Unless otherwise stated, the statistics and statements in this publication refer to invasive (not in situ) female breast cancer. Estimated new breast cancer cases. The overall estimated number of new invasive breast cancer cases diagnosed in the US in 2019 was projected using a spatiotemporal model based on incidence data from 48 states and the District of Columbia for the years 2001- 2015 that met the North American Association of Central Cancer Registries’ (NAACCR) data inclusion standards.8 This method considers geographic variations in sociodemographic and lifestyle factors, medical settings, and cancer screening behaviors as predictors of incidence, and also accounts for expected delays in case reporting. The number of DCIS cases diagnosed in 2019 were estimated by 1) approximating the actual number of cases in the 10 most recent data years (2007-2016) by applying annual age-specific incidence rates (based on 48 states) to corresponding population estimates for the overall US; 2) calculating the average annual percent change (AAPC) in cases over this time period; and 3) using the AAPC to project the number of cases three years ahead. These estimates were also partially adjusted for expected reporting delays using invasive factors. The estimated number of DCIS invasive cases by age and overall were calculated as the proportions of cases in each age group in the NAACCR data during 2012-2016 applied to the overall 2019 DCIS and invasive estimates. Incidence rates. Incidence rates are defined as the number of people who are diagnosed with cancer divided by the number of people who are at risk for the disease in the population during a given time period. Incidence rates in this publication are presented per 100,000 people per year and are age adjusted to the 2000 US standard population. Breast cancer incidence rates for the US in the most recent time period (2012-2016) were calculated using data on cancer cases collected by NAACCR.8 When referenced as such, NAACCR incidence data were made Breast Cancer Facts & Figures 2019-2020 31 available on the NAACCR website (naaccr.org) and within the Cancer in North America publications.217, 218 Longterm (1975-2016) incidence trends are based on the National Cancer Institute’s Surveillance, Epidemiology, and End Results (SEER) 9 registries, which account for about 8% of the US population. Analyses of trends (2001- 2016) by race/ethnicity are based on NAACCR incidence data and were adjusted for reporting delay using delay factors for the SEER 21 registries. Breast cancer subtype distribtuion. Using the approach of Anderson et al,219 we imputed missing estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor 2 (HER2) status assuming that status was missing at random, conditional on year of diagnosis, age, race/ethnicity, and ER/PR/ HER2 status. Specifically, two-step imputation was performed to obtain imputed HR status based on the joint distribution of ER (positive, negative, and missing) and PR (positive, negative, and missing) status. Please see DeSantis et al37 for more information on this method. Estimated breast cancer deaths. The overall estimated number of breast cancer deaths in the US is calculated by fitting the number of breast cancer deaths for 2002-2016 to a statistical model that forecasts the number of deaths expected to occur in 2019. Data on the number of deaths are obtained from the National Center for Health Statistics (NCHS) at the Centers for Disease Control and Prevention (CDC). Age-specific estimates were calculated using the proportions of deaths that occurred in each age group during 2013-2017 applied to the overall 2019 estimate. Mortality rates. Similar to incidence rates, mortality rates (or death rates) are defined as the number of people who die from cancer divided by the number of people at risk in the population during a given time period. Death rates were calculated using data on cancer deaths compiled by NCHS and population data collected by the US Census Bureau. All death rates in this publication were age adjusted to the 2000 US standard population. Survival. Five-year survival statistics are based on cancer patients diagnosed during 2009-2015; 10-year survival rates are based on diagnoses during 2001-2015; and 15-year survival rates are based on diagnoses during 1998-2015. All patients were followed through 2016. When referenced as such, 5-year survival statistics were originally published in SEER Cancer Statistics Review, 1975-2016.20 Probability of breast cancer diagnosis or death. Probabilities of developing or dying from breast cancer were calculated using DevCan 6.7.7 (Probability of Developing Cancer Software), developed by the National Cancer Institute.220 These probabilities reflect the average experience of women in the US who were not previously diagnosed with breast cancer and do not take into account individual behaviors and risk factors (e.g., utilization of mammography screening and family history of breast cancer). Screening. State-level prevalence estimates of mammography are based on Behavioral Risk Factor Surveillance System (BRFSS) data.187 The BRFSS is an ongoing system of surveys conducted by the state health departments in cooperation with the CDC. Data from the CDC’s National Health Interview Survey were used to generate national