A trial to study the effect on breast cancer mortality of annual mammographic screening in women starting at age 40. Trial Steering Group

Bahcesehir long-term population-based screening compared to National Breast Cancer Registry Data: effectiveness of screening in an emerging country

PURPOSE

We aimed to show the effects of long-term screening on clinical, pathologic, and survival outcomes in patients with screen-detected breast cancer and compare these findings with breast cancer patients registered in the National Breast Cancer Registry Data (NBCRD).

METHODS

Women aged 40-69 years, living in Bahcesehir county, Istanbul, Turkey, were screened every 2 years using bilateral mammography. The Bahcesehir National Breast Cancer Registry Data (BMSP) data were collected during a 10-year screening period (five rounds of screening). BMSP data were compared with the NBCRD regarding age, cancer stage, types of surgery, tumor size, lymph node status, molecular subtypes, and survival rates.

RESULTS

During the 10-year screening period, 8758 women were screened with 22621 mammograms. Breast cancer was detected in 130 patients; 51 (39.2%) were aged 40-49 years. The comparison of breast cancer patients in the two programs revealed that BMSP patients had earlier stages, higher breast-conserving surgery rates, smaller tumor size, more frequent negative axillary nodal status, lower histologic grade, and higher ductal carcinoma in situ rates than NBCRD patients (p = 0.001, for all).

CONCLUSION

These results indicate the feasibility of successful population-based screening in middle-income countries.

Benefits and harms of breast cancer mammography screening for women at average risk of breast cancer: A systematic review for the European Commission Initiative on Breast Cancer

OBJECTIVES

Mammography screening is generally accepted in women aged 50-69, but the balance between benefits and harms remains controversial in other age groups. This study systematically reviews these effects to inform the European Breast Cancer Guidelines.

METHODS

We searched PubMed, EMBASE and Cochrane Library for randomised clinical trials (RCTs) or systematic reviews of observational studies in the absence of RCTs comparing invitation to mammography screening to no invitation in women at average breast cancer (BC) risk. We extracted data for mortality, BC stage, mastectomy rate, chemotherapy provision, overdiagnosis and false-positive-related adverse effects. We performed a pooled analysis of relative risks, applying an inverse-variance random-effects model for three age groups (<50, 50-69 and 70-74). GRADE (Grading of Recommendations Assessment, Development and Evaluation) was used to assess the certainty of evidence.

RESULTS

We identified 10 RCTs including 616,641 women aged 38-75. Mammography reduced BC mortality in women aged 50-69 (relative risk (RR) 0.77, 95%CI (confidence interval) 0.66-0.90, high certainty) and 70-74 (RR 0.77, 95%CI 0.54-1.09, high certainty), with smaller reductions in under 50s (RR 0.88, 95%CI 0.76-1.02, moderate certainty). Mammography reduced stage IIA+ in women 50-69 (RR 0.80, 95%CI 0.64-1.00, very low certainty) but resulted in an overdiagnosis probability of 23% (95%CI 18-27%) and 17% (95%CI 15-20%) in under 50s and 50-69, respectively (moderate certainty). Mammography was associated with 2.9% increased risk of invasive procedures with benign outcomes (low certainty).

CONCLUSIONS

For women 50-69, high certainty evidence that mammography screening reduces BC mortality risk would support policymakers formulating strong recommendations. In other age groups, where the net balance of effects is less clear, conditional recommendations will be more likely, together with shared decision-making.

Comparing CISNET Breast Cancer Incidence and Mortality Predictions to Observed Clinical Trial Results of Mammography Screening from Ages 40 to 49

BACKGROUND

The UK Age trial compared annual mammography screening of women ages 40 to 49 years with no screening and found a statistically significant breast cancer mortality reduction at the 10-year follow-up but not at the 17-year follow-up. The objective of this study was to compare the observed Age trial results with the Cancer Intervention and Surveillance Modeling Network (CISNET) breast cancer model predicted results.

METHODS

Five established CISNET breast cancer models used data on population demographics, screening attendance, and mammography performance from the Age trial together with extant natural history parameters to project breast cancer incidence and mortality in the control and intervention arm of the trial.

RESULTS

The models closely reproduced the effect of annual screening from ages 40 to 49 years on breast cancer incidence. Restricted to breast cancer deaths originating from cancers diagnosed during the intervention phase, the models estimated an average 15% (range across models, 13% to 17%) breast cancer mortality reduction at the 10-year follow-up compared with 25% (95% CI, 3% to 42%) observed in the trial. At the 17-year follow-up, the models predicted 13% (range, 10% to 17%) reduction in breast cancer mortality compared with the non-significant 12% (95% CI, -4% to 26%) in the trial.

CONCLUSIONS

The models underestimated the effect of screening on breast cancer mortality at the 10-year follow-up. Overall, the models captured the observed long-term effect of screening from age 40 to 49 years on breast cancer incidence and mortality in the UK Age trial, suggesting that the model structures, input parameters, and assumptions about breast cancer natural history are reasonable for estimating the impact of screening on mortality in this age group.

Assessing within-woman changes in mammographic density: a comparison of fully versus semi-automated area-based approaches

BACKGROUND

Mammographic density (MD) varies throughout a woman's life. We compared the performance of a fully automated (ImageJ-based) method to the observer-dependent Cumulus approach in the assessment of within-woman changes in MD over time.

METHODS

MD was assessed in annual pre-diagnostic films (from age 40 to early 50s) from 313 breast cancer cases and 452 matched controls using Cumulus (left medio-lateral oblique (MLO) readings) and the ImageJ-based method (mean left-right MLO readings). Linear mixed models were used to compare within-woman changes in MD among controls. Associations between individual-specific MD trajectories and breast cancer were examined using conditional logistic regression.

RESULTS

The age-related trajectories predicted by Cumulus and the ImageJ-based method were similar for all MD measures, except that the ImageJ-based method yielded slightly higher (by 2.54%, 95% CI 2.07%, 3.00%) estimates for percent MD. For both methods, the yearly rate of change in percent MD was twice faster after menopause than before, and higher BMI was associated with lower mean percent MD, but not associated with rate of change. Both methods yielded similar associations of individual-specific MD trajectories with breast cancer risk.

CONCLUSIONS

The ImageJ-based method is a valid fully automated alternative to Cumulus for measuring within-woman changes in MD in digitized films. The Age Trial is registered as an International Standard Randomized Controlled Trial, number ISRCTN24647151.

Effect of mammographic screening from age 40 years on breast cancer mortality in the UK Age trial at 17 years' follow-up: a randomised controlled trial

BACKGROUND

Age-specific effects of mammographic screening, and the timing of such effects, are a matter of debate. The results of the UK Age trial, which compared the effect of invitation to annual mammographic screening from age 40 years with commencement of screening at age 50 years on breast cancer mortality, have been reported at 10 years of follow-up and showed no significant difference in mortality between the trial groups. Here, we report the results of the UK Age trial after 17 years of follow-up.

METHODS

Women aged 39-41 from 23 UK NHS Breast Screening Programme units years were randomly assigned by individual randomisation (1:2) to either an intervention group offered annual screening by mammography up to and including the calendar year of their 48th birthday or to a control group receiving usual medical care (invited for screening at age 50 years and every 3 years thereafter). Both groups were stratified by general practice. We compared breast cancer incidence and mortality by time since randomisation. Analyses included all women randomly assigned who could be traced with the National Health Service Central Register and who had not died or emigrated before entry. The primary outcome measures were mortality from breast cancer (defined as deaths with breast cancer coded as the underlying cause of death) and breast cancer incidence, including in-situ, invasive, and total incidence. Because there is an interest in the timing of the mortality effect, we analysed the results in different follow-up periods. This trial is registered, number ISRCTN24647151.

FINDINGS

Between Oct 14, 1990, and Sept 25, 1997, 160 921 participants were randomly assigned; 53 883 women in the intervention group and 106 953 assigned to usual medical care were included in this analysis. After a median follow-up of 17 years (IQR 16·8-18·8), the rate ratio (RR) for breast cancer mortality was 0·88 (95% CI 0·74-1·04) from tumours diagnosed during the intervention phase. A significant reduction in breast cancer mortality was noted in the intervention group compared with the control group in the first 10 years after diagnosis (RR 0·75, 0·58-0·97) but not thereafter (RR 1·02, 0·80-1·30) from tumours diagnosed during the intervention phase. The overall breast cancer incidence during 17 year follow-up was similar between the intervention group and the control group (RR 0·98, 0·93-1·04).

INTERPRETATION

Our results support an early reduction in mortality from breast cancer with annual mammography screening in women aged 40-49 years. Further data are needed to fully understand long-term effects. Cumulative incidence figures suggest at worst a small amount of overdiagnosis.

FUNDING

National Institute for Health Research Health Technology Assessment programme and the American Cancer Society. Past funding was received from the Medical Research Council, Cancer Research UK, the UK Department of Health, and the US National Cancer Institute.

Estimating breast cancer mortality reduction and overdiagnosis due to screening for different strategies in the United Kingdom

Background:

The benefits and harms of population-wide mammography screening have been long debated. This study evaluated the impact of screening frequency and age range on breast cancer mortality reduction and overdiagnosis.

Methods:

We developed a Markov simulation model for the evaluation of mammography screening in a cohort of British women born in 1935–40.

Results:

For triennial screening in women aged 47–73, breast cancer mortality reduction and overdiagnosis was 18.1% (95% confidence interval: 17.3%, 19.0%) and 5.6% (5.1%, 6.1%), of all breast cancer deaths and diagnoses, respectively, from age 40 to 85 years. For annual screening in the same age range, estimates for both outcomes increased considerably to 35.0% (34.2%, 35.7%) and 7.6% (7.1%, 8.1%), respectively. For the age extension of triennial screening from 50–70 to 47–73, we estimated 5 (3, 7) incremental breast cancer deaths avoided and 14 (9, 19) incremental cases overdiagnosed per 10 000 women invited for screening.

Conclusions:

Estimates of mortality reduction and overdiagnosis were highly dependent on screening frequency, age range, and uptake, which may explain differences between some previous estimates obtained from randomised trials and from service screening.

Comparison of fully and semi-automated area-based methods for measuring mammographic density and predicting breast cancer risk

BACKGROUND

Mammographic density is a strong risk factor for breast cancer but the lack of valid fully automated methods for quantifying it has precluded its use in clinical and screening settings. We compared the performance of a recently developed automated approach, based on the public domain ImageJ programme, to the well-established semi-automated Cumulus method.

METHODS

We undertook a case-control study within the intervention arm of the Age Trial, in which ∼54,000 British women were offered annual mammography at ages 40-49 years. A total of 299 breast cancer cases diagnosed during follow-up and 422 matched (on screening centre, date of birth and dates of screenings) controls were included. Medio-lateral oblique (MLO) images taken closest to age 41 and at least one year before the index case's diagnosis were digitised for each participant. Cumulus readings were performed in the left MLO and ImageJ-based readings in both left and right MLOs. Conditional logistic regression was used to examine density-breast cancer associations.

RESULTS

The association between density readings taken from one single MLO and breast cancer risk was weaker for the ImageJ-based method than for Cumulus (age-body mass index-adjusted odds ratio (OR) per one s.d. increase in percent density (95% CI): 1.52 (1.24-1.86) and 1.61 (1.33-1.94), respectively). The ImageJ-based density-cancer association strengthened when the mean of left-right MLO readings was used: OR=1.61 (1.31-1.98).

CONCLUSIONS

The mean of left-right MLO readings yielded by the ImageJ-based method was as strong a predictor of risk as Cumulus readings from a single MLO image. The ImageJ-based method, using the mean of two measurements, is a valid automated alternative to Cumulus for measuring density in analogue films.

Is there excess mortality in women screened with mammography: a meta-analysis of non-breast cancer mortality

Background

The objective of our meta-analysis and systematic review was to analyze non-breast cancer mortality in women screened with mammography versus non-screened women to determine whether there is excess mortality caused by screening.

Methods

We searched PubMed and the Web of Science up to 30 November 2010. We included randomized controlled trials with non-breast cancer mortality as the main endpoint. Two authors independently assessed trial quality and extracted data.

Results

There was no significant difference between groups at 13-year follow-up (odds ratio = 1.00 (95% CI 0.98 to 1.03) with average heterogeneity I² = 61%) regardless of the age and the methodological quality of the included studies. The meta-analysis did not reveal excess non-breast cancer mortality caused by screening. If screening does have an effect on excess mortality, it is possible to provide an estimate of its maximum value through the upper confidence interval in good-quality methodological studies: up to 3% in the screened women group (12 deaths per 100,000 women).

Conclusions

The all-cause death rate was not significantly reduced by screening when compared to the rate observed in unscreened women. However, mammography screening does not seem to induce excess mortality. These findings improve information given to patients. Finding more comprehensive data is now going to be difficult given the complexity of the studies. Individual modeling should be used because the studies fail to include all the aspects of a complex situation. The risk/benefit analysis of screening needs to be regularly and independently reassessed.

Effects of age, breast density and volume on breast cancer diagnosis: a retrospective comparison of sensitivity of mammography and ultrasonography in China's rural areas

PURPOSE

Mammography has been confirmed as the only effective mode to improve the prognosis of patients with breast cancer in Western developed countries, but might not be a good choice in other areas of the world. One of the major challenges in China is to determine an optimal imaging modality for breast cancer screening. This study was designed to clarify the sensitivity of ultrasonography compared with that of mammography in rural China.

METHODS

We retrospectively studied the sensitivity of mammography and ultrasonography based on 306 breast cancer patients detected by the program of "screening for cervical cancer and breast cancer" performed in Chinese rural areas between January 2009 and December 2011, and analyzed the effects of age, breast density and volume on the sensitivity.

RESULTS

Stratified analysis showed that the sensitivity of breast ultrasonography was significantly higher than that of mammography in premenopausal patients (81.4% vs. 61.1%, p=0.02), in women ≤ 55 years of age (82.2% vs. 63.4%, p<0.01), in the high breast density group (American College of Radiology [ACR] levels 3-4) (85.9% vs. 60.6%, p<0.01) and in the small breast volume group (≤ 400 ml) (87.1% vs. 66.7%, p<0.01). Age had a significant effect on sensitivity of mammography (breast density and volume-adjusted odds ratio, 6.39; 95% confidence interval, 2.8-14.4 in age group > 55 compared to age group ≤ 45), but not that of ultrasonography. Neither breast density nor volume had significant effect on sensitivity of mammography or ultrasonography.

CONCLUSIONS

Ultrasonography is more sensitive than mammography in detecting breast cancer in women under 55 year-old Chinese, especially in those with high-density and relatively small breasts.

Screening for breast cancer with mammography

BACKGROUND

A variety of estimates of the benefits and harms of mammographic screening for breast cancer have been published and national policies vary.

OBJECTIVES

To assess the effect of screening for breast cancer with mammography on mortality and morbidity.

SEARCH METHODS

We searched PubMed (22 November 2012) and the World Health Organization's International Clinical Trials Registry Platform (22 November 2012).

SELECTION CRITERIA

Randomised trials comparing mammographic screening with no mammographic screening.

DATA COLLECTION AND ANALYSIS

Two authors independently extracted data. Study authors were contacted for additional information.

MAIN RESULTS

Eight eligible trials were identified. We excluded a trial because the randomisation had failed to produce comparable groups.The eligible trials included 600,000 women in the analyses in the age range 39 to 74 years. Three trials with adequate randomisation did not show a statistically significant reduction in breast cancer mortality at 13 years (relative risk (RR) 0.90, 95% confidence interval (CI) 0.79 to 1.02); four trials with suboptimal randomisation showed a significant reduction in breast cancer mortality with an RR of 0.75 (95% CI 0.67 to 0.83). The RR for all seven trials combined was 0.81 (95% CI 0.74 to 0.87). We found that breast cancer mortality was an unreliable outcome that was biased in favour of screening, mainly because of differential misclassification of cause of death. The trials with adequate randomisation did not find an effect of screening on total cancer mortality, including breast cancer, after 10 years (RR 1.02, 95% CI 0.95 to 1.10) or on all-cause mortality after 13 years (RR 0.99, 95% CI 0.95 to 1.03).Total numbers of lumpectomies and mastectomies were significantly larger in the screened groups (RR 1.31, 95% CI 1.22 to 1.42), as were number of mastectomies (RR 1.20, 95% CI 1.08 to 1.32). The use of radiotherapy was similarly increased whereas there was no difference in the use of chemotherapy (data available in only two trials).

AUTHORS' CONCLUSIONS

If we assume that screening reduces breast cancer mortality by 15% and that overdiagnosis and overtreatment is at 30%, it means that for every 2000 women invited for screening throughout 10 years, one will avoid dying of breast cancer and 10 healthy women, who would not have been diagnosed if there had not been screening, will be treated unnecessarily. Furthermore, more than 200 women will experience important psychological distress including anxiety and uncertainty for years because of false positive findings. To help ensure that the women are fully informed before they decide whether or not to attend screening, we have written an evidence-based leaflet for lay people that is available in several languages on www.cochrane.dk. Because of substantial advances in treatment and greater breast cancer awareness since the trials were carried out, it is likely that the absolute effect of screening today is smaller than in the trials. Recent observational studies show more overdiagnosis than in the trials and very little or no reduction in the incidence of advanced cancers with screening.

Modelling the overdiagnosis of breast cancer due to mammography screening in women aged 40 to 49 in the United Kingdom

INTRODUCTION

Overdiagnosis of breast cancer due to mammography screening, defined as the diagnosis of screen-detected cancers that would not have presented clinically in a women's lifetime in the absence of screening, has emerged as a highly contentious issue, as harm caused may question the benefit of mammographic screening. Most studies included women over 50 years old and little information is available for younger women.

METHODS

We estimated the overdiagnosis of breast cancer due to screening in women aged 40 to 49 years using data from a randomised trial of annual mammographic screening starting at age 40 conducted in the UK. A six-state Markov model was constructed to estimate the sensitivity of mammography for invasive and in situ breast cancer and the screen-detectable mean sojourn time for non-progressive in situ, progressive in situ, and invasive breast cancer. Then, a 10-state simulation model of cancer progression, screening, and death, was developed to estimate overdiagnosis attributable to screening.

RESULTS

The sensitivity of mammography for invasive and in situ breast cancers was 90% (95% CI, 72 to 99) and 82% (43 to 99), respectively. The screen-detectable mean sojourn time of preclinical non-progressive and progressive in situ cancers was 1.3 (0.4 to 3.4) and 0.11 (0.05 to 0.19) years, respectively, and 0.8 years (0.6 to 1.2) for preclinical invasive breast cancer. The proportion of screen-detected in situ cancers that were non-progressive was 55% (25 to 77) for the first and 40% (22 to 60) for subsequent screens. In our main analysis, overdiagnosis was estimated as 0.7% of screen-detected cancers. A sensitivity analysis, covering a wide range of alternative scenarios, yielded a range of 0.5% to 2.9%.

CONCLUSION

Although a high proportion of screen-detected in situ cancers were non-progressive, a majority of these would have presented clinically in the absence of screening. The extent of overdiagnosis due to screening in women aged 40 to 49 was small. Results also suggest annual screening is most suitable for women aged 40 to 49 in the United Kingdom due to short cancer sojourn times.

Effectiveness of mammography screening in reducing breast cancer mortality in women aged 39-49 years: a meta-analysis

BACKGROUND

Mammography screening of women >50 years of age significantly reduces breast cancer mortality in randomized controlled trials (RCTs). We sought to evaluate the effectiveness of mammography screening in women aged 39-49 years in reducing breast cancer mortality and to discuss previously published meta-analyses.

METHODS

PubMed/MEDLINE, OVID, COCHRANE, and Educational Resources Information Center (ERIC) databases were searched, and extracted references were reviewed. Dissertation abstracts and clinical trials databases available online were assessed to identify unpublished works. All assessments were independently done by two reviewers. All trials included were RCTs, published in English, included data on women aged 39-49, and reported relative risk (RR)/odds ratio (OR) or frequency data.

RESULTS

Nine studies were identified: the Kopparberg, Ostergotland (The Two-County study), Health Insurance Plan (HIP), Canada, Stockholm, Gothenburg, Edinburgh, Age, and Malmo trials. The individual trials were quality assessed, and the data were extracted using predefined forms. Using the DerSimonian and Laird random effects model, the results from the seven RCTs with the highest quality score were combined, and a significant pooled RR estimate of 0.83 (95% confidence interval [CI] 0.72-0.97) was calculated. Post hoc sensitivity analyses excluding studies with randomization before 1980 caused a loss of statistical significance (RR 0.87, 95% CI: 0.56, 1.13).

CONCLUSIONS

Mammography screenings are effective and generate a 17% reduction in breast cancer mortality in women 39-49 years of age. The quality of the trials varies, and providers should inform women in this age group about the positive and negative aspects of mammography screenings.

Screening for breast cancer with mammography

BACKGROUND

A variety of estimates of the benefits and harms of mammographic screening for breast cancer have been published and national policies vary.

OBJECTIVES

To assess the effect of screening for breast cancer with mammography on mortality and morbidity.

SEARCH STRATEGY

We searched PubMed (November 2008).

SELECTION CRITERIA

Randomised trials comparing mammographic screening with no mammographic screening.

DATA COLLECTION AND ANALYSIS

Both authors independently extracted data. Study authors were contacted for additional information.

MAIN RESULTS

Eight eligible trials were identified. We excluded a biased trial and included 600,000 women in the analyses. Three trials with adequate randomisation did not show a significant reduction in breast cancer mortality at 13 years (relative risk (RR) 0.90, 95% confidence interval (CI) 0.79 to 1.02); four trials with suboptimal randomisation showed a significant reduction in breast cancer mortality with an RR of 0.75 (95% CI 0.67 to 0.83). The RR for all seven trials combined was 0.81 (95% CI 0.74 to 0.87). We found that breast cancer mortality was an unreliable outcome that was biased in favour of screening, mainly because of differential misclassification of cause of death. The trials with adequate randomisation did not find an effect of screening on cancer mortality, including breast cancer, after 10 years (RR 1.02, 95% CI 0.95 to 1.10) or on all-cause mortality after 13 years (RR 0.99, 95% CI 0.95 to 1.03).Numbers of lumpectomies and mastectomies were significantly larger in the screened groups (RR 1.31, 95% CI 1.22 to 1.42) for the two adequately randomised trials that measured this outcome; the use of radiotherapy was similarly increased.

AUTHORS' CONCLUSIONS

Screening is likely to reduce breast cancer mortality. As the effect was lowest in the adequately randomised trials, a reasonable estimate is a 15% reduction corresponding to an absolute risk reduction of 0.05%. Screening led to 30% overdiagnosis and overtreatment, or an absolute risk increase of 0.5%. This means that for every 2000 women invited for screening throughout 10 years, one will have her life prolonged and 10 healthy women, who would not have been diagnosed if there had not been screening, will be treated unnecessarily. Furthermore, more than 200 women will experience important psychological distress for many months because of false positive findings. It is thus not clear whether screening does more good than harm. To help ensure that the women are fully informed of both benefits and harms before they decide whether or not to attend screening, we have written an evidence-based leaflet for lay people that is available in several languages on www.cochrane.dk.

False-positive results in the randomized controlled trial of mammographic screening from age 40 ("Age" trial)

BACKGROUND

False-positive recall is a recognized disadvantage of mammographic breast screening, and the rate of such recalls may be higher in younger women, potentially limiting the value of screening below age 50.

METHODS

Attendance and screening outcome data for 53,884 women in the intervention arm of the U.K. Age trial were analyzed to report observed false-positive recall rates during 13 years of trial fieldwork. The Age trial was a randomized controlled trial of the effect of mammographic screening from age 40 on breast cancer mortality, conducted in 23 National Health Service screening centers between 1991 and 2004. Women randomized to the intervention arm were offered annual invitation to mammography from age 40 or 41 to age 48.

RESULTS

Overall, 7,893 women (14.6% of women the intervention arm and 18.1% of women attending at least one routine screen) experienced one or more false-positive screen during the trial. The rates of false-positive mammography at first and subsequent routine screens were 4.9% and 3.2%, respectively. The cumulative false-positive rate over seven screens was 20.5%. Eighty-nine percent of women who had a false-positive recall at their previous screen attended their next invitation to routine screening.

CONCLUSIONS

The rates of false-positive recall in the Age trial were comparable with the national screening program; however, the positive predictive value of referral was lower. Experiencing a false-positive screen did not seem to lessen the likelihood of re-attendance in the trial.

IMPACT

The question of greatly increased false-positive rates in this age group and of their compromising re-attendance is refuted by the findings of this study.

Randomized controlled trial of mammographic screening from age 40 ('Age' trial): patterns of screening attendance

BACKGROUND

The Age trial was a randomized controlled trial to study the effect on breast cancer mortality of invitation to annual mammography from age 40 to 41. Uptake of invitation to screening mammography in UK women aged below 50 is of interest, particularly in the light of the recent announcement that the national breast screening programme will begin inviting women from age 47.

METHODS

The trial took place in 23 National Health Service breast screening units in England, Wales and Scotland between 1991 and 2004. Data on invitation and attendance during 13 years of trial fieldwork were analysed. The participants were 53,884 women in the intervention arm of the Age trial who were randomized to receive annual invitation to mammography from age 40 or 41 up to age 48. The trial is registered as an International Standard Randomised Controlled Trial, number ISRCTN24647151.

RESULTS

Uptake of invitation to routine screening was 68% at first round and 69% at subsequent rounds. A total of 43,709 women in the intervention arm (81%) attended at least one routine screen and 23,262 (43%) attended at least seven screens; 31,392 women attended 75% or more of all routine invitations they were offered. Previous trial attendance was a predictor of subsequent uptake; attendance was inversely related to Townsend deprivation score.

CONCLUSION

Uptake in this trial was comparable with that in the UK screening programme for women aged over 50. There was an inverse relationship between deprivation level and the number of screens attended.

Design issues in cancer screening trials

Randomised controlled trials avoid many of the potential biases associated with the evaluation of cancer screening. Nevertheless there are many issues concerning the design of such trials that require careful consideration and that will influence interpretation of the results. This article discusses issues related to recruitment and randomisation, which will affect the extent to which the population studied, is representative of the eventual target population of a screening programme. It addresses sample size considerations, the use of appropriate outcome measures and the timing of the intervention. Finally, issues related to ensuring appropriate analyses are discussed.

Assessing the amount of unscheduled screening ("contamination") in the control arm of the UK "Age" Trial

The UK Age Trial of mammographic screening from age 40 has reported a nonsignificant 17% reduction in breast cancer mortality calculated on an "intention to treat" basis. High levels of ad hoc screening in the control arm could potentially have diluted the estimated effect.

OBJECTIVES

To estimate the level of unscheduled mammography in the control arm of the UK Age Trial.

METHODS

Data were obtained from questionnaires sent to a random sample of 3,706 women at five centers in the control arm of this trial. Questions included in the Office for National Statistics Omnibus Surveys about the timing of and reasons for any breast screening provided comparable data. The overall response rate was 58.8%.

RESULTS

Overall, 24.9% (95% confidence interval, 23.0-26.8) of Age Trial controls responding reported ever having had a mammogram, 18.2% reported a mammogram for symptomatic reasons, and 8.4% reported unscheduled mammography. Overall, 4.0% and 1.8% of women reported symptomatic and unscheduled mammography, respectively, within the previous 12 months. Results from the Omnibus surveys were similar, 14.2% of women reported previous mammography for symptomatic reasons or follow-up after breast cancer and 6.8% reported unscheduled mammography.

CONCLUSIONS

The level of contamination due to mammographic screening in the control arm of the Age Trial was low and will have had a minimal effect on the estimated reduction in mortality from breast cancer.

IMPACT

Estimating the extent of screening in the control arm in randomized trials of screening is important to inform interpretation of the results.

Screening for breast cancer with mammography

BACKGROUND

A variety of estimates of the benefits and harms of mammographic screening for breast cancer have been published and national policies vary.

OBJECTIVES

To assess the effect of screening for breast cancer with mammography on mortality and morbidity.

SEARCH STRATEGY

We searched PubMed (November 2008).

SELECTION CRITERIA

Randomised trials comparing mammographic screening with no mammographic screening.

DATA COLLECTION AND ANALYSIS

Both authors independently extracted data. Study authors were contacted for additional information.

MAIN RESULTS

Eight eligible trials were identified. We excluded a biased trial and included 600,000 women in the analyses. Three trials with adequate randomisation did not show a significant reduction in breast cancer mortality at 13 years (relative risk (RR) 0.90, 95% confidence interval (CI) 0.79 to 1.02); four trials with suboptimal randomisation showed a significant reduction in breast cancer mortality with an RR of 0.75 (95% CI 0.67 to 0.83). The RR for all seven trials combined was 0.81 (95% CI 0.74 to 0.87). We found that breast cancer mortality was an unreliable outcome that was biased in favour of screening, mainly because of differential misclassification of cause of death. The trials with adequate randomisation did not find an effect of screening on cancer mortality, including breast cancer, after 10 years (RR 1.02, 95% CI 0.95 to 1.10) or on all-cause mortality after 13 years (RR 0.99, 95% CI 0.95 to 1.03).Numbers of lumpectomies and mastectomies were significantly larger in the screened groups (RR 1.31, 95% CI 1.22 to 1.42) for the two adequately randomised trials that measured this outcome; the use of radiotherapy was similarly increased.

AUTHORS' CONCLUSIONS

Screening is likely to reduce breast cancer mortality. As the effect was lowest in the adequately randomised trials, a reasonable estimate is a 15% reduction corresponding to an absolute risk reduction of 0.05%. Screening led to 30% overdiagnosis and overtreatment, or an absolute risk increase of 0.5%. This means that for every 2000 women invited for screening throughout 10 years, one will have her life prolonged and 10 healthy women, who would not have been diagnosed if there had not been screening, will be treated unnecessarily. Furthermore, more than 200 women will experience important psychological distress for many months because of false positive findings. It is thus not clear whether screening does more good than harm. To help ensure that the women are fully informed of both benefits and harms before they decide whether or not to attend screening, we have written an evidence-based leaflet for lay people that is available in several languages on www.cochrane.dk.

The effect of mammographic screening and hormone replacement therapy use on breast cancer incidence in England and Wales

DESIGN

An extended age-period-cohort model was used to estimate the effect of mammographic screening and hormone replacement therapy on breast cancer incidence in England and Wales between 1971 and 2001.

RESULTS

Incidence of breast cancer increased noticeably in women attending screening for the first time compared with nonattenders [rate ratio (RR), 1.73; 95% confidence interval (95% CI), 1.67-1.80]. Incidence was also 18% to 35% higher in attenders relative to nonattenders in subsequent screening rounds. In the first 3 years after women left the screening program, rates of breast cancer were reduced (RR, 0.88; 95% CI, 0.86-0.90), but by 7 to 9 years after screening, the rates had returned to the expected level (RR, 0.97; 95% CI, 0.94-1.00). The estimated RR of hormone replacement therapy on breast cancer incidence was 1.55 (95% CI, 1.37-1.75). Screening is estimated to increase a woman's lifetime risk of being diagnosed with breast cancer from 7.8% to 8.6%.

CONCLUSIONS

It is estimated that in the absence of screening, rates of breast cancer incidence would have continued to increase. A study at the individual subject level would be beneficial to assess the level of overdiagnosis associated with breast cancer screening.

Breast cancer mortality after screening mammography in British Columbia women

Mammographic screening is a proven method for the early detection of breast cancer. The authors analyzed the impact of service mammographic screening on breast cancer mortality among British Columbia women who volunteered to be screened by the Screening Mammography Program of British Columbia. A cohort of women having at least one mammographic screen by Screening Mammography Program of British Columbia between the ages of 40 and 79 in the period 1988-2003 was identified. All cases and deaths from breast cancer occurring in British Columbia were identified from the British Columbia Cancer Registry and linked to the screening cohort. Expected deaths from breast cancer in the cohort were calculated using incidence and survival rates for British Columbia women not in the cohort. Adjustment was made for age and socioeconomic status of their area of residence at time of diagnosis. The breast cancer mortality ratio was calculated by dividing observed by expected breast cancer deaths. The mortality ratio (95% confidence interval) was 0.60 (0.55, 0.65) for all ages combined (p < 0.0001). The mortality ratio in women aged 40-49 at first screening was 0.61 (0.52, 0.71), similar to that in women over 50 (p = 0.90). Exclusion of mortality associated with breast cancers diagnosed after age 50 in women starting screening in their 40s increased the mortality ratio to 0.63 (0.52, 0.77), but it remained statistically significant. Correction for self-selection bias using estimates from the literature increased the mortality ratio for all ages to 0.76. Mammographic screening at all ages between 40 and 79 reduced subsequent mortality rates from breast cancer.

Effect of mammographic screening from age 40 years on breast cancer mortality at 10 years' follow-up: a randomised controlled trial

BACKGROUND

The efficacy 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 finding could be due in part to screening of women after age 50 years. The Age trial was designed to study the effect 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 significance (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 significant, 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 benefits.

Screening for breast cancer with mammography

BACKGROUND

A variety of estimates of the benefits and harms of mammographic screening for breast cancer have been published and national policies vary.

OBJECTIVES

To assess the effect of screening for breast cancer with mammography on mortality and morbidity.

SEARCH STRATEGY

We searched PubMed (June 2005).

SELECTION CRITERIA

Randomised trials comparing mammographic screening with no mammographic screening.

DATA COLLECTION AND ANALYSIS

Both authors independently extracted data. Study authors were contacted for additional information.

MAIN RESULTS

Seven completed and eligible trials involving half a million women were identified. We excluded a biased trial from analysis. Two trials with adequate randomisation did not show a significant reduction in breast cancer mortality, relative risk (RR) 0.93 (95% confidence interval 0.80 to 1.09) at 13 years; four trials with suboptimal randomisation showed a significant reduction in breast cancer mortality, RR 0.75 (0.67 to 0.83) (P = 0.02 for difference between the two estimates). RR for all six trials combined was 0.80 (0.73 to 0.88). The two trials with adequate randomisation did not find an effect of screening on cancer mortality, including breast cancer, RR 1.02 (0.95 to 1.10) after 10 years, or on all-cause mortality, RR 1.00 (0.96 to 1.04) after 13 years. We found that breast cancer mortality was an unreliable outcome that was biased in favour of screening, mainly because of differential misclassification of cause of death. Numbers of lumpectomies and mastectomies were significantly larger in the screened groups, RR 1.31 (1.22 to 1.42) for the two adequately randomised trials; the use of radiotherapy was similarly increased.

AUTHORS' CONCLUSIONS

Screening likely reduces breast cancer mortality. Based on all trials, the reduction is 20%, but as the effect is lower in the highest quality trials, a more reasonable estimate is a 15% relative risk reduction. Based on the risk level of women in these trials, the absolute risk reduction was 0.05%. Screening also leads to overdiagnosis and overtreatment, with an estimated 30% increase, or an absolute risk increase of 0.5%. This means that for every 2000 women invited for screening throughout 10 years, one will have her life prolonged. In addition, 10 healthy women, who would not have been diagnosed if there had not been screening, will be diagnosed as breast cancer patients and will be treated unnecessarily. It is thus not clear whether screening does more good than harm. Women invited to screening should be fully informed of both benefits and harms.

Screening younger women with a family history of breast cancer – does early detection improve outcome?

Women with a family history are often offered mammographic surveillance at an earlier age and with greater frequency than those in the National Breast Screening Programme. In this study, we compared the survival of 62 breast cancer patients diagnosed in the context of a family history clinic offering 12-18 monthly mammographic screening with that of 1108 patients of the same age range but having no exposure to screening. We subtracted the expected additional observation time due to lead time from the survival of the screen-detected cases. Survival was significantly better in the family history group with relative hazards of 0.19 (95% CI 0.07-0.52, P<0.001) for breast cancer death and 0.19 (95% CI 0.08-0.43, P<0.001) for disease-free survival. After correcting for lead-time, the relative hazards were 0.24 (95% CI 0.09-0.66, P=0.005) for breast cancer death and 0.25 (95% CI 0.11-0.57, P<0.001) for disease-free survival. These results strongly suggest that screening younger women with a family history of breast cancer leads to improved survival. More precise estimates of the benefit will accrue from further follow-up and other such studies.

Overdiagnosis and overtreatment of breast cancer: overdiagnosis in randomised controlled trials of breast cancer screening

Data from randomised controlled trials of mammographic screening can be used to determine the extent of any overdiagnosis, as soon as either a time equivalent to the lead-time has elapsed after the final screen, or the control arm has been offered screening. This paper reviews those randomised trials for which breast cancer incidence data are available. In recent trials in which the control group has not been offered screening, an excess incidence of breast cancer remains after many years of follow-up. In those trials in which the control arm has been offered screening, although there is a possible shift from invasive to in situ disease, there is no evidence of overdiagnosis as a result of incident screens.

Efficacy of Breast Cancer Screening in the Community According to Risk Level

BACKGROUND

The efficacy of breast cancer screening in the community may differ from that suggested by the results of randomized trials, and no data have been available on efficacy among women who have different levels of breast cancer risk.

METHODS

We conducted a matched case-control study among women enrolled in six health plans in Washington, Oregon, California, Massachusetts, and Minnesota. We examined the efficacy of screening by mammography and/or clinical breast examination among women in two age cohorts (40-49 years and 50-65 years) and in two breast cancer risk levels (average and increased risk). Women who died from breast cancer from January 1, 1983, through December 31, 1998, (N = 1351; case subjects) were matched to control subjects (N = 2501) on age and risk level. Increased risk was defined as a family history of breast cancer or a breast biopsy noted in the medical records before the index date (defined as date of first suspicion of breast abnormalities in case subjects, with the same date used for matched control subjects). Data on screening, risk status, and other variables were abstracted from medical records. Conditional logistic regression was used to examine the association between breast cancer mortality and receipt of screening. All statistical tests were two-sided.

RESULTS

There were small, non-statistically significant associations between breast cancer mortality and receipt of screening during the 3 years prior to the index date for both the younger women [odds ratio (OR) = 0.92; 95% confidence interval (CI) = 0.76 to 1.13] and the older women (OR = 0.87; 95% CI = 0.68 to 1.12). The association among women at increased risk (OR = 0.74; 95% CI = 0.50 to 1.03) was stronger than that among women at average risk (OR = 0.96; 95% CI = 0.80 to 1.14), but the difference was not statistically significant (P = .17).

CONCLUSIONS

In this community-based study, screening history was not associated with breast cancer mortality. However, potential limitations of this study argue for a cautious interpretation of these findings.

Should we use MRI to screen women at high-risk of breast cancer?

Women with a strong family history of breast cancer are at increased risk of developing the disease themselves. Mammographic surveillance is recommended in the over 40 age group but the evidence of benefit from this strategy is limited until the individual reaches age 50 years. There is increasing evidence from the trials of breast magnetic resonance imaging that women at high risk may benefit from this technique as sensitivity is not dependent on breast density. The Dutch and Canadian studies have reported the sensitivity of MRI to be 71% and 77% compared to mammography which was 40% and 36%, respectively, in asymptomatic high risk cohorts.

Randomised controlled trial of mammographic screening in women from age 40: results of screening in the first 10 years

Debate continues over the effectiveness of screening by mammography in women below age 50. We report here on results of screening in the first 10 years of a randomised trial to study the effect on breast cancer mortality of invitation to annual mammography from age 40 to 41 compared to first invitation to the 3-yearly UK national programme at age 50–52. The trial is taking place in 23 NHS breast screening centres. Between 1991 and 1997, 160 921 women were randomised in the ratio 1 : 2 to intervention and control arms. Screening is by two views at first screen and single view subsequently; data on screening up to and including round five are now complete. Uptake of invitation to screening is between 68 and 70% at all but the latest screening rounds. Rates of referral for assessment are 4.6% at first screen and 3.4% at subsequent screens. Invasive cancer detection rates are 0.09% at first screen, and similar at rescreens until the sixth and later screens. There is little evidence of regular mammography in the trial control arm. The setting of this trial within the NHS breast screening programme should ensure applicability of results to a national programme.

Randomised controlled trial of mammographic screening in women from age 40: predicted mortality based on surrogate outcome measures

A trial in the UK to study the effect on mortality from breast cancer of invitation for annual mammography from the age of 40–41, has randomised a total of 160 921 women in the ratio 1 : 2 to the intervention and control arms. All breast cancers diagnosed in the two arms have been identified, and the histology reviewed. This paper presents the results of an interim analysis using surrogate outcome measures to compare predicted breast cancer mortality in the two arms based on 1287 cases diagnosed to 31.12.1999. Due to earlier diagnosis, there is currently an 8% excess of invasive breast cancers in the intervention arm. The ratio of predicted deaths at 10 years in the intervention arm relative to the control arm, adjusted for this excess diagnosis, ranges from 0.89 (95% confidence interval (CI) 0.78–1.01) to 0.90 (95% CI 0.80–1.01). Screening from age 40 may result in a lower reduction in breast cancer mortality than that observed in other trials including women below age 50. This analysis based on surrogate outcome measures suggests that a reduction in breast cancer mortality may be observed in this trial. However, a number of assumptions have been necessary and firm conclusions must await the analysis of observed mortality from breast cancer.

Screening for breast cancer

CONTEXT

Breast cancer screening in community practices may be different from that in randomized controlled trials. New screening modalities are becoming available.

OBJECTIVES

To review breast cancer screening, especially in the community and to examine evidence about new screening modalities.

DATA SOURCES AND STUDY SELECTION

English-language articles of randomized controlled trials assessing effectiveness of breast cancer screening were reviewed, as well as meta-analyses, systematic reviews, studies of breast cancer screening in the community, and guidelines. Also, studies of newer screening modalities were assessed.

DATA SYNTHESIS

All major US medical organizations recommend screening mammography for women aged 40 years and older. Screening mammography reduces breast cancer mortality by about 20% to 35% in women aged 50 to 69 years and slightly less in women aged 40 to 49 years at 14 years of follow-up. Approximately 95% of women with abnormalities on screening mammograms do not have breast cancer with variability based on such factors as age of the woman and assessment category assigned by the radiologist. Studies comparing full-field digital mammography to screen film have not shown statistically significant differences in cancer detection while the impact on recall rates (percentage of screening mammograms considered to have positive results) was unclear. One study suggested that computer-aided detection increases cancer detection rates and recall rates while a second larger study did not find any significant differences. Screening clinical breast examination detects some cancers missed by mammography, but the sensitivity reported in the community is lower (28% to 36%) than in randomized trials (about 54%). Breast self-examination has not been shown to be effective in reducing breast cancer mortality, but it does increase the number of breast biopsies performed because of false-positives. Magnetic resonance imaging and ultrasound are being studied for screening women at high risk for breast cancer but are not recommended for screening the general population. Sensitivity of magnetic resonance imaging in high-risk women has been found to be much higher than that of mammography but specificity is generally lower. Effect of the magnetic resonance imaging on breast cancer mortality is not known. A balanced discussion of possible benefits and harms of screening should be undertaken with each woman.

CONCLUSIONS

In the community, mammography remains the main screening tool while the effectiveness of clinical breast examination and self-examination are less. New screening modalities are unlikely to replace mammography in the near future for screening the general population.

Influence of annual mammography from age 40 on breast cancer pathology

The objective of this study was to determine the influence of annual mammography on pathology features of breast cancers in an invited population. We conducted a randomized trial of 53,890 invited and 106,971 control United Kingdom women who were recruited only from those aged 40 years, with central review of cancer histology. We compare the invasive cancer distribution for the categories of size, histological type, grade, and node status in subgroups of the invited population with that of controls. Among 1287 cancers identified in the total population through the end of December 1999, there are major differences among prevalence, incidence, interval, and lapsed-attender and nonattender subgroups for the distribution of cancer numbers in categories of chosen qualitative histological features. These reflect the biases known to affect a population exposed to screening. Comparing cancers from the unbiased group of the invited population with controls shows significant differences in distributions for size, grade, and node status but not histological type. Multivariate logistic regression shows significant reduction (odds ratio, 0.73; P = 0.043) in node-positive status for the unbiased group. We conclude that annual mammography from age 40 years significantly reduces size and positive-node status of invasive cancers in the invited population. The potential for phenotypic drift of grade emphasizes the relevance of screen detection of all grades at sizes smaller than 10 mm.

Should women under 50 be screened for breast cancer?

Despite some controversy in recent years, the majority of experts agree on the evidence for effectiveness of breast screening by mammography for women aged 50 years and above, but for those under 50 years, the picture is much less clear. However, the issue remains of importance both to policy makers and to individual women; although the incidence of breast cancer is lower at younger ages, the life years lost due to cancers diagnosed below 50 years amount to a third of all those lost due to the disease.

Radiation doses in the UK trial of breast screening in women aged 40-48 years

Although data have been published on the radiation doses involved in screening women in the UK in the age range 50-64 years, data have not been published for the screening of younger women, when one might expect higher doses and a different risk benefit balance. Therefore, data on the radiation doses arising from screening younger women (age range 40-48 years) as part of the UK age trial have been collected and reviewed. Each of the screening centres participating in the trial was asked to submit measurements of doses for samples of approximately 50 or 100 women. The doses for 2296 women were received. The dose estimates were corrected to take account of variations in composition with age and breast thickness and in the spectra used. The average received dose was 2.5 mGy per oblique film and 2.0 mGy per craniocaudal film. Although these doses are about 7% higher than those calculated for the screening of older women, this was owing to differences in equipment rather than age of the women. Age itself was not found to be a significant factor affecting the dose to screened women aged over or under 50 years. An identifiable sub-group of women with larger breasts who were screened using higher dose systems received doses that were about 4.2 times the average, and should be considered in any risk benefit analysis. Where modern mammography systems with automatic beam quality selection and alternative target and filter materials had been introduced, there was a 15% reduction in average received dose and up to a 50% reduction in received dose for large breasts.

Implications of pathologist concordance for breast cancer assessments in mammography screening from age 40 years

Three pathologists reviewed slides and reports of cancers arising in both the study and control populations of the U.K. trial of annual mammography screening from age 40 years. A total of 875 cases were scored independently as noninvasive, microinvasive, or invasive cancer, with the last also evaluated for histology grade, type, and lymphatic vascular invasion. Of these, 870 (99.2%) were confirmed malignant, 1 case had cytology only, and 5 were judged by all reviewers as benign. Reviewer complete concordance for the three classes of malignancy was achieved in 826 (95%) and majority agreement in 31 (3.6%) of 870 with complete data. All three readers recorded grade in 736 cancers, giving a kappa statistic of 0.69, 0.52, and 0.66 for grades I, II, and III, respectively, and 0.61 overall. Agreement that the cancer was special type or not was obtained in 671 (89.0%) with complete concordance in the nature of the type in 504 and majority view in 167; another 58 (7.7%) were characterised as "part special" pattern, with type disagreement in 23 (3%). The kappa statistic for single type subcategories in those cancers was substantial, at 0.68 overall. This improved to 0.76 for the last 230 invasive cancers after the pathologists agreed more explicit criteria for type discrimination. There was almost perfect agreement between original and review diagnosis of breast malignancy for both noninvasive/microinvasive and invasive cancer (kappa 0.84 and 0.91, respectively), justifying confidence in the diagnosis of breast cancer by U.K. pathologists. The specialists agreed substantially on qualitative histology features of type and grade of cancers, and improved further for typing by defining criteria. These consensus data, along with invasive size and node status, are reliable for use as surrogate measures of outcome, and to enhance interpretation of effect, when the trial case population sources are disclosed.

Breast cancer screening sensitivity in the NHSBSP: recent results and implications

This paper reviews the lessons learnt from the UK National Health Service Breast Screening programme.