Swedish Organised Service Screening Evaluation Group. Reduction in breast cancer mortality from the organised service screening with mammography: 2. Validation with alternative analytic methods

Plasma Levels of CXC Motif Chemokine 1 (CXCL1) and Chemokine 8 (CXCL8) as Diagnostic Biomarkers in Luminal A and B Breast Cancer

Chemokines are involved in the regulation of immune balance and in triggering an immune response. CXCL1 and CXCL8 belong to the ELR-motif-containing group of CXC chemokines, which, in breast cancer (BC), stimulate angiogenesis and increase migration and invasiveness of tumor cells. The aim of this study was to evaluate CXCL1, CXCL8 and comparative marker CA 15-3 plasma concentrations in BC patients with luminal subtypes A and B. The study group consisted of 100 patients with BC, and the control group of 50 subjects with benign breast lesions and 50 healthy women. Chemokines concentrations were determined by ELISA method; CA15-3-by CMIA. Concentrations of CXCL8 and CA15-3 were significantly higher in BC total group and luminal B (for CA15-3 also in luminal A) subtype of BC than in healthy controls and subjects with benign lesions. In the total BC group, the highest SE, PPV and NPV were observed for CXCL8 (70%, 77.78%, 50%, resp.). A combined analysis of tested chemokines with CA 15-3 increased SE and NPV values (96%, 69.23%, resp.). The diagnostic power of the test (measured by area under ROC curve (AUC)) showed the highest value for CXCL8 in the total BC group (0.6410), luminal A (0.6120) and B subgroup of BC (0.6700). For the combined parameter, the AUC was increasing and reached the highest value for CXCL1 + CXCL8 + CA15-3 combination (0.7024). In light of these results, we suggest that CXCL8 could be used as an additional diagnostic marker that would positively influence the diagnostic utility of CA 15-3, especially in luminal B subtype of BC.

Fully automatic classification of automated breast ultrasound (ABUS) imaging according to BI-RADS using a deep convolutional neural network

PURPOSE

The aim of this study was to develop and test a post-processing technique for detection and classification of lesions according to the BI-RADS atlas in automated breast ultrasound (ABUS) based on deep convolutional neural networks (dCNNs).

METHODS AND MATERIALS

In this retrospective study, 645 ABUS datasets from 113 patients were included; 55 patients had lesions classified as high malignancy probability. Lesions were categorized in BI-RADS 2 (no suspicion of malignancy), BI-RADS 3 (probability of malignancy < 3%), and BI-RADS 4/5 (probability of malignancy > 3%). A deep convolutional neural network was trained after data augmentation with images of lesions and normal breast tissue, and a sliding-window approach for lesion detection was implemented. The algorithm was applied to a test dataset containing 128 images and performance was compared with readings of 2 experienced radiologists.

RESULTS

Results of calculations performed on single images showed accuracy of 79.7% and AUC of 0.91 [95% CI: 0.85-0.96] in categorization according to BI-RADS. Moderate agreement between dCNN and ground truth has been achieved (κ: 0.57 [95% CI: 0.50-0.64]) what is comparable with human readers. Analysis of whole dataset improved categorization accuracy to 90.9% and AUC of 0.91 [95% CI: 0.77-1.00], while achieving almost perfect agreement with ground truth (κ: 0.82 [95% CI: 0.69-0.95]), performing on par with human readers. Furthermore, the object localization technique allowed the detection of lesion position slice-wise.

CONCLUSIONS

Our results show that a dCNN can be trained to detect and distinguish lesions in ABUS according to the BI-RADS classification with similar accuracy as experienced radiologists.

KEY POINTS

• A deep convolutional neural network (dCNN) was trained for classification of ABUS lesions according to the BI-RADS atlas. • A sliding-window approach allows accurate automatic detection and classification of lesions in ABUS examinations.

Finite element model of mechanical imaging of the breast

Purpose: Malignant breast lesions can be distinguished from benign lesions by their mechanical properties. This has been utilized for mechanical imaging in which the stress distribution over the breast is measured. Mechanical imaging has shown the ability to identify benign or normal cases and to reduce the number of false positives from mammography screening. Our aim was to develop a model of mechanical imaging acquisition for simulation purposes. To that end, we simulated mammographic compression of a computer model of breast anatomy and lesions. Approach: The breast compression was modeled using the finite element method. Two finite element breast models of different sizes were used and solved using linear elastic material properties in open-source virtual clinical trial (VCT) software. A spherical lesion (15 mm in diameter) was inserted into the breasts, and both the location and stiffness of the lesion were varied extensively. The average stress over the breast and the average stress at the lesion location, as well as the relative mean pressure over lesion area (RMPA), were calculated. Results: The average stress varied 6.2-6.5 kPa over the breast surface and 7.8-11.4 kPa over the lesion, for different lesion locations and stiffnesses. These stresses correspond to an RMPA of 0.80 to 1.46. The average stress was 20% to 50% higher at the lesion location compared with the average stress over the entire breast surface. Conclusions: The average stress over the breast and the lesion location corresponded well to clinical measurements. The proposed model can be used in VCTs for evaluation and optimization of mechanical imaging screening strategies.

Mammography Screening and Research Evidence: The Swedish Contribution

Sweden has made a contribution to mammography screening research considerably disproportionate to its size. With 0.13% of the world's population, Sweden contributed almost half of the randomized trial evidence on mammography screening. In addition to the fundamental efficacy of screening in preventing deaths from breast cancer, Swedish researchers have produced a considerable volume of research evaluating mammography screening in the routine healthcare services setting and illuminating issues of breast cancer progression and natural history. The basic result that screening prevents deaths from breast cancer has informed policy and led to substantial preservation of life internationally.

Worldwide Review and Meta-Analysis of Cohort Studies Measuring the Effect of Mammography Screening Programmes on Incidence-Based Breast Cancer Mortality

In 2012, the Euroscreen project published a review of incidence-based mortality evaluations of breast cancer screening programmes. In this paper, we update this review to October 2019 and expand its scope from Europe to worldwide. We carried out a systematic review of incidence-based mortality studies of breast cancer screening programmes, and a meta-analysis of the estimated effects of both invitation to screening and attendance at screening, with adjustment for self-selection bias, on incidence-based mortality from breast cancer. We found 27 valid studies. The results of the meta-analysis showed a significant 22% reduction in breast cancer mortality with invitation to screening, with a relative risk of 0.78 (95% CI 0.75-0.82), and a significant 33% reduction with actual attendance at screening (RR 0.67, 95% CI 0.61-0.75). Breast cancer screening in the routine healthcare setting continues to confer a substantial reduction in mortality from breast cancer.

Effect of organized mammography screening on breast cancer mortality: A population-based cohort study in Norway

We aimed to estimate the effect of organized mammography screening on incidence-based breast cancer mortality by comparing changes in mortality among women eligible for screening to concurrent changes in younger and older ineligible women. In a county-wise balanced, open-cohort study, we used birth cohorts (1896-1982) to construct three age groups in both the historical and screening period: women eligible for screening, and younger or older women ineligible for screening. We included women diagnosed with breast cancer who died within the same age-period group during 1987-2010 (n = 4,903). We estimated relative incidence-based mortality rate ratios (relative MRR) comparing temporal changes in eligible women to concurrent changes in ineligible women. Additionally, we conducted analyses comparing the change in eligible women to younger, ineligible women with either continued accrual and follow-up period (eligible women only) or continued follow-up period. All three age groups experienced a reduction in mortality, but the decrease among eligible women was about the same among ineligible women (relative MRR = 1.05, 95% CI: (0.94-1.18)). Varying the definition of follow-up yielded similar results. Mammography screening was not associated with a larger breast cancer mortality reduction in women eligible relative to ineligible women.

Emerging Breast Imaging Technologies on the Horizon

Early detection of breast cancers by mammography in conjunction with adjuvant therapy has contributed to reduction in breast cancer mortality. Mammography remains the "gold-standard" for breast cancer screening but is limited by tissue superposition. Digital breast tomosynthesis and more recently, dedicated breast computed tomography have been developed to alleviate the tissue superposition problem. However, all of these modalities rely upon x-ray attenuation contrast to provide anatomical images, and there are ongoing efforts to develop and clinically translate alternative modalities. These emerging modalities could provide for new contrast mechanisms and may potentially improve lesion detection and diagnosis. In this article, several of these emerging modalities are discussed with a focus on technologies that have advanced to the stage of in vivo clinical evaluation.

Aberrant promoter methylation of cancer-related genes in human breast cancer

The clinical relevance of aberrant DNA methylation is being increasingly recognized in breast cancer. The present study aimed to evaluate the promoter methylation status of seven candidate genes and to explore their potential use as a biomarker for the diagnosis of breast cancer. A total of 70 Chinese patients with breast cancer were recruited, and matched with 20 patients with benign breast disease (BBD). Methylation-specific polymerase chain reaction was performed to measure the methylation status of selected genes. The protein expression of candidate genes was determined by immunohistochemistry. Hypermethylation of Breast cancer 1, early onset; DNA repair associated (BRCA1), glutathione S-transferase pi 1 (GSTP1), cyclin dependent kinase inhibitor 2A, O-6-methylguanine-DNA methyltransferase, phosphatase and tensin homolog, retinoic acid receptor beta 2 and cyclin D2 was observed to be more common in cancerous tissues (24.3, 31.4, 40.0, 27.1, 48.6, 55.7 and 67.1%, respectively) as compared with BBD controls (0.0, 0.0, 20.0, 25.0, 40.0, 40.0 and 45.0%, respectively). Immunohistochemical analysis demonstrated a correlation between the methylation of the target gene and downregulation of protein expression. When BRCA1 and GSTP1 were combined as the biomarker, the area under the receiver operating characteristic curve reached 0.721 (95% confidence interval, 0.616–0.827). The present findings indicated that promoter methylation of cancer-related genes was frequently observed in patients with breast cancer and was associated with various clinical features. Hypermethylation of BRCA1 and GSTP1 may be used as promising biomarkers for breast cancer.

What Information Should be Given to Women Invited for Mammographic Screening for Breast Cancer?

Mammography is the only proven frontline screening method for breast cancer. Following the demonstration of a reduction in breast cancer mortality with mammography, population mammographic screening services have been instituted, and there has been discussion in the medical literature of how to convey the pros and cons of screening to invited women. Much of the discussion has focused on the negative aspects of screening, such as false-positive and negative screens, overdiagnosis and anxiety. Also, some commentators have advocated rather cumbersome amounts of quantitative information. In this article we review the original evidence on the positive and negative aspects of screening, and show that the latter may have been exaggerated in the past. We suggest a few simple and clear points that should be made to the invited women, summarizing the positive and negative aspects without a mass of confusing statistics.

Digital Breast Tomosynthesis: State of the Art

This topical review on digital breast tomosynthesis (DBT) is provided with the intent of describing the state of the art in terms of technology, results from recent clinical studies, advanced applications, and ongoing efforts to develop multimodality imaging systems that include DBT. Particular emphasis is placed on clinical studies. The observations of increase in cancer detection rates, particularly for invasive cancers, and the reduction in false-positive rates with DBT in prospective trials indicate its benefit for breast cancer screening. Retrospective multireader multicase studies show either noninferiority or superiority of DBT compared with mammography. Methods to curtail radiation dose are of importance. (©) RSNA, 2015.

Correction factors for self-selection when evaluating screening programmes

Objective

In screening programmes there is recognized bias introduced through participant self-selection (the healthy screenee bias). Methods used to evaluate screening programmes include Intention-to-screen, per-protocol, and the “post hoc” approach in which, after introducing screening for everyone, the only evaluation option is participants versus non-participants. All methods are prone to bias through self-selection. We present an overview of approaches to correct for this bias.

Methods

We considered four methods to quantify and correct for self-selection bias. Simple calculations revealed that these corrections are actually all identical, and can be converted into each other. Based on this, correction factors for further situations and measures were derived. The application of these correction factors requires a number of assumptions.

Results

Using as an example the German Neuroblastoma Screening Study, no relevant reduction in mortality or stage 4 incidence due to screening was observed. The largest bias (in favour of screening) was observed when comparing participants with non-participants.

Conclusions

Correcting for bias is particularly necessary when using the post hoc evaluation approach, however, in this situation not all required data are available. External data or further assumptions may be required for estimation.

Breast cancer screening halves the risk of breast cancer death: a case-referent study

Large-scale epidemiologic studies have consistently demonstrated the effectiveness of mammographic screening programs, however the benefits are still subject to debate. We estimated the effect of the Dutch screening program on breast cancer mortality. In a large multi-region case-referent study, we identified all breast cancer deaths in 2004 and 2005 in women aged 50-75 who had been invited for screening (cases). Cases were individually matched to referents from the population invited to screening. Conditional logistic regression was used to estimate the odds ratio (OR) of breast cancer death according to individual screening history. The OR was adjusted for self-selection bias using regional correction factors for the difference in baseline risk for breast cancer death between screened and unscreened women. A total of 1233 cases and 2090 referents were included in this study. We found a 58% reduction in breast cancer mortality in screened versus unscreened women (adjusted OR = 0.42, 95% CI 0.33-0.53). Screening, i.e. early detection and treatment, has resulted in a substantial reduction in breast cancer mortality, indicating that the Dutch breast cancer screening program is highly effective.

Multifocal breast cancer documented in large-format histology sections: long-term follow-up results by molecular phenotypes

BACKGROUND

The prognostic significance of molecular phenotype in breast cancer is well established in the literature. Recent studies have demonstrated that subgross lesion distribution (unifocal, multifocal, and diffuse) and disease extent also carry prognostic significance in this disease. However, the correlation of molecular phenotypes with subgross parameters has not yet been investigated in detail.

METHODS

In total, 444 consecutive invasive breast cancers that were documented in large-format histology slides and worked up with detailed radiologic-pathologic correlation were sampled into tissue microarray blocks and stained immunohistochemically to delineate the molecular subtypes.

RESULTS

Diffuse or multifocal distribution of the invasive component of breast carcinomas in this series was associated with a 4.14-fold respectively 2.75-fold risk of cancer-related death compared with unifocal tumors irrespective of molecular phenotype. Patients who had human epidermal growth factor receptor 2 (HER2)-positive cancers; estrogen receptor-negative, progesterone receptor-negative, and HER2-negative (triple-negative) cancers; or basal-like cancers had a 2.18-fold, 2.33-fold, and 4.07-fold risk of dying of disease, respectively, compared with patients who had luminal A carcinomas. Unifocal luminal A, HER2-positive, and basal-like cancers were associated with significantly better long-term survival outcomes than their multifocal or diffuse counterparts; luminal B and triple-negative tumors also had the same tendency. In multivariate analysis, patient age, tumor size category, lymph node status, lesion distribution, and molecular phenotypes remained significant.

CONCLUSIONS

Multifocality and diffuse distribution of the invasive component were associated with significantly poorer survival in women with breast carcinomas compared with unifocal disease in patients with luminal A, HER2 type, and basal-like cancers. Molecular classification of breast cancer is a powerful tool but gains in power when combined with conventional and subgross morphologic parameters.

Stage-specific breast cancer incidence rates among participants and non-participants of a population-based mammographic screening program

The Norwegian Breast Cancer Screening Program was rolled out county by county over the course of a decade, from 1996 to 2005, and now encompasses all Norwegian women aged 50-69 years. We aim to compare DCIS and stage-specific invasive breast cancer incidence rates among participants, non-participants, and women not yet invited to the screening program over this entire implementation period. We estimate stage-specific breast tumor incidence rates for 640,347 women 50-69 years of age invited to the screening program between 1996 and 2007. We compare incidence rates and stage distribution among women diagnosed with breast cancer who were invited and participated, invited but not participated, and women not yet invited to the screening program using two-sided Chi-squared tests to determine statistical significance between groups. The incidence of ductal carcinoma in situ (DCIS) was 3.0 times higher and invasive breast cancer was 1.5 times higher for invited participants compared to invited non-participants (p < 0.001). While the incidence of Stage I cancer was two times higher among participants compared to non-participants (p < 0.001), the incidences of Stages III and IV cancer were two and three times lower, respectively, among participants compared to non-participants (p < 0.001 for both). No significant differences in stage-specific incidence or treatment utilization rates were observed between invited non-participants and not yet invited women, except for stage IV cancers, which were detected at a higher rate among women who were not yet invited (7.5 vs. 4.6 %, p = 0.001). Compared with women invited who did not participate, participants in the screening program are more likely to be diagnosed with DCIS and early stage invasive breast cancer and are less likely to be diagnosed with advanced stage breast cancer. More research is required to determine whether these differences in stage-specific incidences among invited participants and non-participants are associated with differences in mortality rates.

Differentiation between benign and malignant breast tumors using kinetic features of real-time harmonic contrast-enhanced ultrasound

BACKGROUND

Contrast-enhanced ultrasound (CEUS) has gained interest because of its ability to gather vascular information in diverse organs. There is still a subject of debate concerning its value in breast lesions, especially as a differential diagnostic tool.

PURPOSE

To investigate whether kinetic parameters of CEUS can differentiate between malignant and benign breast lesions.

MATERIAL AND METHODS

We evaluated 75 malignant and 21 benign lesions in the breast or axilla. Contrast harmonic imaging (CHI) US was performed after the injection of a bolus dose of 2.4 mL of Sono Vue® (Bracco, Milano, Italy). The following parameters were calculated for kinetic analysis: initial slope, time to peak enhancement, wash-out ratios W(21) and W(50) (relative decrease in signal intensity from the peak enhancement to 21 s and 50 s, respectively).

RESULTS

A significant difference was found between the benign and malignant lesions in time-to-peak (P value <0.05) and wash-out ratios W(21) (P value <0.001) and W(50) (P value <0.001). The mean time-to-peak was 9.3 s for malignant and 14.6 s for benign lesions. The mean signal drop from peak to signal intensity measured at 50 s was 85% for malignant and 66% for benign lesions. There was no difference in absolute values of peak signal intensity and initial slope. The most significant difference between standardized benign and malignant wash-out curves was found at 21 s but statistical significance was reached in the range of 14-50 s.

CONCLUSION

Real-time CEUS can evolve into a new non-invasive option for differentiate malignant from benign breast lesions.

Balancing harms and benefits of service mammography screening programs: a cohort study

INTRODUCTION

The use of screening mammography is still under debate within the medical community. The aim of this study is to define a balance sheet of benefits (breast cancer mortality reduction) and harms (overdiagnosis) for mammography screening programs.

METHODS

We compared breast cancer incidence and mortality in two cohorts of women, defined as 'attenders' or 'non-attenders' on the basis of the individual attitudes towards screening, who were invited to the first round of the Florentine screening program. The effects of screening exposure on breast cancer incidence and mortality were evaluated by fitting Poisson regression models adjusted for age at entry, marital status and deprivation index. We performed a sensitivity analysis excluding 34 women not responding to the invitation with a breast cancer diagnosis in the following six months.

RESULTS

In total, we included 51,096 women aged 50 to 69 years invited at the first screening round (1991 to 1993) and followed-up for breast cancer incidence and mortality until 31 December 2007 and 31 December 2008, respectively The estimate of mortality reduction varies from 45% among 50 to 59 year-old women up to 51% among 60 to 69 year-old women. The estimate of overdiagnosis, according to the cumulative-incidence method, is an additional 10% of all breast cancer cases among 60 to 69 year-old women screened.

CONCLUSIONS

Comparing the breast cancer mortality and breast cancer incidence between attenders and non-attenders, we have determined that the overall cost to save one life corresponds to no more than one over-diagnosed tumor (from 0.6 to 1 depending on the selection criteria of the cohort), even if a residual self-selection bias cannot be excluded.

Minor influence of self-selection bias on the effectiveness of breast cancer screening in case-control studies in the Netherlands

Background

Self-selection bias is considered to be a problem when evaluating the effectiveness of breast cancer service screening in case-control studies.

Objective

Using the incidence-based mortality method (IBM), a correction factor for the potential influence of self-selection can be derived from a group of non-screened women and a group of not-invited women.

Methods

Breast cancer patients, diagnosed in 1990–1995 and between the ages of 50 to 70, were selected from the Netherlands Cancer Registry and five screening regions in the Netherlands. Person-years were calculated for non-screened and not-invited women by using population data available on the number of women invited, the number of women screened and the total population. Incidence-based breast cancer mortality rates according to screening status were calculated for the five screening regions.

Results

Between 1990–1995, 15,541 patients were diagnosed with breast cancer. An analysis of ten-year follow-up after diagnosis resulted in 3903 breast cancer deaths, of which 2631 were not-invited and 345 were non-screened. Poisson regression analysis showed heterogeneity between the regions with a range of IBM ratios from 0.64 (95% CI: 0.46–0.90) to 1.08 (95% CI: 0.82–1.43).

Conclusions

Heterogeneity between the regions stresses the importance of a country- and/or region-specific estimate of self-selection. Adjusting for self-selection bias in the regional case-control studies would not change the breast cancer mortality reduction in three regions and would result in an even larger effect in two regions. Looking at the range of IBM ratios the overall influence of self-selection in the Netherlands is minor.

Trends in breast cancer mortality in Sweden before and after implementation of mammography screening

BACKGROUND

Incidence-based mortality modelling comparing the risk of breast cancer death in screened and unscreened women in nine Swedish counties has suggested a 39% risk reduction in women 40 to 69 years old after introduction of mammography screening in the 1980s and 1990s.

OBJECTIVE

We evaluated changes in breast cancer mortality in the same nine Swedish counties using a model approach based on official Swedish breast cancer mortality statistics, robust to effects of over-diagnosis and treatment changes. Using mortality data from the NordCan database from 1974 until 2003, we estimated the change in breast cancer mortality before and after introduction of mammography screening in at least the 13 years that followed screening start.

RESULTS

Breast mortality decreased by 16% (95% CI: 9 to 22%) in women 40 to 69, and by 11% (95% CI: 2 to 20%) in women 40 to 79 years of age.

DISCUSSION

Without individual data it is impossible to completely separate the effects of improved treatment and health service organisation from that of screening, which would bias our results in favour of screening. There will also be some contamination of post-screening mortality from breast cancer diagnosed prior to screening, beyond our attempts to adjust for delayed benefit. This would bias against screening. However, our estimates from publicly available data suggest considerably lower benefits than estimates based on comparison of screened versus non-screened women.

Breast cancer multifocality, disease extent, and survival

The prognostic information implied in subgross morphologic parameters such as lesion distribution (unifocal, multifocal, or diffuse) and disease extent in breast cancer has remained largely unexplored in the literature. We aimed to test whether these parameters influence survival in breast carcinoma. The parameters were assessed in a series of 574 cases, all documented in large-format histology sections. We used Cox proportional hazards regression accompanied by Kaplan-Meyer survival curves, with P < .05 regarded as significant. The invasive component was unifocal in 62% (311/499), multifocal in 24% (122/499), and diffuse in 5% (26/499) of the cases. Combining the in situ and invasive tumor components resulted in 48% (274/574) unifocal, 25% (141/574) multifocal, and 20% (117/574) diffuse tumors. Sixty percent (347/574) of the tumors were categorized as having limited extent (occupying an area <40 mm in largest dimension) and 29% (164/574) as extensive. Highly significant (P < .0001) differences were observed in 10-year disease-specific cumulative survival among the cases with unifocal, multifocal, and diffuse invasive (89.6%, 76.0%, and 63.6%, respectively) and combined (92.3%, 82.3%, and 75.7%, respectively) lesion distribution. Patients with extensive tumors exhibited a significantly lower cumulative survival (P < .0001) compared with those with limited extent (91.6% and 75.5%) and a statistically significantly 1.89-fold (95% confidence interval, 1.07-3.37; P = .03) risk for breast cancer death after controlling for tumor attributes, type of surgery, and adjuvant therapy. The hazard ratio for breast cancer death for mutifocal and/or diffuse tumors versus unifocal ones was 1.96 (95%; 1.11-3.48; P = .02) after controlling for the same factors. Lesion distribution and disease extent represent important independent survival-related prognostic parameters in breast carcinoma.

Breast cancer screening in the Czech Republic: time trends in performance indicators during the first seven years of the organised programme

Background

The Czech Breast Cancer Screening Programme (CBCSP) was initiated in September 2002 by establishing a network of accredited centres. The aim of this article is to describe progress in the programme quality over time after the inception of the organised programme.

Methods

The CBCSP is monitored using an information system consisting of three principal components: 1) the national cancer registry, 2) a screening registry collecting data on all screening examinations, further assessments and final diagnoses at accredited programme centres, and 3) administrative databases of healthcare payers. Key performance indicators from the European Guidelines have been adopted for continuous monitoring.

Results

Breast cancer incidence in the Czech Republic has steadily been increasing, however with a growing proportion of less advanced stages. The mortality rate has recently stabilised. The screening registry includes 2,083,285 records on screening episodes between 2002 and 2008. In 2007-2008, 51% of eligible women aged 45-69 were screened. In 2008, the detection rates were 6.1 and 3.7 per 1,000 women in initial and subsequent screening respectively. Corresponding recall rates are 3.9% and 2.2%, however, it is necessary to pay attention to further assessment performed during the screening visits. Benign to malignant open biopsy ratio was 0.1. Of invasive cases detected in screening, 35.6% was less than 10 mm in diameter. Values of early performance indicators, as measured by both crude and standardized estimates, are generally improving and fulfil desirable targets set by European Guidelines.

Conclusions

Mammography screening in the Czech Republic underwent successful transformation from opportunistic prevention to an organised programme. Values of early indicators confirm continuous improvement in different aspects of process quality. Further stimulation of participation through invitation system is necessary to exploit the full potential of screening mammography at the population level.

Introduction of organised mammography screening in Tyrol: results of a one-year pilot phase

BACKGROUND

Efficiency and efficacy of organised mammography screening programs have been proven in large randomised trials. But every local implementation of mammography screening has to check whether the well established quality standards are met. Therefore it was the aim of this study to analyse the most common quality indices after introducing organised mammography screening in Tyrol, Austria, in a smooth transition from the existing system of opportunistic screening.

METHODS

In June 2007, the system of opportunistic mammography screening in Tyrol was changed to an organised system by introducing a personal invitation system, a training program, a quality assurance program and by setting up a screening database. All procedures are noted in a written protocol. Most EU recommendations for organised mammography screening were followed, except double reading. All women living in Tyrol and covered by social insurance are now invited for a mammography, in age group 40-59 annually and in age group 60-69 biannually. Screening mammography is offered mainly by radiologists in private practice. We report on the results of the first year of piloting organised mammography screening in two counties in Tyrol.

RESULTS

56,432 women were invited. Estimated participation rate was 34.5% at one year of follow-up (and 55.5% at the second year of follow-up); 3.4% of screened women were recalled for further assessment or intermediate screening within six months. Per 1000 mammograms nine biopsies were performed and four breast cancer cases detected (N = 68). Of invasive breast cancer cases 34.4% were ≤ 10 mm in size and 65.6% were node-negative. In total, six interval cancer cases were detected during one year of follow-up; this is 19% of the background incidence rate.

CONCLUSIONS

In the Tyrolean breast cancer screening program, a smooth transition from a spontaneous to an organised mammography screening system was achieved in a short time and with minimal additional resources. One year after introduction of the screening program, most of the quality indicators recommended by the European guidelines had been reached.However, it will be necessary to introduce double reading, to change the rule for BI-RADS 3, and to concentrate on actions toward improving the participation rate.

Prognosis and pathology of screen-detected carcinomas: how different are they?

BACKGROUND

It has been observed that screen-detected breast cancers have a better prognosis than symptomatic tumors, even after taking pathological tumor attributes into account. This has led to the hypothesis that screen-detected tumors are substantially biologically different from symptomatic cancers.

METHODS

The pathology and survival by detection mode was investigated in 21,382 breast cancers diagnosed in women aged 50-64 years in the West Midlands, United Kingdom, between 1988 and 2004. Tumor attributes were compared using chi-square tests and logistic regression. Survival was analyzed using Cox regression.

RESULTS

Screen-detected cancers were significantly smaller, better differentiated, and less likely to be node-positive than symptomatic cancers (P < .001 in all cases). In addition, a higher proportion of screen-detected cancers were hormone receptor-positive, and a higher proportion were tubular carcinomas (P < .001). Survival was substantially better in screen-detected breast cancers (86% at 10 yearsvs 70% for interval cancers and 58% for cancers in women unexposed to screening). Adjustment for age, tumor size, nodal status, grade, histological type, and year of diagnosis accounted for 64% (interval cancers) and 68% (unexposed women) of these survival differences, respectively. Overall survival improved with time. Approximately half of this improvement was due to the increase over time in the proportion of tumors that were screen-detected.

CONCLUSION

The majority of the difference in prognosis between screen-detected and symptomatic breast cancers is due to the differences in routinely measured pathological features (size, type, grade, and nodal status), leaving a small residual difference to be accounted for by other biological differences.

Disparities in breast cancer mortality trends between 30 European countries: retrospective trend analysis of WHO mortality database

OBJECTIVE

To examine changes in temporal trends in breast cancer mortality in women living in 30 European countries.

DESIGN

Retrospective trend analysis. Data source WHO mortality database on causes of deaths Subjects reviewed Female deaths from breast cancer from 1989 to 2006

MAIN OUTCOME MEASURES

Changes in breast cancer mortality for all women and by age group (<50, 50-69, and >or=70 years) calculated from linear regressions of log transformed, age adjusted death rates. Joinpoint analysis was used to identify the year when trends in all age mortality began to change.

RESULTS

From 1989 to 2006, there was a median reduction in breast cancer mortality of 19%, ranging from a 45% reduction in Iceland to a 17% increase in Romania. Breast cancer mortality decreased by >or=20% in 15 countries, and the reduction tended to be greater in countries with higher mortality in 1987-9. England and Wales, Northern Ireland, and Scotland had the second, third, and fourth largest decreases of 35%, 29%, and 30%, respectively. In France, Finland, and Sweden, mortality decreased by 11%, 12%, and 16%, respectively. In central European countries mortality did not decline or even increased during the period. Downward mortality trends usually started between 1988 and 1996, and the persistent reduction from 1999 to 2006 indicates that these trends may continue. The median changes in the age groups were -37% (range -76% to -14%) in women aged <50, -21% (-40% to 14%) in 50-69 year olds, and -2% (-42% to 80%) in >or=70 year olds.

CONCLUSIONS

Changes in breast cancer mortality after 1988 varied widely between European countries, and the UK is among the countries with the largest reductions. Women aged <50 years showed the greatest reductions in mortality, also in countries where screening at that age is uncommon. The increasing mortality in some central European countries reflects avoidable mortality.

New diagnostic method for breast cancer based on clinical mammographic data and its clinical validation

BACKGROUND

Recently, the numbers of patients with breast cancer have increased rapidly in Japan, and about 40,000 people contract the disease annually today. Therefore, secondary prevention by breast cancer screening has become an important issue. Presently, mammography is used frequently for the diagnosis of breast cancer, but the reading of mammograms is difficult, and physicians must attend training classes specified by the Central Committee on Quality Control of Mammographic Screening and obtain a license to perform screening. Assessment categories are used for the evaluation of mammograms. Although they provide a scale for the diagnosis of breast cancer, the interpretation of mammograms is dependent on the physician's subjective judgment, and the advent of an objective evaluation method is awaited.

METHODS

We scored the size, shape, density, margin, border, and internal structure of mammographic images and evaluated the relationships of these scores with lesion categorization.

RESULTS

Since lesions could not be categorized by the analysis of any single item of mammographic images, the items were paired, and a new diagnostic system for breast cancer was prepared. When this system was applied, the diagnostic accuracy was very satisfactory, with a sensitivity of 100% (37/37) and a specificity of 92.9% (65/70) for category 5; 83.6% (51/61) and 97.8% (45/46), respectively, for category 4; and 88.9% (8/9) and 94.9% (93/98), respectively, for category 3.

CONCLUSION

In this study, findings concerning the margin and internal structure were important for the discrimination of category 5, and those concerning the size, shape, and density made major contributions to the discrimination of category 3.

Effectiveness of early detection on breast cancer mortality reduction in Catalonia (Spain)

Background

At present, it is complicated to use screening trials to determine the optimal age intervals and periodicities of breast cancer early detection. Mathematical models are an alternative that has been widely used. The aim of this study was to estimate the effect of different breast cancer early detection strategies in Catalonia (Spain), in terms of breast cancer mortality reduction (MR) and years of life gained (YLG), using the stochastic models developed by Lee and Zelen (LZ).

Methods

We used the LZ model to estimate the cumulative probability of death for a cohort exposed to different screening strategies after T years of follow-up. We also obtained the cumulative probability of death for a cohort with no screening. These probabilities were used to estimate the possible breast cancer MR and YLG by age, period and cohort of birth. The inputs of the model were: incidence of, mortality from and survival after breast cancer, mortality from other causes, distribution of breast cancer stages at diagnosis and sensitivity of mammography. The outputs were relative breast cancer MR and YLG.

Results

Relative breast cancer MR varied from 20% for biennial exams in the 50 to 69 age interval to 30% for annual exams in the 40 to 74 age interval. When strategies differ in periodicity but not in the age interval of exams, biennial screening achieved almost 80% of the annual screening MR. In contrast to MR, the effect on YLG of extending screening from 69 to 74 years of age was smaller than the effect of extending the screening from 50 to 45 or 40 years.

Conclusion

In this study we have obtained a measure of the effect of breast cancer screening in terms of mortality and years of life gained. The Lee and Zelen mathematical models have been very useful for assessing the impact of different modalities of early detection on MR and YLG in Catalonia (Spain).

Differences in Endpoints between the Swedish W-E (Two County) Trial of Mammographic Screening and the Swedish Overview: Methodological Consequences

Objectives

To characterize and quantify the differences in the number of cases and breast cancer deaths in the Swedish W-E Trial compared with the Swedish Overview Committee (OVC) summaries and to study methodological issues related to trials in secondary prevention.

Setting

The study population of the W-E Trial of mammography screening was included in the first (W and E county) and the second (E-county) OVC summary of all Swedish randomized mammography screening trials. The OVC and the W-E Trial used different criteria for case definition and causes of death determination.

Method

A Review Committee compared the original data files from Wand E county and the first and second OVC. The reason for a discrepancy was determined individually for all non-concordant cases or breast cancer deaths.

Results

Of the 2615 cases included by the W-E Trial or the OVC, there were 478 (18%) disagreements. Of the disagreements 82% were due to inclusion/exclusion criteria, and 18% to disagreement with respect to cause of death or vital status at ascertainment. For E-County, the OVC inclusion rules and register based determination of cause of death (second OVC) rather than individual case review (W-E Trial and 1st OVC) resulted in a reduction of the estimate of the effect of screening, but for W-County the difference between the original trial and the OVC was modest.

Conclusions

The conclusion that invitation to mammography screening reduces breast cancer mortality remains robust. Disagreements were mainly due to study design issues, while disagreements about cause of death were a minority. When secondary research does not adhere to the protocols of the primary research projects, the consequences of such design differences should be investigated and reported. Register linkage of trials can add follow-up information. The precision of trials with modest size is enhanced by individual monitoring of case status and outcome status such as determination of cause of death.

Do Asian breast cancer patients have poorer survival than their western counterparts? A comparison between Singapore and Stockholm

Introduction

The difference in breast cancer incidence and prognosis between ethnic groups seeks an explanation. We have recently shown that Swedish women are two to three times more likely to be diagnosed with breast cancer compared with Singaporean women. In the present paper, we compare breast cancer survival in the two countries.

Methods

We compared the survival of 10,287 Singaporean women and 17,090 Swedish women with breast cancer. Relative survival ratios were used to describe the prognosis in the two populations. A Poisson regression model was used to calculate relative risks for different follow-up periods, age groups, time of diagnosis and disease stages.

Results

The majority of the Swedish women had local cancer (80%) compared with Singaporean women (51%). The overall 5-year relative survival of the Swedish women appeared better (80%) than that of the Singaporean women (70%). A similar survival pattern was observed, however, between the two countries in a stage-by-stage comparison. Survival improved for all women in Singapore over the two decades, but only in the premenopausal women in Stockholm. In 1980 to 1989, premenopausal Singaporean women had 27% increased risk of death compared with Swedish women, adjusted for stage and year of follow-up, while the postmenopausal women had 48% increased risk. In 1990 to 1999, this risk decreased by 19% and 22% for the premenopausal and postmenopausal Singaporean women compared with the Swedish women.

Conclusions

The stage-dependent prognosis was similar for Singaporean women and for Swedish women. Singaporean women, both premenopausal and postmenopausal, had pronounced improvement in prognosis over the calendar periods, probably contributed by marked economic improvement, leading to better medical facilities and management with increased awareness of patients to diagnosis and treatment, as well as improved treatment options. Improvement seen only in the premenopausal women in Stockholm was probably due to improved treatment options.

Temporal trends in the use of adjuvant systemic therapy in breast cancer: a population based study in Sweden 1976-2005

BACKGROUND

Both adjuvant therapy and mammography screening can decrease breast cancer mortality and there is a need of knowing to what extent those two modalities are used in the population. Screening coverage is well documented but there is a scarcity of population-based data on use of systemic adjuvant treatment.

AIM

To describe the introduction, and trends in the use of adjuvant systemic therapy for breast cancer in two of six public health regions in Sweden.

MATERIAL & METHODS

Population-based data on use of adjuvant therapy were available from databases with documented high quality and high coverage data for Stockholm (1976-2005) and North Sweden (1980-2003, and 2005).

RESULTS

The use of systemic treatment was infrequent before the late 1980s in both regions, but increased during the 1990s. In 2005, the proportion of operable breast cancer patients treated with adjuvant endocrine therapy in the ages 40-59 was around 60 to 80%. The proportion adjuvant chemotherapy was less than 15% for the ages 70-74. For the north region the use of endocrine therapy increased successively over time, with an exception for age group 40-49 were a more rapidly increase occurred in the late 1990s. In Stockholm the increment was higher and more rapidly. There was no clear difference in chemotherapy use between the regions, and the use increased from the mid 1980s in age group 40-49, and in the early 1990s for women aged 50-59. In age group's 60-69 and 70-74 the use was relatively infrequent.

CONCLUSIONS

Trends in, and levels of the use of adjuvant systemic therapy for breast cancer varied over time in the two study regions, particularly for endocrine therapy. We consider that the differences between the regions mainly reflect different interpretations of new scientific evidence. We stress the importance of a good documentation of all new treatment protocols.

Breast cancer imaging: a perspective for the next decade

Breast imaging is largely indicated for detection, diagnosis, and clinical management of breast cancer and for evaluation of the integrity of breast implants. In this work, a prospective view of techniques for breast cancer detection and diagnosis is provided based on an assessment of current trends. The potential role of emerging techniques that are under various stages of research and development is also addressed. It appears that the primary imaging tool for breast cancer screening in the next decade will be high-resolution, high-contrast, anatomical x-ray imaging with or without depth information. MRI and ultrasonography will have an increasingly important adjunctive role for imaging high-risk patients and women with dense breasts. Pilot studies with dedicated breast CT have demonstrated high-resolution three-dimensional imaging capabilities, but several technological barriers must be overcome before clinical adoption. Radionuclide based imaging techniques and x-ray imaging with intravenously injected contrast offer substantial potential as a diagnostic tools and for evaluation of suspicious lesions. Developing optical and electromagnetic imaging techniques hold significant potential for physiologic information and they are likely to be of most value when integrated with or adjunctively used with techniques that provide anatomic information. Experimental studies with breast specimens suggest that phase-sensitive x-ray imaging techniques can provide edge enhancement and contrast improvement but more research is needed to evaluate their potential role in clinical breast imaging. From the technological perspective, in addition to improvements within each modality, there is likely to be a trend towards multi-modality systems that combine anatomic with physiologic information. We are also likely to transition from a standardized screening, where all women undergo the same imaging exam (mammography), to selection of a screening modality or modalities based an individual-risk or other classification.

Impacts of the Finnish service screening programme on breast cancer rates

BACKGROUND

The aim of the current study was to examine impacts of the Finnish breast cancer (BC) screening programme on the population-based incidence and mortality rates. The programme has been historically targeted to a rather narrow age band, mainly women of ages 50-59 years.

METHODS

The study was based on the information on breast cancer during 1971-2003 from the files of the Finnish Cancer Registry. Incidence, cause-specific mortality as well as incidence-based (refined) mortality from BC were analysed with Poisson regression. Age-specific incidence and routine cause-specific mortality were estimated for the most recent five-year period available; incidence-based mortality, respectively, for the whole steady state of the programme, 1992-2003.

RESULTS

There was excess BC incidence with actual screening ages; incidence in ages 50-69 was increased 8% (95 CI 2.9-13.4). There was an increasing temporal tendency in the incidence of localised BC; and, respectively, a decrease in that of non-localised BC. The latter was most consistent in age groups where screening had been on-going several years or eventually after the last screen. The refined mortality rate from BC diagnosed in ages 50-69 was decreased with -11.1% (95% CI -19.4, -2.1).

CONCLUSIONS

The current study demonstrates that BC screening in Finland is effective in reducing mortality rates from breast cancers, even though the impact on the population level is smaller than expected based on the results from randomised trials among women screened in age 50 to 69. This may be explained by the rather young age group targeted in our country. Consideration whether to targeted screening up to age 69 is warranted.

Organised mammography screening reduces breast cancer mortality: a cohort study from Finland

We evaluated the effectiveness and the efficacy of population-based mammography programme in Finland, and explored associations between the screening performance and the screening efficacy. The main outcome, incidence-based mortality from breast cancer, was estimated by invitation, participation, age at death, and screening centres categorised by recall rates. The study was based on an individual followup of screening invitees and participants from 1992 to 2003. The coverage of screening invitations was 95% among 50-59 years old women, and 20-40% among women aged 60-69 years. We compared observed deaths from breast cancer to expected breast cancer deaths without screening in ages 50-69 at death. The observed deaths were obtained from a cohort of individual invitees (n = 361,848). The expected deaths were defined by modelling breast cancer mortality from 1974 to 1985 and 1992 to 2003 at population level. The population data were derived from the same municipalities (n = 260) that were incorporated into the cohort. The breast cancer mortality among the invited women was reduced by 22% (relative risk 0.78, 95% confidence interval 0.70-0.87). After adjusting for the self-selection, the efficacy among the participants was 28% (0.72,0.56-0.88). No clear association between the recall rates and the screening efficacy was observed. The organised mammography screening in Finland is effective. The relationship between the estimates of process and outcome of mammography is not yet straightforward: effectiveness and efficacy remain the best estimates for evaluating the success of mammography screening.

Effect of mammographic service screening on stage at presentation of breast cancers in Sweden

BACKGROUND

Previous results have shown a reduction in mortality with service screening in Sweden on the order of 40%. If the rate of tumors at a later stage were similarly reduced, this would give further support to the mortality findings.

METHODS

The rates of lymph node-positive cancers, of tumors >2 cm in pathological size, and of tumors of TNM stage II or worse before and after the introduction of screening were compared in 13 areas in Sweden, adjusted for changes in overall incidence during the period of study and stratified by age (40-49 and 50-69 years).

RESULTS

Data were obtained on a total of 23,092 cancers and 10,177,113 person-years of observation. In women exposed to screening in the screening epoch, there was a significant 45% reduction in tumors of size >2 cm compared with the prescreening (relative risk [RR]=0.55, 95% confidence interval [CI]: 0.46-0.66) in the 40-49 age group, and a 33% reduction in the 50-69 group (RR=0.67, 95% CI: 0.62-0.72). For lymph node-positive and stage II+ disease, there were smaller but still significant reductions. No reduction in incidence in later-stage disease was observed in the unexposed women in the screening epoch.

CONCLUSIONS

Screening has significantly and substantially reduced the rates of larger tumors and lymph node-positive breast cancer in Sweden, and the magnitude of the reduction is consistent with the reduction in breast cancer mortality.

Quantitative diffusion-weighted MR imaging in the differential diagnosis of breast lesion

The role of diffusion-weighted magnetic resonance imaging (DWI) to differentiate breast lesions in vivo was evaluated. Sixty women (mean age, 53 years) with 81 breast lesions were enrolled. A coronal echo planar imaging (EPI) sequence sensitised to diffusion (b value=1,000 s/mm(2)) was added to standard MR. The mean diffusivity (MD) was calculated. Differences in MD among cysts, benign lesions and malignant lesions were evaluated, and the sensitivity and specificity of DWI to diagnose malignant and benign lesions were calculated. The diagnosis was 18 cysts, 21 benign and 42 malignant nodules. MD values (mean +/- SD x 10(-3) mm(2)/s) were (1.48 +/- 0.37) for benign lesions, (0.95 +/- 0.18) for malignant lesions and (2.25 +/- 0.26) for cysts. Different MD values characterized different malignant breast lesion types. A MD threshold value of 1.1 x 10(-3) mm(2)/s discriminated malignant breast lesions from benign lesions with a specificity of 81% and sensitivity of 80%. Choosing a cut-off of 1.31 x 10(-3) mm(2)/s (MD of malignant lesions -2 SD), the specificity would be 67% with a sensitivity of 100%. Thus, MD values, related to tumor cellularity, provide reliable information to differentiate malignant breast lesions from benign ones. Quantitative DWI is not time-consuming and can be easily inserted into standard clinical breast MR imaging protocols.

Reduced mortality for women with mammography-detected breast cancer in east Denmark and south Sweden

The 5-year relative survival from breast cancer in Denmark is 10 percentage points lower than in Sweden. This difference has been demonstrated previously as being caused partly by more involved lymph nodes and larger tumours in Denmark. Sweden has had nationwide mammography-screening coverage since 1991, whereas this is still in its infancy in Denmark. In the search for an explanation for the remaining survival difference, patient delay was a likely candidate. This study compared patient delay and mammography-detection between two national regions. Data on patient delay and mammography were obtained from hospital records from 1989 and 1994, and analysed using Cox proportional hazard analysis of death within the first 5 years, with the factors age, country, delay/mammography detection and established patho-anatomic variables. A comparison of patient delay and mammography detection in 1989 and 1994 showed more mammography-detected tumours in south Sweden and more women with long delay in east Denmark. Mammography detection, but not long patient delay, had a significant effect on the death hazard when adjusting for patho-anatomic risk factors. The hazard ratio was not eliminated in 1989, but in 1994, the hazard ratio between east Denmark and south Sweden was reduced from 1.3 to 1.1. In conclusion, patient delay did not appear to have any effect on 5-year survival when adjusting for patho-anatomic factors, but tumour detection by mammography affected survival favourably and partly explained the survival difference between east Denmark and south Sweden.

Reduction in breast cancer mortality from the organised service screening with mammography: 2. Validation with alternative analytic methods

BACKGROUND

In our companion article, incidence-based mortality analysis of data from breast cancer screening programs in 13 areas in Sweden indicated a 40% to 45% reduction in incidence-based breast cancer mortality among women actually screened. In this article, we apply new analytic methods for the evaluation of breast cancer mortality, using all breast cancer deaths in the period under study.

METHODS

Data were available from 13 areas on breast cancer mortality by year of diagnosis, year of death, and screening exposure. The period of study varied by area, the overall range of year of diagnosis being 1968 to 2001. We had data on 6,231 deaths and an average population of 555,676 women ages 40 to 69 years. Analysis of the effect of being screened was conducted using an alternative statistical analysis applied to all breast cancer deaths in the period of study, in addition to the incidence-based mortality analysis in our companion article. Data were analyzed using Poisson regression and adjusted for self-selection bias, contemporaneous changes in incidence, and changes in mortality independent of screening.

RESULTS

Using all deaths in the period of observation, a significant 42% reduction in breast cancer mortality was observed, adjusting for contemporaneous changes independent of screening [relative risk (RR), 0.58; 95% confidence interval (95% CI), 0.53-0.62]. After further adjustment for self-selection bias, the mortality reduction was 39% (RR, 0.61; 95% CI, 0.55-0.68), also highly significant.

CONCLUSIONS

These results indicate a reduction in breast cancer mortality of 39% in association with screening, after adjustment for contemporaneous changes and self-selection bias. These results confirm previous conclusions arrived at using incidence-based mortality analyses.

Reduction in Breast Cancer Mortality from Organized Service Screening with Mammography: 1. Further Confirmation with Extended Data

BACKGROUND

In an earlier publication, our evaluation of data from breast cancer screening programs in seven Swedish counties suggested a 40% reduction in incidence-based breast cancer mortality among women actually screened. In the current study, we expand the previous analysis from seven counties to 13 large areas within nine counties, including six of the original counties and seven additional areas, examine a longer period of follow-up (20-44 years), apply new analytic methods for the evaluation of incidence-based breast cancer mortality, and estimate the number needed to screen to save one life.

METHODS

Data from six of the original counties (one being excluded as it does not yet have 10 years of follow-up after the initiation of screening), with increased follow-up, and seven additional large areas, within three counties, representing approximately 45% of Swedish women, provide information about age at diagnosis, age at death, and screening history for 542,187 women in the prescreening and 566,423 women in the screening epochs. Regardless of year of diagnosis, there were a total of 6,231 deaths due to breast cancer in the period of study as a whole. Of these, 4,778 were incidence-based deaths in the two epochs, i.e., death among cases diagnosed within either the prescreening or screening period. Data were analyzed using Poisson regression and adjusted, when necessary, for self-selection bias, contemporaneous changes in incidence, and changes in mortality independent of screening.

RESULTS

Attendance was uniformly high, averaging 75% in the screening epochs. Recall rates for assessment varied from 4% to 5% at the first round of screening and approximately 3% at later rounds. Detection rates averaged five breast cancers per 1,000 women screened in the first round, and four breast cancers per 1,000 women screened in subsequent rounds. There was a significant 45% reduction in incidence-based breast cancer mortality among screened women in the screening epoch relative to incidence-based breast cancer mortality in the prescreening epoch (relative risk, 0.55; 95% confidence intervals, 0.51-0.59). After adjusting for self-selection bias, there still was a significant 43% reduction in incidence-based breast cancer mortality associated with screening (relative risk, 0.57; 95% confidence intervals, 0.53-0.62).

CONCLUSIONS

These results indicate a reduction in breast cancer mortality of between 40% and 45% in association with screening, after adjustment for self-selection bias. These results were obtained with modest human costs: the number needed to screen to save one life was estimated as 472.