***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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    ***EXAMPLES*** 
    Input: Results from the r and omized trial conducted by the Health Insurance Plan ( HIP ) to determine the efficacy of breast cancer screening with mammography and palpation are reported for longer periods than previously available . By the end of 10 years after entry , the study group 's  mortality due to breast cancer was about 30 % below the control group 's . Arithmetic gains due to screening were maintained through year 14 ; relative gains declined . With increases in the period of follow-up , cumulative survival rates among cases detected by mammography alone ( palpation negative during screening ) , decreased more rapidly than rates among other subgroups , but survival rates for mammography cases remained relatively high . Study women aged 40 - 49 years at entry began to show lower breast cancer mortality than those in the control group as duration of follow-up increased . Reservations are advanced about the acceptance of this finding as evidence of the efficacy of screening under age 50 under the conditions of the HIP study . The reservations are based on the observation that the decrease of mortality among the study group aged 45 - 49 at entry is concentrated entirely among cases diagnosed after they reached 50 years of age A trial in the UK to study the effect on mortality from breast cancer of invitation for annual mammography from the age of 40–41 , has r and omised a total of 160 921 women in the ratio 1 : 2 to the intervention and control arms . All breast cancers diagnosed in the two arms have been identified , and the histology review ed . This paper presents the results of an interim analysis using surrogate outcome measures to compare predicted breast cancer mortality in the two arms based on 1287 cases diagnosed to 31.12.1999 . Due to earlier diagnosis , there is currently an 8 % excess of invasive breast cancers in the intervention arm . The ratio of predicted deaths at 10 years in the intervention arm relative to the control arm , adjusted for this excess diagnosis , ranges from 0.89 ( 95 % confidence interval ( CI ) 0.78–1.01 ) to 0.90 ( 95 % CI 0.80–1.01 ) . Screening from age 40 may result in a lower reduction in breast cancer mortality than that observed in other trials including women below age 50 . This analysis based on surrogate outcome measures suggests that a reduction in breast cancer mortality may be observed in this trial . However , a number of assumptions have been necessary and firm conclusions must await the analysis of observed mortality from breast cancer The Canadian National Breast Screening Study ( CNBSS ) , conducted on women age 40 - 49 , was design ed to evaluate the efficacy of combined annual mammography and physical examination of the breasts in reducing breast cancer mortality in comparison to usual care ( UC ) controls . From January 1980 through March 1985 , 25,214 women were individually r and omized to the mammography/physical exam ( MP ) arm and 25,216 to the UC .  The integrity of the r and omization has been review ed and confirmed to be unbiased . During an average , follow-up of 10.5 years from entry ( range : 8.75 - 13 years ) , 82 women died from breast cancer in the MP arm and 72 in the UC , for a rate ratio of 1.14 ( 95 % confidence interval : 0.83 - 1.56 ) . All-cause mortality was almost identical comparing the two groups ; the nonsignificant excess of breast cancer deaths in the MP arm was balanced by an excess of other cancer deaths in the UC arm Debate continues over the effectiveness of screening by mammography in women below age 50 . We report here on results of screening in the first 10 years of a r and omised trial to study the effect on breast cancer mortality of  invitation to annual mammography  from age 40 to 41 compared to first invitation to the 3-yearly  UK national programme  at age 50–52 . The trial is taking place in 23 NHS breast screening centres . Between 1991 and 1997 , 160 921 women were r and omised in the ratio 1 : 2 to intervention and control arms . Screening is by two views at first screen and single view subsequently ; data on screening up to and including round five are now complete . Uptake of invitation to screening is between 68 and 70 % at all but the latest screening rounds . Rates of referral for assessment are 4.6 % at first screen and 3.4 % at subsequent screens . Invasive cancer detection rates are 0.09 % at first screen , and similar at rescreens until the sixth and later screens . There is little evidence of regular mammography in the trial control arm . The setting of this trial within the NHS breast screening programme should ensure applicability of results to a national programme OBJECTIVES To evaluate the efficacy of the combination of annual screening with mammography , physical examination of the breasts and the teaching of breast self-examination in reducing the rate of death from breast cancer among women aged 40 to 49 years on entry . DESIGN Individually r and omized controlled trial . SETTING Fifteen urban centres in Canada with expertise in the diagnosis and treatment of breast cancer . PARTICIPANTS Women with no history of breast cancer and no mammography in the previous 12 months were r and omly assigned to undergo either  annual mammography and physical examination ( MP group ) or usual care after an initial physical examination ( UC group ) . The 50,430 women enrolled from January 1980 through March 1985 were followed for a mean of 8.5 years . DATA COLLECTION Derived from the participants by initial and annual self-administered question naires , from the screening examinations , from the patients ' physicians , from the provincial cancer registries and by record linkage to the Canadian National Mortality Data Base . Expert panels evaluated histologic and death data . MAIN OUTCOME MEASURES Rates of referral from screening , rates of detection of breast cancer from screening and from community care , nodal status , tumour size , and rates of death from all causes and from breast cancer . RESULTS Over 90 % of the women in each group attended the screening sessions or returned the annual question naires , or both , over years 2 to 5 . The characteristics of the women in the two groups were similar . Compared with the Canadian population , the participants were more likely to be married , have fewer children , have more education , be in a professional occupation , smoke less and have been born in North America . The rate of screen-detected breast cancer on first examination was 3.89 per 1000 in the MP group and 2.46 per 1000 in the UC group ; more node-positive tumours were found in the MP group than in the UC group . During years 2 through 5 the ratios of observed to expected cases of invasive breast cancer were 1.26 in the MP group and 1.02 in the UC group . Of the women with invasive breast cancer through to 7 years , 191 and 157 women in the MP and UC groups respectively had no node involvement , 55 and 43 had one to three nodes involved , 47 and 23 had four or more nodes involved , and 38 and 49 had an unknown nodal status . There were 38 deaths from breast cancer in the MP group and 28 in the UC group . The ratio of the proportions of death from breast cancer in the MP group compared with those in the UC group was 1.36 ( 95 % confidence interval 0.84 to 2.21 ) . The survival rates were similar in the two groups . The highest survival rate occurred among women whose cancer had been detected by mammography alone . CONCLUSION The study was internally valid , and there was no evidence of r and omization bias . Screening with yearly mammography and physical examination of the breasts detected considerably more node-negative , small tumours than usual care , but it had no impact on the rate of death from breast cancer up to 7 years ' follow-up from entry BACKGROUND As mammographic screening becomes more widespread , larger numbers of tumours are diagnosed while small and node negative . METHODS We examined detection mode , tumour size , node status , histological type , therapy and outcome in 1053 breast cancers diagnosed in one county of the Swedish Two-County Trial of mammographic screening for breast cancer . RESULTS Of patients undergoing total mastectomy with axillary dissection  , 65 % were found to be node negative . For tumours of size 1 - 9 mm , 95 % were node negative . The major effects on survival were tumour size , node status and histological type .  Primary adjuvant therapy had no significant association with survival . CONCLUSIONS The advent of mammography has substantially enhanced the possibilities for less radical treatment . There is an urgent need for therapeutic trials utilizing mammographic-pathological correlations to ascertain in advance which tumours can and which can not benefit from more radical therapy 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 19 
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This could be because screening was better in some trials than in others at advancing the time of diagnosis .
If so , more cancers would be identified in such trials relative to the control group , and fewer of the cancers would have reached an advanced stage .
Consequently , the differences in the reported reductions in breast cancer mortality can not be explained by differences in screening effectiveness .
Given that the size of the bias was similar to the estimated screening effect , screening appeared ineffective