Patient demographics and germline mutation patterns across breast cancer molecular subtypes in a tertiary academic medical center: A retrospective study (October 2023–October 2025).

Abstract

e13142 Background: Breast cancer is the most commonly diagnosed malignancy among women in the United States and continues to be a leading cause of cancer-related mortality. Despite advancements in screening and treatment, disparities in outcomes persist, particularly in underserved populations. The literature estimates that germline mutations account for 5-10% of breast cancer cases. Hereditary susceptibility involves pathogenic variants in multiple cancer-predisposing genes. Characterizing germline mutation patterns across different breast cancer subtypes can enhance genetic risk assessment, counseling, and personalized management. This study examines patient demographics and germline mutation patterns across breast cancer subtypes at a tertiary academic medical center from October 2023 to October 2025. Methods: We conducted a descriptive, retrospective study of women aged 18 years and older with breast cancer who underwent germline genetic testing at a tertiary academic medical center between October 2023 and October 2025. A total of 107 patients were included in the study. Data were extracted from electronic medical records to identify breast cancer subtypes, patient demographics, and germline testing results. Patients with incomplete genetic testing results or insufficient clinical data were excluded. Germline testing was performed using commercially available certified laboratories, primarily with multigene hereditary cancer panels. Results: The age at diagnosis ranged from 35 to 91 years, with a mean age of 57 years. In this study, African American patients represented the largest group, making up 43% of the sample, with the majority demonstrating negative germline testing results. Among those with positive results in this group, variants of uncertain significance (VUS) were most commonly found in the ATM gene. Hispanic patients represented the second largest group at 37%, showing a predominant positive test result for germline mutations, characterized mainly as VUS in BRCA2 and CHEK2. The ER+/PR+/HER2− breast cancer subtype was the most common, accounting for 51% of cases, and the dominant ethnic group in this subtype was Hispanic. Triple-negative breast cancer was the second most common subtype at 13%, which was observed more frequently among African American patients, the majority of whom did not have a germline mutation. Conclusions: Patients at our tertiary academic center face substantial socioeconomic barriers, including restricted access to genetic testing. This study provides insight into an underserved, multiethnic population that is often underrepresented in clinical trials. These findings highlight the ongoing challenges in interpreting germline results and underscore the necessity for improved access to genetic counseling and testing to support equitable, personalized care.