementation of screening , incidence rate ratio 0.88 , 0.81 to 0.97 , P<0.001 ) . Conclusions The extension of the upper age limit to 75 years has only led to a small decrease in incidence of advanced stage breast cancer , while that of early stage tumours has strongly increased 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 Results from several r and omised mammography screening trials haveshown that it is possible to reduce mortalityin breast cancer by mammographic screening at leastfor women above 50 years of age . The purpose of this article is to present data on mortality in breast cancer  in study and control groups of the Stockholm trial after 11years of followup , to analyse which age group benefits most from screening . In March 1981 , 40,318women in Stockholm , aged 40 through 64 years , entered a r and omized trial of breast cancer screeningby single view mammography alone , versus no interventionin a control group of 20 000 women . Two screening rounds were performed and the attendancerate was over 80 % in the two rounds . During 1986 the control group was invited onceto screening .  Totally 428 and 217 cases ofbreast cancer were diagnosed in the study and control groups respectively . After a mean follow-up of11.4 years a nonsignificant mortality reduction of 26%was observed for the whole study group , witha relative risk ( RR ) of death in breastcancer of 0.74 ( CI(confidence interval)=0.5–1.1 ) . Forwomen aged 50–64 years a significant 38 % mortalityreduction was observed with a RR of 0.62(CI=0.38–1.0 ) . For women aged 40–49 yearsno effect on mortality was found , with aRR of death in breast cancer of 1.08(CI=0.54–2.17 ) . The breakpoint for benefit inthis study seemed to be at 50 yearsof age when 5-year age groups were analysed , but this tendency is uncertain because of thelow statistical power in the analysis of theyounger age groups . Long screening intervals , the useof single-view mammography , and the fact that morethan 50 % of the women in age group40–49 years were still below 50 years ofage when the study was closed , were allfacts that could have influenced the results inage group 40–49 years . Larger studies are neededto answer the question whether mammographic screening canbe successful in younger age groups Despite encouraging results from screening trials the efficacy of mammography in reducing mortality remains somewhat controversial . Five studies have been done in Sweden . This overview , based on 282,777 women followed for 5 - 13 years in r and omised trials in Malmö , Kopparberg , Ostergötl and , Stockholm , and Gothenburg , reveals a 24 % ( 95 % confidence interval 13 - 34 % ) significant reduction of breast cancer mortality among those invited to mammography screening  compared with those not invited . To avoid the potential risk of differential misclassification causes of death were assessed by an independent end-point committee after a blinded review of all fatal breast cancer cases . The mortality reduction was similar , irrespective of the end-point used for evaluation ( " breast cancer as underlying cause of death " or " breast cancer present at death " ) . There was a consistent risk reduction associated with screening in all studies , although the point estimate of the relative risk for all ages varied non-significantly between 0.68 and 0.84 . The cumulative breast cancer mortality by time since r and omisation was estimated at 1.3 per 1000 within 6 years in the invited group compared with 1.6 in the control group . The corresponding figures after 9 years are 2.6 and 3.3 and after 12 years 3.9 and 5.1 . The largest reduction of breast cancer mortality ( 29 % ) was observed among women aged 50 - 69 at r and omisation . Among women 40 - 49 there was a non-significant 13 % reduction . In this younger age group cumulative breast cancer mortality was similar in the invited and control group during the first 8 years of follow-up . After 8 years there was a difference in favour of the invited women . There was no evidence of any detrimental effect of screening in terms of breast cancer mortality in any age group . Among women aged 70 - 74 years screening seems to have had only a marginal impact A r and omised controlled trial to investigate the efficacy of mass screening with single-view mammography in reducing mortality from breast cancer  was started in Sweden in 1977 . 162 981 women aged 40 years or more and living in the counties of Kopparberg and Ostergötl and were enrolled in the study and divided at r and om into 2 groups . Each woman in the study group was offered screening every 2 or 3 years depending on age . Women in the control group were not offered screening . This report is confined to the 134 867 women aged 40 - 74 years at date of entry . The results to the end of 1984 show a 31 % reduction in mortality from breast cancer and a 25 % reduction in the rate of stage II or more advanced breast cancers in the group invited to screening . 7 years after the start of the study the excess of stage I cancers in the study group largely outweighs the deficit of advanced cancers This article provides additional follow-up data of two cohorts from the Malmö Mammographic Screening Trial ( MMST ) . The first cohort , MMST I , contained 7,984 women under age 50 at entry into MMST who were born between 1927 and 1932 . Half were assigned to a control group and were not invited for examination until four years after the code was broken in the MMST in 1988 . The second cohort , MMST II , contained 17,786 women born between 1933 and 1945 . Fifty four percent of these women were r and omly invited to screening between 1978 and 1990 . The remaining 46%--the  control group --  was invited to screening between 1991 and 1994 . Nine screening rounds were completed in MMST I , and a mean of five rounds were completed in MMST II ; the screening interval 
    Output:
    
Conclusions The use of unconventional statistical methods in Swedish trials has led to overestimation of risk reduction in breast cancer death attributable to mammography screening .
The constant risk reduction observed in screening groups was probably due to the trial design that optimised awareness and medical management of women allocated to screening groups