Abstract PO4-25-09: HER2-Low and Ultra-Low expression in young women with luminal breast cancer in México

Abstract

Abstract Background and objective HER2-Low in breast cancer is a biomarker with new approaches for prognosis and medical treatment decisions. However, HER2-Ultra-Low is an area of novel research. Our objective was to describe the clinicopathologic characteristics and HER2 expression status of a group of Mexican young patients with luminal breast cancer. Methods One hundred and fifty-seven young patients (< 40 years) with luminal breast cancer diagnosed from 2014 to 2020 were included. Clinicopathologic features, hormone receptors, HER2 expression, and tumor infiltrating lymphocytes (TILs) were assessed. We categorized patients in three groups: HER2 negative (n=95, 60.5%), HER2-Low (n=33, 21.0%), and HER2-Ultra-Low (n=29, 18.5%). Descriptive statistics were used to report demographic, clinical and histopathological characteristics. Kaplan-Meier curves and log-rank or Mantel-Cox tests were used to determine survival. Statistical significance was established using a P value < 0.05. This analysis was performed using R (version 4.0.4) through R Studio interface (version 1.4.1106). Results The median of age at diagnosis was 36.1 years [range 32.8-38.8], with a median of follow-up of 5.08 years [range 3.58-6.52]. The most frequent histologic type was ductal infiltrating carcinoma (81%), and 49.4% presented grade two of differentiation. T2, N0 and clinical stage II were the most common (45.2%, 44.5, and 48.1%, respectively), and fourteen patients (9.0%) presented clinical stage IV. We found statistically significant differences in Ki67 and total TILs quantification between HER2 negative and HER2-Low. Progesterone receptor levels were higher for HER2 negative and Ultra-Low in comparison to HER2-Low. The total population had a 5-year overall survival of 84.9%. We found statistically significant differences in the median of survival between HER2 groups, with a shorter survival for HER2-Low. Conclusion To date, there are no studies that describe the clinical profile and OS of HER2-Low and Ultra-Low in young patients with luminal breast cancer in México. These preliminary findings could indicate the need for further investigation in prognosis, outcomes, and specific treatment in these patients. This study contributes to better understand the clinicopathologic profile of the HER2-Ultra-Low group and its differences with the HER2-Low group. Citation Format: Jesus Edgardo Hernandez Hernandez, César Octavio Lara Torres, Bryan Moreno Moran, Cynthia Villareal Garza, Fany Iris Porras Reyes, Víctor Manuel Pérez Sánchez, Alejandro Mohar. HER2-Low and Ultra-Low expression in young women with luminal breast cancer in México [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 PO4-25-09.