Trends and Disparities in Breast Cancer Incidence-Mortality Rates of Black-White Women in the U.S.:

Updated: Dec 1, 2021

Introduction: Female Breast cancer is the second leading cause of cancer-related deaths in the U.S. While the incidence rate is lower in Hispanic-Black, the mortality rate is higher compared to Non-Hispanic White. This study investigates the trends of incidence and mortality rate of breast cancer in the U.S.: 2000-2016. It further explores the racial disparities between these two races. Method: Data for four age groups (15-39yrs, 40-64yrs, 65-74yrs, 75+yrs) of Hispanic-Black and Non-Hispanic White women for breast cancer were extracted from SEER; age-adjusted rate (U.S. 2000 standard population). Primary trend analysis was done with PyCharm 2020.3.3. (line charts) and regression models to check any significant increase or decrease over the years were done with JoinPoint (APC, 95% CI, significant p-value: <0.05). Result: Incidence rate is higher in Non-Hispanic White women, whereas mortality rate is higher in Hispanic Black. The 40-64yrs age groups showed an increase in incidence rate for Hispanic Black women, whereas an decrease for White women. The least vulnerable group, 15-39yrs age showed an increase in incidence rate in Non-Hispanic White women. The mortality rate was declining overall for both races. Conclusion: Disparities in oncologic healthcare, insurance system and socio-economic factors are possibly responsible for the higher mortality in Black American women. Improvements in these factors may reduce racial differences.

Breast cancer affects more than 1 in 10 million women globally [1]. The global cancer report 2018 of the International Agency for Research on Cancer (IARC) states female breast cancer is 1 of the top 3 cancer types worldwide with an estimation of 2.1 million new cases in 2018 [2]. It is the most common human neoplasm, responsible for 27% of cancers in developed countries [3]. In the United States, breast cancer is the second leading cause of mortality [1]. According to the Center for Prevention and Disease (CDC), 245,299 new cases of female breast cancer with 41,487 death occurred in this region in 2016 [4]. The Breast Cancer organization statistics of U.S. estimation postulates, about 1 in 8 women (about 12%) in the U.S. will develop invasive breast cancer in their lifetime [5]. Conversely, 1 in 39 women will die from breast cancer in the U.S. [6]. Surveillance, Epidemiology and End Results (SEER) program estimates almost 268,600 new cases of breast cancer to be diagnosed in the U.S. in 2019 [7].

Breast cancer occurs when an abnormal growth of cells is observed in any components of the breast, although this occurs most commonly in the lobules [8]. Different studies have categorized breast cancer in different ways and the most common is to classify it into two: 1) Invasive breast cancer and 2) Non-invasive breast cancer (in-situ). Multiple studies showed that major a portion of breast cancer type consists of invasive type carcinoma [8]. Invasive Ductal Carcinoma (IDC) is the most frequent type of BC globally which consists of 50% - 75% of all female breast cancers [9]. For non-invasive BC, Ductal Carcinoma In-Situ (DCIS) is prominent. DCIS is basically a neoplastic proliferation of epithelial cells which is limited to the ducts or lobules [10].

Racial disparity is high in the U.S. which makes it as one of the major contributing factors in breast cancer mortality in this region. By 2019, roughly 14% of the country’s population was Black (includes Hispanic) [11]. The South has the biggest concentration of Black people in the United States. More than half of the population (56%) lives there, with 17 percent in the Midwest, 17 percent in the Northeast, and 10 percent in the West [11]. The incidence and mortality rate of female breast cancer differ considerably by race/ethnicity and Black and Non-Hispanic White (from now referred to as “White”) women have higher rates of incidence and mortality rate than other races [12]. Typically, Black women are diagnosed with breast cancer at a younger age compared to White women [13]. Even though the incidence rate is lower for African American women (126.7 vs 130.8), the mortality rate is significantly higher (28.4 vs 20.3) in them [14]. Overall, the mortality rate is 40% higher for Black women [14]. This high incidence rate in White women and high mortality rate in Black women in the United States is a result of multiple factors. Dietary fat intake is strongly related to BC outcomes. Black women are often diagnosed with advanced stage of breast cancer where they cannot get stage-specific treatment anymore. Different studies have demonstrated physical activity is associated with lowering the risk factor of BC [15]. Compared to other races, African Americans (part of the Hispanic Black) are more likely to be overweight, obese, and have higher BMI and waist-to-hip ratios as they take less part in physical exercise [15]. In addition to that, they usually receive less from the recommended screenings [16]. The underlying reason behind this disparity is multilayered and multifaceted. Studies suggest that this effect of race on the stage of cancer is related to numerous socioeconomic factors such as education, income, insurance status, etc [17] [18].

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