Abstract P5-08-18: Mortality rates associated with clinical and pathological characteristics of hormone receptor positive human epidermal growth factor receptor 2 negative early breast cancer: An analysis of the 2010-2016 surveillance, epidemiology, and end results data

Background: Breast cancer in the United States is diagnosed in over 90% of cases prior to evidence of distant metastasis (stages I–III) with approximately 70% of these cases classified as hormone receptor positive human epidermal growth factor receptor 2 negative (HR+HER2-).1 Despite primary surgery, radiation, and adjuvant endocrine/chemotherapy treatment options, approximately 20-30% of patients will experience relapse with distant metastases.2 Some clinical and pathological characteristics are known to be prognostic factors, but there are no standard definitions associated with level of risk. The objective of this study was to determine the extent of mortality associated with clinical and pathological characteristics of early breast cancer (EBC) using real-world data. Methods: Eligible patients from 2010–2016 Surveillance, Epidemiology, and End Results (SEER) data were aged ≥18 years and had a diagnosis of stage I, II, or III breast cancer with no distant metastases. Patients with HR-HER2- breast cancer were excluded. Mortality rates (95% confidence interval) by HER2 status and, for HR+HER2- tumors, by cancer stage, Bloom-Richardson (BR) grade, ipsilateral auxiliary lymph nodes status, and tumor size were estimated using Kaplan-Meier methods. Results: A total of 257,278 breast cancer patients were included: 214,578 HR+HER2-, 30,122 HR+HER2+, and 12,578 HR-HER2+. Mean age was 61.5 years, 99.1% were female, and 70.1% were white/non-Hispanic. The 5-year mortality rates were similar for HR+HER2- (12.3%) and HR+HER2+ (12.2%), whereas HR-HER2+ was numerically higher (16.8%). Within the HR+HER2- group, the 5-year mortality rates for subgroups are shown in Table 1. The highest mortality rate for both the node positive and micrometastases subgroups was approximately 30% for those who had 1–3 ipsilateral auxiliary lymph nodes, BR grade 3, and tumor size ≥5 cm. Conclusions: Patients with HR+HER2- EBC had similar mortality rates to patients with HR+HER2+ EBC. In patients with HR+HER2- EBC, higher mortality rates were numerically associated with ≥4 positive lymph nodes, BR grade 3, and greater tumor size. The effect on mortality was compounded with combinations of these histopathologic characteristics. References: 1. Howlander N, et al. J Natl Cancer Inst 2014;106:dju055; 2. Cardoso F, et al. Breast 2018;39:131-8. Citation Format: Jacqueline Brown, Michael W Method, David R Nelson. Mortality rates associated with clinical and pathological characteristics of hormone receptor positive human epidermal growth factor receptor 2 negative early breast cancer: An analysis of the 2010-2016 surveillance, epidemiology, and end results data [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P5-08-18.