Abstract PO2-25-11: Incidence of Breast Cancer in Louisiana Compared to the United States
Authors: Daily Avery , Cupp Julie , Trosclair Krystle 
Published: May 2024

Abstract
Aside from skin cancer, breast cancer is the most common cancer in American women. More specifically, one in eight women will develop breast cancer during their lifetime. Breast cancer is classified into subtypes defined by immunohistochemistry (IHC) expression of estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor 2 (HER2). ER+/PR+/HER2- tumors are the most common form of breast cancer and are typically associated with risk factors including older age, nulliparity, obesity following menopause, alcohol and tobacco use, sedentary lifestyle, and hormone therapy. ER-/PR-/HER2+ tumors comprise approximately 15-20% of breast cancers and are caused by overexpression of the HER2 gene. These tumors have similar risk factors to ER+/PR+/HER2- tumors, except for age. Women with HER2+ breast cancer are likely to be younger compared to ER+PR+/HER2-. Tumors lacking hormone receptors are classified as ER-/PR-/HER2-, otherwise known as triple-negative breast cancer (TNBC). TNBC represents 10%-20% of breast cancers and carries a poorer prognosis, shorter survival, and unresponsiveness to hormone therapy compared to other forms of breast cancer. TNBC has been associated with African American race, socioeconomically deprived population, younger age at diagnosis (most frequently in women ages 40-50), more advanced disease stage, higher grade, high mitotic indices, family history of breast cancer and BRCA1 mutations.
The primary aim of this study is to compare incidence of ER+/PR+/HER2-, ER-/PR-/HER2+, and ER-/PR-/HER2- (TNBC) in Louisiana to the national population. The Louisiana Tumor Registry (LTR) was utilized to obtain state and national level data. The LTR is a participant of the National Cancer Institute’s Surveillance, Epidemiology and End Results Program, and the Centers for Disease Control and Prevention’s National Program of Cancer Registries. Our study evaluated women in Louisiana diagnosed with ER+/PR+/HER2-, ER-/PR-/HER2+, and ER-/PR-/HER2- from 2010-2019. The populations were subdivided by age at time of diagnosis. Data was subdivided into ages 0-49, and &gt;50. Rates were calculated per 100,00 and age-adjusted to the 2000 United States Standard Population (19 age groups - Census P25-1130). A p-value of &lt; 0.05 indicates a significantly different rate in Louisiana comparative to the United States (SEER).
Our results are as follows. Unexpectedly, Louisiana has a significantly lower rate of ER+/PR+/HER2- cancer in women ages 0-49 and ages &gt;50 compared to the United States. Based on epidemiological risk factors, Louisiana should have a much higher rate of ER+/PR+/HER2- comparative to the United States population. Louisiana has a significantly higher rate of ER-/PR-/HER2+ cancer in women ages &gt;50 and ER-/PR-/HER2- (TNBC) in women ages 0-49 and ages &gt;50 compared to the United States. These findings are discordant with traditional epidemiologic studies regarding breast cancer and require further investigation.
Breast Cancer Incidence Rates1 by Age from 2010-2019 in Louisiana and the United States
Table 1: Breast Cancer Incidence Rates in women ages 0-49 and ages &gt;50 from 2010-2019 in Louisiana Compared to the United States.
Citation Format: Avery Daily, Julie Cupp, Krystle Trosclair. Incidence of Breast Cancer in Louisiana Compared to the United States [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO2-25-11.