***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: R and omised controlled trials have shown that the policy of mammographic screening confers a substantial and significant reduction in breast cancer mortality . This has often been accompanied , however , by an increase in breast cancer incidence , particularly during the early years of a screening programme , which has led to concerns about overdiagnosis , that is to say , the diagnosis of disease that , if left undetected and therefore untreated , would not become symptomatic . We used incidence data from two r and omised controlled trials of mammographic screening , the Swedish Two-county Trial and the Gothenburg Trial , to establish the timing and magnitude of any excess incidence of invasive disease and ductal carcinoma in situ ( DCIS ) in the study groups , to ascertain whether the excess incidence of DCIS reported early in a screening trial is balanced by a later deficit in invasive disease and provide explicit estimates of the rate of ' real ' and non-progressive ' overdiagnosed ' tumours from the study groups of the trials . We used a multistate model for overdiagnosis and used Markov Chain Monte Carlo methods to estimate the parameters . After taking into account the effect of lead time , we estimated that less than 5 % of cases diagnosed at prevalence screen and less than 1 % of cases diagnosed at incidence screens are being overdiagnosed . Overall , we estimate overdiagnosis to be around 1 % of all cases diagnosed in screened population s. These estimates are , however , subject to considerable uncertainty . Our results suggest that overdiagnosis in mammography screening is a minor phenomenon , but further studies with very large numbers are required for more precise estimation Abstract Objective To evaluate the rate of over-diagnosis of breast cancer 15 years after the end of the Malmö mammographic screening trial . Design Follow-up study . Setting Malmö , Sweden . Subjects 42 283 women aged 45 - 69 years at r and omisation . Interventions Screening for breast cancer with mammography or not ( controls ) . Screening was offered at the end of the r and omisation design to both groups aged 45 - 54 at r and omisation but not to groups aged 55 - 69 at r and omisation . Main outcome measures Rate of over-diagnosis of breast cancer ( in situ and invasive ) , calculated as incidence in the invited and control groups , during period of r and omised design ( period 1 ) , during period after r and omised design ended ( period 2 ) , and at end of follow-up . Results In women aged 55 - 69 years at r and omisation the relative rates of over-diagnosis of breast cancer ( 95 % confidence intervals ) were 1.32 ( 1.14 to 1.53 ) for period 1 , 0.92 ( 0.79 to 1.06 ) for period 2 , and 1.10 ( 0.99 to 1.22 ) at the end of follow-up . Conclusion Conclusions on over-diagnosis of breast cancer in the Malmö mammographic screening trial can be drawn mainly for women aged 55 - 69 years at r and omisation whose control groups were never screened . Fifteen years after the trial ended the rate of over-diagnosis of breast cancer was 10 % in this age group Data from r and omised controlled trials of mammographic screening  can be used to determine the extent of any overdiagnosis , as soon as either a time equivalent to the lead-time has elapsed after the final screen , or the control arm has been offered screening . This paper review s those r and omised trials for which breast cancer incidence data are available . In recent trials in which the control group has not been offered screening , an excess incidence of breast cancer remains after many years of follow-up . In those trials in which the control arm has been offered screening , although there is a possible shift from invasive to in situ disease , there is no evidence of overdiagnosis as a result of incident screens Whether a recent large decline in use of postmenopausal hormone therapy after the release of the Women 's Health Initiative findings in July 2002 and /or a decline in screening mammography use is related to a recently reported decline in breast cancer incidence in the United States is controversial . We prospect ively collected data from four screening mammography registries from January 1997 through December 2003 for 603411 screening mammography examinations performed on women aged 50 - 69 years . Of these women , 3238 were diagnosed with breast cancer within 12 months of a screening examination . We calculated quarterly rates of self-reported current postmenopausal hormone therapy use and of invasive breast cancer , ductal carcinoma in situ ( DCIS ) , and estrogen receptor (ER)-positive invasive breast cancer adjusted for age , registry , and time between screening examinations . All statistical tests were two-sided . Between 2000 and 2002 and between 2002 and 2003 , annual rates of postmenopausal hormone therapy use declined by 7 % and 34 % , respectively ( P(trend ) < .001 for both ) . Between 2000 and 2003 , annual rates of invasive cancer declined by 5 % ( P(trend ) = .003 ) . Between 2001 and 2003 , annual rates of ER-positive invasive breast cancer declined by 13 % ( P(trend ) = .002 ) . Rates of DCIS were stable during the study period . Our finding of a statistically significant decline in the rate of ER-positive invasive breast cancer in a screening mammography population after the start of a concomitant substantial decline in postmenopausal hormone therapy use suggests that a decline in screening mammography rates is unlikely to account for the recent decline in US breast cancer incidence BACKGROUND Among women who practice breast self-examination ( BSE ) , breast cancers may be detected when they are at an earlier stage and are smaller than in women who do not practice BSE . However , the efficacy of breast self-examination for decreasing breast cancer mortality is unproven . This study was conducted to determine whether an intensive program of BSE instruction will reduce the number of women dying of breast cancer . METHODS From October 1989 through October 1991 , 266,064 women associated with 519 factories in Shanghai were r and omly assigned to a BSE instruction group ( 132,979 women ) or a control group ( 133,085 women ) . Initial instruction in BSE was followed by reinforcement sessions 1 and 3 years later , by BSE practice under medical supervision at least every 6 months for 5 years , and by ongoing reminders to practice BSE monthly . The women were followed through December 2000 for mortality from breast cancer . Cumulative risk ratios of dying from breast cancer were estimated using Cox proportional hazards models . All statistical tests were two-sided . RESULTS There were 135 ( 0.10 % ) breast cancer deaths in the instruction group and 131 ( 0.10 % ) in the control group . The cumulative breast cancer mortality rates through 10 to 11 years of follow-up were similar ( cumulative risk ratio for women in the instruction group relative to that in the control group = 1.04 , 95 % confidence interval = 0.82 to 1.33 ; P = .72 ) . However , more benign breast lesions were diagnosed in the instruction group than in the control group . CONCLUSIONS Intensive instruction in  BSE did not reduce mortality from breast cancer . Programs to encourage BSE in the absence of mammography would be unlikely to reduce mortality from breast cancer . Women who choose to practice BSE should be informed that its efficacy is unproven and that it may increase their chances of having a benign breast biopsy Context Seven- and 10-year results of the Canadian National Breast Screening Study ( CNBSS ) showed no reduction in breast cancer mortality from five annual mammographies and breast examinations for 40- to 49-year-old women . Some authors have argued that longer follow-up would reveal important benefits . Contribution After 11 to 16 years , the cumulative rate ratios for mammography versus usual care were 0.97 ( 95 % CI , 0.74 to 1.27 ) for breast cancer mortality without adjustment for non study mammography and 1.06 ( CI , 0.80 to 1.40 ) with adjustment . Clinical Implication s The CNBSS suggests that screening 40- to 49-year-old women is unlikely to reduce breast cancer by 20 % or more . Controversy will persist because other studies suggest that screening causes small reductions in breast cancer mortality . The Editors The Canadian National Breast Screening Study -1 ( CNBSS-1 ) , an individually r and omized trial in women 40 to 49 years of age at study entry , evaluated the efficacy of annual mammography , breast physical examination , and instruction on breast self-examination in reducing breast cancer mortality  ( 1 ) . The 7-year ( 2 ) and preliminary 10-year ( 3 ) mortality results were previously reported . At 7 years , 38 women in the mammography group and 28 women in the usual care group had died of breast cancer , for a rate ratio of 1.36 ( 95 % CI , 0.84 to 2.21 ) ( 2 ) . At 10 years , there were 82 breast cancer deaths in the mammography group and 72 in the usual care group ( rate ratio , 1.14 [ CI , 0.83 to 1.56 ] ) ( 3 ) . This article reports CNBSS-1 results after an average 13-year follow-up from study entry . Methods Patient Selection and Recruitment Participants were recruited through media publicity , personal invitation letters using population lists ( municipal registers and provincial health insurance registers ) , group mailings , and physicians ( 4 ) . Eligibility criteria were age 40 to 49 years , no previous diagnosis of breast cancer , not being pregnant , no mammography in the previous 12 months , and signed informed consent . The Human Experimentation Committee of the University of Toronto ( Toronto , Ontario , Canada ) and Human Experimentation Committees at 15 CNBSS collaborating centers approved the study . A total of 50 430 women age 40 to 49 years were enrolled from January 1980 through March 1985 . R and omization Before r and omization , all participants received an initial breast physical examination and instruction on breast self-examination . They were then immediately r and omly assigned to receive mammography and , thereafter , either annual screening with mammography and breast physical examination ( 25 214 women in the mammography group were available for analysis ) or usual care in the context of the Canadian health care system ( 25 216 women in the usual care group were available for analysis ) . Center coordinators r and omly assigned participants using prepared allocation lists , independent of breast physical examination findings . This sequence ensured that the conduct and interpretation of the breast physical examination would be unbiased by knowledge of whether mammography would follow . Intervention Screening Schedule In the mammography group , 62 % of women received five annual screenings . The remainder , recruited later , received four . Each screening examination comprised mammography , breast physical examination , and instruction and evaluation on breast self-examination . Women in the mammography group completed question naires at each rescreening visit . Women in the usual care group were not recalled for rescreening but were mailed annual question naires . We expected that these participants would continue their normal pattern of medical care as delivered through Canada 's universal health care coverage , including access to mammography for diagnosis . Study Procedures Two-view mammography was done on dedicated mammography units ( 5 ) , and second readers review ed mammograms deemed abnormal . Systematic audit procedures were used ( 6 ) . Nurses provided breast physical examination in 12 centers and physicians in 3 centers in Qubec ( 7 ) . These providers taught and evaluated breast self-examination while conducting their own examination ( 8) . If findings on breast physical examination or mammography were abnormal , participants were referred to a CNBSS review clinic . The study surgeon discussed mammography findings with the study radiologist , examined the participant , and decided whether further diagnostic procedures should be recommended to the woman 's physician . The woman 's physician determined whether and how to implement the study surgeon 's recommendations . Data Collection Protocol During the screening period , the center coordinators collected surgery and pathology reports for breast-related diagnostic and therapeutic procedures . The CNBSS pathologists review ed all slides . If the community and CNBSS pathologist disagreed , a panel of three to five CNBSS pathologists blindedly and independently review ed the slides . Extensive quality control procedures were used during data collection . After the screening centers closed in 1988 , the central CNBSS central office annually followed all women known to have breast cancer until 30 June 1996 , the cut-off for this analysis . Passive follow-up of all participants through linkage with the National Cancer Registry identified new diagnoses of breast cancer in study participants through 31 December 1993 . The central office collected pathology reports for postscreening cases of breast cancer . The community diagnosis was accepted for study purpose s. Family members responding to the annual mailed question naire identified deaths that occurred before completion of a participant 's screening schedule . Thereafter , women not known to have cancer were followed only through registry linkage ; their mammography experience was not traced . However , for women known to have breast cancer , attending physicians received annual requests for up date d clinical information , including death .  Attending physicians , who received annual requests for information on women with breast cancer , reported deaths until 30 June 1996 . Linkage with the Canadian Mortality Data base at Statistics Canada ( including deaths in Canadians who resided in the United States at the time of death ) identified causes of death in the entire cohort until 31 December 1993 . The procedures used to verify deaths from breast cancer were described previously ( 2 ) . Investigative procedures were initiated for women dying with breast cancer ; those whose death certificates mentioned breast cancer ; and those whose cause of death 
    Output:
    
Overdiagnosis may have a greater effect on women with shorter life expectancies because of age or comorbid conditions .
From these data , we calculated age-specific rates ( numbers per 1000 women per round ) of invasive