Mammographic Breast Density as a Predictive Tool in Average-risk Women aged 40 to 59: a systematic review
Creators: name: Kernodle, Amber
Publisher: name: The University of North Carolina at Chapel Hill University Libraries
Year: 2014

description: Background: In 1976 Dr. John Wolfe introduced the relationship between breast tissue composition and breast cancer risk. Breast tissue composition is one of several well-established risk factors for breast cancer, but is not currently incorporated into commonly used risk prediction models or routinely used in clinical practice to recommend for or against routine screening. Knowledge of risk factors and their predictive abilities is important for creating appropriate screening strategies. It would be of value if breast tissue composition, alone or in combination with other risk factors, would allow for creating personalized screening plans for every woman based on her individual risk as screening can be harmful and costly. Objective: To assess whether the American College of Radiology (ACR) Breast Imaging-Reporting and Data System (BI-RADS) breast tissue composition categorization has a sufficient degree of incremental value beyond age to predict incidence and/or breast cancer-related mortality in average-risk women aged 40 to 59. Evaluation is based on the following criteria: magnitude of risk estimates, discriminatory ability, net reclassification index, clinical utility and cost-effectiveness. Search methods: I searched PubMed and EMBASE from January 1, 2003 to April 19, 2014. Radiologist assessment of breast tissue composition using mammography was the intervention of interest. I focused on outcomes assessed in the short-term, within 10 years of intervention. I excluded lifetime estimates. Exclusion criteria for the population included risk factors, such as personal history of breast cancer and BRCA 1 or BRCA 2 mutation carrier status. Main results: Eleven studies met the inclusion criteria. While exposure and outcome measurement were relatively consistent across studies, there was heterogeneity in study design, population age range, follow-up duration and outcomes assessed. Despite this, it is clear that there is a dose-response relationship between breast tissue composition and risk of in situ and invasive breast cancer. Across all of the studies, effect sizes were moderate. There was not a meaningful relationship with short-term mortality, though few studies in this review evaluated this outcome. The risk factor's ability to discriminate, separate cases from non-cases, was close to chance and not clinically proven to be superior to existing Breast Cancer Risk Assessment Tool (Gail Model). There were no studies that calculated the Net Reclassification Index (NRI), or evaluated clinical utility or cost-effectiveness. Limitations of the evidence: The BI-RADS lexicon used to describe breast tissue composition is subjective; creating measurement bias that can lead to inaccurate risk estimates. Outcome data (incidence and vital status) were obtained from population-based registries. Equal, valid and reliable measurement of the outcome rests on the completeness, validity and reporting timeliness of utilized databases. This information was variably reported and not easily obtainable. Lastly, breast density is not stable over time. Crossovers, movement from one category to another, can diminish risk estimates. Conclusion: Based on the available evidence, breast tissue composition, as currently assessed in routine clinical practice, does not fulfill the criteria to be valuable as a predictive tool. Authors of breast density notification laws should clarify intentions, critically examine the evidence and evaluate outcomes. Given subjectivity, focus could be shifted to objective measurements and other enterprising technologies, such as breast magnetic resonance imaging or 3D digital breast tomosynthesis.