Abstract PO5-06-05: DISCORDANCE BETWEEN HORMONE RECEPTORS AND HER2 STATUS IN BREAST CANCER PATIENTS RELAPSE

Abstract

Abstract Introduction: Breast cancer (BC) is a heterogeneous disease, and during its progression, the tumor phenotype can undergo changes that are often associated with a poor prognosis. In this study, we aim to compare the discordance in estrogen receptor (ER), progesterone receptor (PgR), human epidermal growth factor receptor 2 (HER-2), and Ki-67 expression between primary and recurrent/metastatic lesions. Methods: This study is a retrospective analysis of 132 non-advanced breast cancer patients who experienced confirmed recurrence/metastasis at the Instituto Nacional de Enfermedades Neoplasicas between 2011 and 2022. Descriptive analysis was conducted to assess the expressions of ER, PgR, HER-2, and Ki-67 in primary and metastatic breast cancer, as well as clinical variables. Normality tests, including Kolmogorov-Smirnov and Shapiro-Wilk, were performed. The paired samples Wilcoxon test was used to determine significant differences between primary and recurrent/metastatic tumors. Additionally, Spearman's rank correlation coefficient was employed to evaluate the relationships of expression discordance. Results: Fifty-nine percent of patients presented locoregional recurrence, while 41% presented visceral metastasis. In the primary tumor, ER and PR expression were found in 63.6% and 55.3% of cases, respectively. HER2 status was determined as 0 (36.3%), +1 (22%), +2 (14.4%), +3 (26.5%), and not determined (0.8%) by IHC. For the recurrent/metastatic tumor, ER and PR expression were found in 59% and 34% of cases, respectively. HER2 status was determined as 0 (27.3%), +1 (19.7%), +2 (25%), +3 (25%), and not determined (3%). The median Ki-67 levels were 37% in the primary tumor and 40% in the recurrent/metastatic tumor. Significant differences were found for ER (p=0.014), PR (p< 0.001), and HER2 (p=0.019), but not for Ki-67 percentage (p=0.139). The discordance rates of ER, PR, HER2, and Ki-67 expression were 27.9%, 47.7%, and 26.3%, respectively. Conclussions: Discordance in hormone receptor expression between primary and recurrent/metastatic tumors is a common phenomenon, with ER showing a discordance rate of 27.9% and PR showing a higher rate of 47.7%. HER2 status also displayed significant discordance, with a 26.3% rate of discordant expression between primary and recurrent/metastatic tumors. The findings from this study emphasize the dynamic nature of breast cancer and the importance of comprehensive evaluation of biomarker expression in both primary and recurrent/metastatic tumors, to choose the best treatment options. Citation Format: Katia Roque, Iris Otoya, Natalia Valdivieso, Zaida Morante, Hugo Fuentes, Silvia Neciosup, Henry Gómez, Jorge Cotito, Gonzalo Ziegler, Estefania Peña, Tatiana Vidaurre, Ramon Andrade de Mello, Carlos Castañeda. DISCORDANCE BETWEEN HORMONE RECEPTORS AND HER2 STATUS IN BREAST CANCER PATIENTS RELAPSE [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 PO5-06-05.