Harms of Breast Cancer Screening: Systematic Review to Update the 2009 U.S. Preventive Services Task Force Recommendation

In 2009, the U.S. Preventive Services Task Force (USPSTF) recommended biennial mammography screening for women aged 50 to 74 years (1) on the basis of evidence of benefits and harms (2, 3). The USPSTF concluded that screening decisions for women aged 40 to 49 years should be based on individual considerations and that evidence was insufficient to assess benefits and harms for those aged 75 years or older (1). Although there is general consensus that mammography screening is beneficial for many women, benefits must be weighed against potential harms to determine the net effect of screening on individual women. Determining the balance between benefits and harms is complicated by several important considerations that are unresolved, including defining and quantifying potential harms; the optimal ages at which to begin and end routine screening; the optimal screening intervals; appropriate use of various imaging modalities, including supplemental technologies; values and preferences of women in regards to screening; and how all of these considerations vary depending on a woman's risk for breast cancer. This systematic review updates evidence for the USPSTF on the harms of breast cancer screening, including false-positive mammography results, overdiagnosis, anxiety, pain during procedures, and radiation exposure, and how these adverse effects vary by age, risk factor, screening interval, and screening modality. Systematic reviews of the effectiveness of screening (4), performance characteristics of screening methods (5), and the accuracy of breast density determination and use of supplemental screening technologies (6) are provided in additional reports. Methods Scope, Key Questions, and Analytic Framework The USPSTF determined the scope and key questions for this review by using established methods (7, 8). A standard protocol was developed and publicly posted on the USPSTF Web site. A technical report further describes the methods and includes search strategies and additional information (4). Investigators created an analytic framework outlining the key questions, patient populations, interventions, and outcomes reviewed (Appendix Figure 1). Key questions include the harms of routine breast cancer screening and how they differ by age, risk factor, screening interval, and screening modality (mammography [film, digital, or tomosynthesis], magnetic resonance imaging [MRI], and ultrasonography). Harms include false-positive and false-negative mammography results, overdiagnosis, anxiety and other psychological responses, pain during procedures, and radiation exposure. Overdiagnosis refers to women receiving a diagnosis of ductal carcinoma in situ (DCIS) or invasive breast cancer when they have abnormal lesions that are unlikely to become clinically evident during their lifetime in the absence of screening. Overdiagnosed women may be harmed by unnecessary procedures and treatments as well as by the burden of receiving a cancer diagnosis. Appendix Figure 1. Analytic framework and key questions. KQ = key question. * Excludes women with preexisting breast cancer; clinically significant BRCA1 or BRCA2 mutations, Li-Fraumeni syndrome, Cowden syndrome, hereditary diffuse gastric cancer, or other familial breast cancer syndrome; high-risk lesions (ductal carcinoma in situ, lobular carcinoma in situ, atypical ductal hyperplasia, or atypical lobular hyperplasia); or previous large doses of chest radiation (20 Gy) before age 30 y. False-positive and false-negative mammography results, biopsy recommendations due to false-positive mammography results, overdiagnosis and resulting overtreatment, anxiety, pain, and radiation exposure. Family history; breast density; race/ethnicity; menopausal status; current use of menopausal hormone therapy or oral contraceptives; prior benign breast biopsy; and, for women aged >50 y, body mass index. Mammography (film, digital, or tomosynthesis), magnetic resonance imaging, ultrasonography, and clinical breast examination (alone or in combination). The target population for the USPSTF recommendation includes women aged 40 years or older and excludes women with known physical signs or symptoms of breast abnormalities and those at high risk for breast cancer whose surveillance and management are beyond the scope of the USPSTF recommendations for preventive services (preexisting breast cancer or high-risk breast lesions, hereditary genetic syndromes associated with breast cancer, and previous large doses of chest radiation before age 30 years). Risk factors considered in this review are common among women who are not at high risk for breast cancer (9) (described in Appendix Figure 1). Data Sources and Searches A research librarian conducted electronic searches of the Cochrane Central Register of Controlled Trials, the Cochrane Database of Systematic Reviews, and Ovid MEDLINE through December 2014 for relevant studies and systematic reviews. Searches were supplemented by references identified from additional sources, including reference lists and experts. Studies of harms included in the previous systematic review for the USPSTF (2, 3) were also included. Study Selection Two investigators independently evaluated each study to determine eligibility based on prespecified inclusion criteria. Discrepancies were resolved through consensus. We included recently published systematic reviews; randomized, controlled trials (RCTs); and observational studies of prespecified harms. When available, studies providing outcomes specific to age, risk factors, screening intervals, and screening modalities were preferred over studies providing general outcomes. Studies that were most clinically relevant to practice in the United States were selected; relevance was determined by practice setting, population, date of publication, and use of technologies and therapies in current practice. Studies meeting criteria for high quality and with designs ranked higher in the study designbased hierarchy of evidence were emphasized because they are less susceptible to bias (for example, RCTs were chosen over observational studies). Data Extraction and Quality Assessment Details of the study design, patient population, setting, screening method, interventions, analysis, follow-up, and results were abstracted by one investigator and confirmed by another. Two investigators independently applied criteria developed by the USPSTF (7, 8) to rate the quality of each RCT, cohort study, casecontrol study, and systematic review as good, fair, or poor; criteria to rate studies with other designs included in this review are not available. Discrepancies were resolved through consensus. Data Synthesis Studies meeting inclusion criteria were qualitatively synthesized. Most studies in this review had designs for which quality rating criteria are not available, which limited data synthesis. When possible, we assessed the aggregate internal validity (quality) of the body of evidence for each key question (good, fair, or poor) by using methods developed by the USPSTF based on the number, quality, and size of studies; consistency of results between studies; and directness of evidence (7, 8). Role of the Funding Source This research was funded by the Agency for Healthcare Research and Quality (AHRQ) under a contract to support the work of the USPSTF. The investigators worked with USPSTF members and AHRQ staff to develop and refine the scope, analytic frameworks, and key questions; resolve issues during the project; and finalize the report. The AHRQ had no role in study selection, quality assessment, synthesis, or development of conclusions. The AHRQ provided project oversight; reviewed the draft report; and distributed the draft for peer review, including to representatives of professional societies and federal agencies. The AHRQ performed a final review of the manuscript to ensure that the analysis met methodological standards. The investigators are solely responsible for the content and the decision to submit the manuscript for publication. Results Of the 12004 abstracts identified by searches and other sources, 59 studies met inclusion criteria for key questions in this report, including 10 systematic reviews of 134 studies and 49 additional studies (Appendix Figure 2). Appendix Figure 2. Summary of evidence search and selection. RCT = randomized, controlled trial. * Cochrane Central Register of Controlled Trials and Cochrane Database of Systematic Reviews. False-Positive Mammography Results Two new observational studies estimated the cumulative probability of false-positive results after 10 years of screening with film and digital mammography, based on data from the Breast Cancer Surveillance Consortium, a large population-based database in the United States (Appendix Table 1) (10, 11). When screening began at age 40 years, the cumulative probability of receiving at least 1 false-positive mammography result after 10 years was 61% (95% CI, 59% to 63%) with annual screening and 42% (CI, 41% to 43%) with biennial screening (10). Estimates were similar when screening began at age 50 years. The cumulative probability of receiving a biopsy recommendation due to a false-positive mammography result after 10 years of screening was 7% (CI, 6% to 8%) with annual screening versus 5% (CI, 4% to 5%) with biennial screening for women who initiated screening at age 40 years and 9% (CI, 7% to 12%) with annual screening versus 6% (CI, 6% to 7%) with biennial screening for those who began at age 50 years. Appendix Table 1. U.S. Studies of Cumulative False-Positive Mammography and Biopsy Results In a separate analysis, rates of false-positive mammography results were highest among women receiving annual mammography who had extremely dense breasts and either were aged 40 to 49 years (65.5%) or used combination hormone therapy (65.8%) (11). The highest rates of biopsy due to false-positive mammography results were related to similar characteristics and ranged from 12% to 1