| 1. |
- Duffy, S, et al.
(author)
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Estimates of overdiagnosis from two trials of mammographic screening for breast cancer
- 2005
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In: Breast Cancer Research. - : Springer Science and Business Media LLC. - 1465-5411 .- 1465-542X. ; 7:6, s. 258-265
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Journal article (peer-reviewed)abstract
- Randomised 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 randomised 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 populations. 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. © 2005 BioMed Central Ltd.
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| 2. |
- Duffy, Stephen W., et al.
(author)
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Absolute numbers of lives saved and overdiagnosis in breast cancer screening, from a randomized trial and from the Breast Screening Programme in England
- 2010
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In: Journal of Medical Screening. - : Royal Society of Medicine. - 0969-1413 .- 1475-5793. ; 17:1, s. 25-30
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Journal article (peer-reviewed)abstract
- 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 (Pless than0.001) and the screening programme in England (Pless than0.001). 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.
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| 3. |
- Hofvind, S., et al.
(author)
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Influence of review design on percentages of missed interval breast cancers : Retrospective study of interval cancers in a population-based screening program
- 2005
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In: Radiology. - : Radiological Society of North America (RSNA). - 0033-8419 .- 1527-1315. ; 237:2, s. 437-443
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Journal article (peer-reviewed)abstract
- PURPOSE: To retrospectively investigate whether different review designs have an influence on the estimate of missed interval cancer in a population-based breast cancer screening program. MATERIALS AND METHODS: The Norwegian Breast Cancer Screening Program invites women aged 50-69 years to undergo biennial screening mammography. The current study was part of the evaluation and scientific aspects of the screening program and thus was covered by the general ethical approval of the screening program as a part of the Cancer Registry of Norway. All participants signed an informed consent that specified that data related to their screening visit could be used for evaluation and scientific purposes. Six radiologists (9-34 years of experience in mammography) reviewed previously obtained bilateral two-view screening and diagnostic mammograms of 231 interval cancers, 117 screening-detected cancers, and 373 normal cases. Four review designs were used: individual and paired blinded review and individual and consensus informed review. A five-point interpretation scale was used to reclassify the cancers into missed cancers, minimal signs, and true cancers. The number and proportion of subgroups were estimated with 95% confidence intervals. RESULTS: Of 231 interval cancers, 46 (19.9%) were reclassified as missed cancers with the mixed blinded individual review and 54 (23.4%) were classified as missed cancers with the mixed blinded paired review. Eighty-three cancers (35.9%) were classified as missed cancers with individual informed review, and 78 (33.8%) were classified as missed cancers with consensus informed review. Thirty-nine cancers (16.8%) were reclassified as missed when four or more radiologists assigned a score of 2 or more (probably benign or more suspicious), three cancers (1.3%) were reclassified as missed when a score of 4 or more (probably malignant or more suspicious) was assigned. CONCLUSION: The percentage of interval cancers classified as missed ranged from 1.3% to 35.9% according to review design. To encourage learning, a review protocol should include both blinded and informed designs. © RSNA, 2005.
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| 4. |
- Numan Hellquist, Barbro, et al.
(author)
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Effectiveness of population-based service screening with mammography for women ages 40 to 49 years : evaluation of the Swedish Mammography Screening in Young Women (SCRY) cohort
- 2011
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In: Cancer. - : Wiley-Blackwell. - 0008-543X .- 1097-0142. ; 117:4, s. 714-722
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Journal article (peer-reviewed)abstract
- BACKGROUND: The effectiveness of mammography screening for women ages 40 to 49 years still is questioned, and few studies of the effectiveness of service screening for this age group have been conducted.METHODS: Breast cancer mortality was compared between women who were invited to service screening at ages 40 to 49 years (study group) and women in the same age group who were not invited during 1986 to 2005 (control group). Together, these women comprise the Mammography Screening of Young Women (SCRY) cohort, which includes all Swedish counties. A prescreening period was defined to facilitate a comparison of mortality in the absence of screening. The outcome measure was refined mortality, ie, breast cancer death for women who were diagnosed during follow-up at ages 40 to 49 years. Relative risks (RRs) with 95% confidence intervals (CIs) were estimated.RESULTS: There was no significant difference in breast cancer mortality during the prescreening period. During the study period, there were 803 breast cancer deaths in the study group (7.3 million person-years) and 1238 breast cancer deaths in the control group (8.8 million person-years). The average follow-up was 16 years. The estimated RR for women who were invited to screening was 0.74 (95% CI, 0.66-0.83), and the RR for women who attended screening was 0.71 (95% CI, 0.62-0.80).CONCLUSIONS: In this comprehensive study, mammography screening for women ages 40 to 49 years was efficient for reducing breast cancer mortality.
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| 5. |
- Tabar, Laszlo, et al.
(author)
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Swedish Two-County Trial: Impact of Mammographic Screening on Breast Cancer Mortality during 3 Decades
- 2011
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In: Radiology. - : Radiological Society of North America (RSNA). - 0033-8419 .- 1527-1315. ; 260:3, s. 658-663
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Journal article (peer-reviewed)abstract
- Purpose: To estimate the long-term (29-year) effect of mammographic screening on breast cancer mortality in terms of both relative and absolute effects. less thanbrgreater than less thanbrgreater thanMaterials and Methods: This study was carried out under the auspices of the Swedish National Board of Health and Welfare. The board determined that, because randomization was at a community level and was to invitation to screening, informed verbal consent could be given by the participants when they attended the screening examination. A total of 133 065 women aged 40-74 years residing in two Swedish counties were randomized into a group invited to mammographic screening and a control group receiving usual care. Case status and cause of death were determined by the local trial end point committees and, independently, by an external committee. Mortality analysis was performed by using negative binomial regression. less thanbrgreater than less thanbrgreater thanResults: There was a highly significant reduction in breast cancer mortality in women invited to screening according to both local end point committee data (relative risk [RR] = 0.69; 95% confi dence interval: 0.56, 0.84; P andlt;.0001) and consensus data (RR = 0.73; 95% confi dence interval: 0.59, 0.89; P =.002). At 29 years of follow-up, the number of women needed to undergo screening for 7 years to prevent one breast cancer death was 414 according to local data and 519 according to consensus data. Most prevented breast cancer deaths would have occurred (in the absence of screening) after the first 10 years of follow-up. less thanbrgreater than less thanbrgreater thanConclusion: Invitation to mammographic screening results in a highly significant decrease in breast cancer-specific mortality. Evaluation of the full impact of screening, in particular estimates of absolute benefit and number needed to screen, requires follow-up times exceeding 20 years because the observed number of breast cancer deaths prevented increases with increasing time of follow-up.
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| 6. |
- Vitak, Bedrich
(author)
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Interval cancers, positive predictive value for malignance and other early quality indicators in mammographic screening for breast cancer
- 1998
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Doctoral thesis (other academic/artistic)abstract
- The study was designed to evaluate early quality indicators in screening for breast cancer. lt comprised, (i) investigations of compliance, recall, referral, cancer detection, and interval cancer rates in the Östergötland screening programme of women aged 40-74 years; (ii) evaluation of the three-stage diagnostic procedure for pre-operative assessment of women with suspicious mammographic findings; (iii) comprehensive analysis of all invasive interval cancers detected; and (iv) investigation into how to reduce the number of interval cancers without a concomitant increase in false positives.The attendance rates were 85.5% at the initial screen and 81.3% at subsequent screens. The referral rates for further examination at subsequent screens were roughly half of th'lt at the initial screen. The cancer detection rates were 6.4/1000 at the initial and 2.6/1000 at subsequent screens. The positive predictive value for malignancy at surgery was 96% for ages 50-74 years. Apart from the tumour grade (not analysed) the diagnostic outcome tallied with the quality targets stipulated by Tabár et al.The study confirmed the less favourable prognosis for interval cancer patients and cancers in non-attenders compared to screen-detected patients, but the mode of detection was not an independent predictor of metastatic capacity (hazard rate ratio [RR] of distant recurrence /adjusted for other variables/ RR=1.39, 95%confidence interval [95%CI] 0.78-2.46 for interval cancers; and RR=1.6, 95%CI 0.76-3.36 for non-attenders). The higher metastatic potential in these tumours could be explained by the differences in tumour characteristics at the time of diagnosis.The incidence risk of interval cancer was 0.46/1000 for tumours detected within 1 year of the latest screen, and 1.2/1000 for tumours detected within 2 years of the latest screen. Despite the lower age-specific breast cancer incidence in women aged 40-49 years, these women ran roughly the same risk of interval cancer after a negative screen as did the other age groups in the screening programme.Patients with potential iatrogenic delay in diagnosis (overlooked or misinterpreted cancers) constituted 25% of all patients with invasive interval cancer, and patients with true interval cancer 49%. The radiological category of interval cancer had no significant influence on the survival (overall comparison, p=0.1202; comparison of true interval with missed interval cancers, p=0.3175). In the present study there was no clear evidence of difference in prognosis between true interval and overlooked or misinterpreted interval cancers.The interval between the latest screen and diagnosis was not an independent prognostic factor in patients with true interval cancers (RR=0.47, 95%CI 0.16-1.35 for tumours detected 21 year after the latest screen), and there was no significant difference in survival according to this interval (comparison of tumours detected <1 year with tumours detected 21 year of the latest screen, p=0.3844).The study confirmed the association of criteria for referral for further examination with number of false positives. Efforts to reduce the number of interval cancers by lowering the mammographic threshold for recall are likely to be counterproductive. The early quality indicators constitute. an excellent means of monitoring of the quality of screening.
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