Randomized study of mammography screening — preliminary report on mortality in the stockholm trial (original) (raw)
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JNCI Monographs
The purpose of this overview is to estimate more precisely the long-term effect of mammography screening by adding four more years of follow-up to women aged 40-49 years in the four Swedish trials on mammography screening. Data from the four trials were merged and linked to the Swedish Cancer and Cause of Death Register for 1958-1993 and 1951-1993 respectively to identify date of breast cancer diagnosis and cause and date of death. The invited and control groups comprised 48,569 and 40,247 women respectively. At the December 1993 follow-up, 602 and 482 breast cancer cases were identified in the two groups respectively, of which 104 and 111 had breast cancer as the underlying cause of death. This corresponds to a relative risk (RR) of 0.77 (95% CI: 0.59-1.01) for the two groups. In the 40-44 age group at randomization, 94% of breast cancer patients in the study and 89% in the control group were diagnosed before the age of 50; however, among breast cancer deaths in this age group, only two in the invited and five in the control group died after age 50. At follow-up of women 40-44 years at randomization 208 women in the invited and 184 in the control group were reported to the Cancer registry with breast cancer. Out of these 195 (94%) and 163 (89%) respectively were reported before the age of 50. Further, the relative risk for the age group 40-44 years at randomization by age at follow-up was 1.11, 0.51 and 0.46 for the age groups 45-49, 50-54, and 55-59 at follow-up. This study shows a 23% reduction in the breast cancer mortality in women 40-49 years at randomization achieved from a median trial time of 7.0 years, a median follow-up time of 12.8 years, and a screening interval of 18-24 months. Almost all of the effect in the 40-44 year age group at randomization was due to screening before the age of 50.
Followup after 11 years – update of mortality results in the Stockholm mammographic screening trial
Breast Cancer Research and Treatment, 1997
Results from several randomised mammography screening trials have shown that it is possible to reduce mortality in breast cancer by mammographic screening at least for 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 11 years of followup, to analyse which age group benefits most from screening. In March 1981, 40,318 women in Stockholm, aged 40 through 64 years, entered a randomized trial of breast cancer screening by single view mammography alone, versus no intervention in a control group of 20 000 women. Two screening rounds were performed and the attendance rate was over 80% in the two rounds. During 1986 the control group was invited once to screening. Totally 428 and 217 cases of breast cancer were diagnosed in the study and control groups respectively. After a mean follow-up of 11.4 years a nonsignificant mortality reduction of 26% was observed for the whole study group, with a relative risk (RR) of death in breast cancer of 0.74 (CI(confidence interval) = 0.5-1.1). For women aged 50-64 years a significant 38% mortality reduction was observed with a RR of 0.62 (CI = 0.38-1.0). For women aged 40-49 years no effect on mortality was found, with a RR of death in breast cancer of 1.08 (CI = 0.54-2.17). The breakpoint for benefit in this study seemed to be at 50 years of age when 5-year age groups were analysed, but this tendency is uncertain because of the low statistical power in the analysis of the younger age groups. Long screening intervals, the use of single-view mammography, and the fact that more than 50% of the women in age group 40-49 years were still below 50 years of age when the study was closed, were all facts that could have influenced the results in age group 40-49 years. Larger studies are needed to answer the question whether mammographic screening can be successful in younger age groups.
Journal of medical screening, 1996
To apply an indirect method for estimation of the breast cancer related excess mortality in the Swedish randomised mammography screening trials. Randomised trials on mammography screening have, in Sweden, been performed in the counties of Kopparberg (W) and Ostergötland (E), the so called WE study, and in the three largest cities in Sweden, Stockholm (southern part), Gothenburg, and Malmö. An overview of the trials was presented in the Lancet in 1993 and included 156,911 women in the invited group and 125,866 in the control group. The excess mortality in the breast cancer subgroups was estimated by indirect standardisation using official national cause of death statistics according to Statistics Sweden as a reference. The estimated reduction of the breast cancer related mortality was 24% for the whole group (40-74 years at randomisation). The corresponding figures for the age groups 40-49, 50-59, and 60-69 years were 6%, 28%, and 34% respectively. The results are very similar to tho...
The Gothenburg breast screening trial
Cancer, 1997
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. The authors report on a randomized, controlled trial of mammographic screening for breast carcinoma that was conducted among 51,611 women (21,650 women who were invited to a screening [the study group] and 29,961 women in a control group) ages 39-59 years in Gothenburg, Sweden. Among women in the study group, the screening interval was 18 months. The screening phase of the trial took place in 1982-1991, and follow-up for breast carcinoma mortality continued until December 31, 1996. Mortality from breast carcinoma was analyzed using a Poisson regression model. Overall and age specific effects of invitation to mammography screening on breast carcinoma mortality were calculated. Three mortality effects were estimated: the effect on deaths from breast tumors diagnosed during the screening phase of the trial, as assessed by an independent Endpoint Committee (the EPC evaluation model); the effect on deaths from breast carcinoma diagnosed during the screening phase of the trial, as determined by data from the National Cancer Registry and the National Cause of Death Register (the SCB evaluation model); and the effect on deaths from all breast carcinomas diagnosed up to December 31, 1996, as determined by the National Cancer Registry and the National Cause of Death Register (the SCB follow-up model). A nonsignificant, 21% reduction in the rate of mortality from breast carcinoma with invitation to screening was observed using the EPC evaluation model (relative risk [RR], 0.79; 95% confidence interval [95% CI], 0.58-1.08; P = 0.14); and a borderline significant, 23% rate reduction was observed using the SCB follow-up model (RR, 0.77; 95% CI, 0.60-1.00; P = 0.05). Age specific analyses yielded greater mortality rate reductions for the groups of women ages 39-44 years, 45-49 years, and 55-59 years, but there was no mortality rate reduction in the group of women ages 50-54 years. The effects of invitation to mammographic screening on the incidence of lymph node-positive disease closely paralleled the effects of invitation on breast carcinoma mortality. The effect on breast carcinoma mortality was consistent with the effect on all-cause mortality, suggesting no bias in classification of cause of death. Breast carcinoma incidence in the study group was almost identical to the incidence in the control group after trial by screening had ended in the control group (RR, 0.98; 95% CI, 0.88-1.09; P = 0.7). The current results support the commonly observed 20-30% reduction in breast carcinoma mortality with invitation to screening. The impression that screening is less effective in women younger than 50 years may be an oversimplification. Age specific effects should be a target for further research.
Breast cancer mortality in Copenhagen after introduction of mammography screening: cohort study
British Medical Journal, 2005
Objectives To evaluate the effect on breast cancer mortality during the first 10 years of the mammography service screening programme that was introduced in Copenhagen in 1991. Design Cohort study. Setting The mammography service screening programme in Copenhagen, Denmark. Participants All women ever invited to mammography screening in the first 10 years of the programme. Historical, national, and historical national control groups were used. Main outcome measures The main outcome measure was breast cancer mortality. We compared breast cancer mortality in the study group with rates in the control groups, adjusting for age, time period, and region. Results Breast cancer mortality in the screening period was reduced by 25% (relative risk 0.75, 95% confidence interval 0.63 to 0.89) compared with what we would expect in the absence of screening. For women actually participating in screening, breast cancer mortality was reduced by 37%. Conclusions In the Copenhagen programme, breast cancer mortality was reduced without severe negative side effects for the participants.
Radiology, 2011
From the Departments of Mammography (LT), Surgery (AC), and Pathology (TT), Falun Central Hospital, Falun, Sweden; Department of Mammography, University of Linköping, Linköping, Sweden (BV); Graduate Institute of Epidemiology and Preventive Medicine, National Taiwan ...
The Lancet, 2006
Background The effi cacy of screening by mammography has been shown in randomised controlled trials in women aged 50 years and older, but is less clear in younger women. A meta-analysis of all previous trials showed a 15% mortality reduction in invited women aged 40-49 years at study entry, but this fi nding could be due in part to screening of women after age 50 years. The Age trial was designed to study the eff ect on mortality of inviting women for annual mammography from age 40 years. Methods 160 921 women aged 39-41 years were randomly assigned in the ratio 1:2 to an intervention group of annual mammography to age 48 years or to a control group of usual medical care. The trial was undertaken in 23 NHS breast-screening units in England, Wales, and Scotland. The primary analysis was based on the intention-to-treat principle and compared mortality rates in the two groups at 10 years' follow-up. This study is registered as an International Standard Randomised Controlled Trial, number ISRCTN24647151. Findings At a mean follow-up of 10•7 years there was a reduction in breast-cancer mortality in the intervention group, in relative and absolute terms, which did not reach statistical signifi cance (relative risk 0•83 [95% CI 0•66-1•04], p=0•11; absolute risk reduction 0•40 per 1000 women invited to screening [95% CI-0•07 to 0•87]). Mortality reduction adjusted for non-compliance in women actually screened was estimated as 24% (RR 0•76, 95% CI 0•51-1•01). Interpretation Although the reduction in breast-cancer mortality observed in this trial is not signifi cant, it is consistent with results of other trials of mammography alone in this age-group. Future decisions on screening policy should be informed by further follow-up from this trial and should take account of possible costs and harms as well as benefi ts.
Journal of Medical Screening, 2001
Objectives-To estimate the eVect of the population based service screening programme in Sweden on mortality from breast cancer among women aged 50-69. Setting-In 1986, population based service screening with mammography started in Sweden, and by 1997 screening had been introduced in all counties. Half of the counties invite women from 40 years of age whereas women 50 and older are invited in the other counties. The upper age limit was either 69 or 74. Women in the age group 50-69 years are thus invited to screening in all counties. Methods-The counties which started with mammographic screening in 1986-87 constituted the study group and were compared with the counties which started in 1993 or later. In 1987 the mean number of women aged 50-69 was 161 986 and 98 608 in the study and control groups, respectively. Refined excess mortality (smoothed with the Lowess method) from breast cancer and refined cause specific mortality from breast cancer were used as eVect measures. To adjust for geographical diVerences in mortality from breast cancer a reference period was used. Allowance was made for two potential biases: (a) inclusion bias implying the inclusion of cases diagnosed before invitation to screening in the first screening round, and (b) lead time bias. Results-After a mean follow up time of 10.6 years since the start of screening and a mean individual follow up time of 8.4 years, a non-significant reduction in refined excess mortality for breast cancer was estimated as relative risk (RR) 0.84 (95% confidence interval (95% CI) 0.67 to 1.05). After adjustment for inclusion and lead time biases the RR was 0.80 (20% reduction). Only 27% of the deaths from breast cancer in the total mortality for women aged 50-79 at death consisted of women aged 50-69 at diagnosis who were diagnosed after the start of screening. This figure has important implications for judgement of the impact of screening on age specific national breast cancer mortalities. Conclusions-A non-significant reduction in mortality from breast cancer was found in counties performing service screening with mammography in Sweden. Adjustment for possible biases changed the result towards a larger eVect of screening. The results do not contradict the eVects found in the Swedish randomised mammography trials. (J Med Screen 2001;8:152-160)
2010
Objectives To estimate the absolute numbers of breast cancer deaths prevented and the absolute numbers of tumours overdiagnosed in mammographic screening for breast cancer at ages 50-69 years. Setting The Swedish Two-County randomized trial of mammographic screening for breast cancer, and the UK Breast Screening Programme in England, ages 50-69 years. Methods We estimated the absolute numbers of deaths avoided and additional cases diagnosed in the study group (active study population) of the Swedish Two-County Trial, by comparison with the control group (passive study population). We estimated the same quantities for the mortality and incidence rates in England (1974-2004 and 1974-2003, respectively). We used Poisson regression for statistical inference. Results A substantial and significant reduction in breast cancer mortality was associated with screening in both the Two-County Trial (P , 0.001) and the screening programme in England (P , 0.001). The absolute benefits were estimated as 8.8 and 5.7 breast cancer deaths prevented per 1000 women screened for 20 years starting at age 50 from the Two-County Trial and screening programme in England, respectively. The corresponding estimated numbers of cases overdiagnosed per 1000 women screened for 20 years were, respectively, 4.3 and 2.3 per 1000. Conclusions The benefit of mammographic screening in terms of lives saved is greater in absolute terms than the harm in terms of overdiagnosis. Between 2 and 2.5 lives are saved for every overdiagnosed case.