Screening with mammography uses X-ray imaging to find breast cancer before a lump can be felt. The goal is to treat cancer earlier, when a cure is more likely. The review includes seven trials that involved 600,000 women in the age range 39 to 74 years who were randomly assigned to receive screening mammograms or not. The studies which provided the most reliable information showed that screening did not reduce breast cancer mortality. Studies that were potentially more biased (less carefully done) found that screening reduced breast cancer mortality. However, screening will result in some women getting a cancer diagnosis even though their cancer would not have led to death or sickness. Currently, it is not possible to tell which women these are, and they are therefore likely to have breasts or lumps removed and to receive radiotherapy unnecessarily. If we assume that screening reduces breast cancer mortality by 15% after 13 years of follow-up 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.
Women invited to screening should be fully informed of both the benefits and harms. To help ensure that the requirements for informed choice for women contemplating whether or not to attend a screening programme can be met, 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.

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Screening for breast cancer with mammography.

PURPOSE: To (a) determine the performance of screening mammography, ultrasonography (US), and physical examination (PE); (b) analyze the influence of age, hormonal status, and breast density; (c) compare the size and stage of tumors detected with each modality; and (d) determine which modality or combination of modalities optimize cancer detection. MATERIALS AND METHODS: A total of 11,130 asymptomatic women underwent 27,825 screening sessions, (mammography and subsequent PE). Women with dense breasts subsequently underwent screening US. Abnormalities were deemed positive if biopsy findings revealed malignancy and negative if findings from biopsy or all screening examinations were negative. RESULTS: In 221 women, 246 cancers were found. Sensitivity, specificity, negative and positive predictive values, and accuracy of mammography were 77.6%, 98.8%, 99.8%, 35.8%, and 98.6%, respectively; those of PE, 27.6%, 99.4%, 99.4%, 28.9%, and 98.8%, respectively; and those of US, 75.3%, 96.8%, 99.7%, 20.5%, and 96.6%,...

Comparison of the Performance of Screening Mammography, Physical Examination, and Breast US and Evaluation of Factors that Influence Them: An Analysis of 27,825 Patient Evaluations

WITH neither the time nor the resources available to prevent, detect, or treat every disorder in every patient, which preventive, diagnostic, or therapeutic interventions should take priority? When

An assessment of clinically useful measures of the consequences of treatment.

Importance Breast cancer is a leading cause of premature mortality among US women. Early detection has been shown to be associated with reduced breast cancer morbidity and mortality. Objective To update the American Cancer Society (ACS) 2003 breast cancer screening guideline for women at average risk for breast cancer. Process The ACS commissioned a systematic evidence review of the breast cancer screening literature to inform the update and a supplemental analysis of mammography registry data to address questions related to the screening interval. Formulation of recommendations was based on the quality of the evidence and judgment (incorporating values and preferences) about the balance of benefits and harms. Evidence Synthesis Screening mammography in women aged 40 to 69 years is associated with a reduction in breast cancer deaths across a range of study designs, and inferential evidence supports breast cancer screening for women 70 years and older who are in good health. Estimates of the cumulative lifetime risk of false-positive examination results are greater if screening begins at younger ages because of the greater number of mammograms, as well as the higher recall rate in younger women. The quality of the evidence for overdiagnosis is not sufficient to estimate a lifetime risk with confidence. Analysis examining the screening interval demonstrates more favorable tumor characteristics when premenopausal women are screened annually vs biennially. Evidence does not support routine clinical breast examination as a screening method for women at average risk. Recommendations The ACS recommends that women with an average risk of breast cancer should undergo regular screening mammography starting at age 45 years (strong recommendation). Women aged 45 to 54 years should be screened annually (qualified recommendation). Women 55 years and older should transition to biennial screening or have the opportunity to continue screening annually (qualified recommendation). Women should have the opportunity to begin annual screening between the ages of 40 and 44 years (qualified recommendation). Women should continue screening mammography as long as their overall health is good and they have a life expectancy of 10 years or longer (qualified recommendation). The ACS does not recommend clinical breast examination for breast cancer screening among average-risk women at any age (qualified recommendation). Conclusions and Relevance These updated ACS guidelines provide evidence-based recommendations for breast cancer screening for women at average risk of breast cancer. These recommendations should be considered by physicians and women in discussions about breast cancer screening.

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Breast Cancer Screening for Women at Average Risk: 2015 Guideline Update From the American Cancer Society

Study Selection: Eight randomized, controlled trials of mammography and 2 trials evaluating breast self-examination were included. One hundred fifty-four publications of the results of these trials, as well as selected articles about the test characteristics and harms associated with screening, were examined. Data Extraction: Predefined criteria were used to assess the quality of each study. Meta-analyses using a Bayesian randomeffects model were conducted to provide summary relative risk estimates and credible intervals (CrIs) for the effectiveness of screening with mammography in reducing death from breast cancer. Data Synthesis: For studies of fair quality or better, the summary relative risk was 0.84 (95% CrI, 0.77 to 0.91) and the number needed to screen to prevent one death from breast cancer after approximately 14 years of observation was 1224 (CrI, 665 to 2564). Among women younger than 50 years of age, the summary relative risk associated with mammography was 0.85 (CrI, 0.73 to 0.99) and the number needed to screen to prevent one death from breast cancer after 14 years of observation was 1792 (CrI, 764 to 10 540). For clinical breast examination and breast self-examination, evidence from randomized trials is inconclusive. Conclusions: In the randomized, controlled trials, mammography reduced breast cancer mortality rates among women 40 to 74 years of age. Greater absolute risk reduction was seen among older women. Because these results incorporate several rounds of screening, the actual number of mammograms needed to prevent one death from breast cancer is higher. In addition, each screening has associated risks and costs.

Breast Cancer Screening: A Summary of the Evidence for the U.S. Preventive Services Task Force

REDUCTION IN MORTALITY FROM BREAST CANCER AFTER MASS SCREENING WITH MAMMOGRAPHY: Randomised Trial from the Breast Cancer Screening Working Group of the Swedish National Board of Health and Welfare

Further results are presented from the Swedish two-county breast cancer screening trial. The reduction in the rate of advanced cancers and of breast cancer mortality in the group allocated to screening when compared to the control group has accelerated with a further year of follow-up. Mortality due to other causes and the rate of other cancers remains similar in the two groups. Attention has been focused on the rate at which cancers start re-emerging among women with negative mammograms. Among women over 50 years of age at entry to the study, relatively few interval cancers are seen in the first two years after a screening test; in the third year the rate rises to nearly 50% of the comparable rate in the control group. Among women aged 40-49 years at entry, by contrast, the rate of interval cancers even in the first post screening year is nearly 40% of that in the controls and in the second year nearly 70%. In older women in the group allocated to screening, much of the breast cancer mortality comes from the refusers and little from the interval cancers; in younger women the picture is reversed. The implications for screening policy, including the interscreening interval are discussed.

What is the optimum interval between mammographic screening examinations? An analysis based on the latest results of the Swedish two-county breast cancer screening trial.

Randomised Trial from the Breast Cancer Screening Working Group of the Swedish National Board of Health and Welfare

A population-based, randomized, controlled breast cancer screening trial with single-view mammography as the only means of primary detection has been under way in Kopparberg county, Sweden, since October 1977. The 7-year results of the study show (1) a significant change in the stage distribution of breast cancers in the cohort invited to undergo screening (ASP) as compared to the control group. (2) This change is seen as an initial decrease in the proportion of advanced (stage II and more advanced) cancers in the ASP as compared to the control population, followed in the second and third round of screening by a significant decrease in the absolute number of these advanced cancers in the ASP relative to the control group. (3) A thorough follow-up of both populations will answer whether these preliminary findings will result in decreased breast cancer mortality in the population invited to screening.

L. H. Holmberg

Papers

REDUCTION IN MORTALITY FROM BREAST CANCER AFTER MASS SCREENING WITH MAMMOGRAPHY: Randomised Trial from the Breast Cancer Screening Working Group of the Swedish National Board of Health and Welfare

What is the optimum interval between mammographic screening examinations? An analysis based on the latest results of the Swedish two-county breast cancer screening trial.

Randomised Trial from the Breast Cancer Screening Working Group of the Swedish National Board of Health and Welfare

Significant reduction in advanced breast cancer. Results of the first seven years of mammography screening in Kopparberg, Sweden.