Abstract PS2-04-26: A comparison of clinical features and treatment outcomes in breast cancer leptomeningeal metastasis between African American and Caucasian populations: a single institution experience

Abstract Title: A comparison of clinical features and treatment outcomes in breast cancer leptomeningeal metastasis between African American and Caucasian populations: a single institution experience Background: Leptomeningeal disease (LMD) is a rare but devastating complication of malignancies, affecting up to 5% of breast cancer patients. Survival is poor, typically 3-4 months, despite aggressive treatment. There is very limited literature regarding the clinical variables of breast cancer and LMD in African Americans (AAs) and how treatment outcomes differ from non-AAs. Due to the unique demographics of the patient population at the Henry Ford Health Cancer, including a high percentage of AAs, we sought to analyze these factors as compared with Caucasian patients. Methods: We retrospectively reviewed breast cancer patients diagnosed with LMD at Henry Ford Health from August 2014 to August 2024. LMD diagnosis followed the European Society of Medical Oncology (ESMO) criteria, and treatment responses were assessed using modified Response Assessment in Neuro-Oncology (RANO)-LM criteria. Results: Forty-one patients were identified (18 Caucasian, 17 AA, 6 others), with a similar median age at diagnosis in AAs and Caucasians (52 vs 51 years). AAs had an equal number of hormone receptor (HR)-positive and triple-negative tumors (35%), followed by HER2-positive (29%), which is in contrast to Caucasians who had more HER2-positive (44%), followed by HR-positive (39%), and triple-negative (17%). Although the most common histology was invasive ductal in both AAs (71%) and Caucasians (65%), invasive lobular was more commonly seen in Caucasians (35%) vs only 12% in AAs. More AA patients had stage I disease at diagnosis (41%) vs only 6% of Caucasians, whose majority had de novo stage IV disease (67% vs 24% in AAs). 77% of AAs (13/17) had parenchymal brain metastases in addition to LMD, compared to only 7 of 18 in Caucasians. A higher proportion of AAs had better performance status (ECOG 1) than Caucasians (44% vs 6%). Among AAs, 47% received systemic therapy after LMD diagnosis, and 41% had CNS radiation, which was similar to Caucasians, among whom 44% received radiation and 39% received systemic therapy. Twenty-nine percent of AAs received intrathecal (IT) therapy (median treatments: 5) compared to 39% of Caucasians (median treatments: 9). Methotrexate was the most common IT drug in both groups. Among evaluable patients, there was a trend towards improved overall response rates in AAs (44% vs 25% in Caucasians), with similar disease control rates (78% vs 75%). Event-free survival (EFS) and overall survival (OS) were similar in both AAs (mEFS: 2.2 months; mOS: 2.2 months) and Caucasians (mEFS: 1.7 months; mOS: 1.6 months). On univariate analysis, poor performance status (ECOG) predicted worse EFS and OS in AAs, but this difference was not seen in Caucasians. Other factors, including receptor subtypes, histology, grade, stage at diagnosis, time to onset of LMD, and metastatic burden, showed no significant impact on EFS and OS in both populations. Conclusion: Though these numbers are small, our experience identified clinical differences between the AA and Caucasian populations, particularly in receptor status, performance status, stage at diagnosis, histology, and presence of parenchymal metastases. Although AAs had numerically better response rates, survival outcomes were similar in both groups. The variables and outcomes we identified will require larger population-based studies to generalize the findings. Citation Format: B. Ghimire, L. Rogers, M. Girgis. A comparison of clinical features and treatment outcomes in breast cancer leptomeningeal metastasis between African American and Caucasian populations: a single institution experience abstract. In: Proceedings of the San Antonio Breast Cancer Symposium 2025; 2025 Dec 9-12; San Antonio, TX. Philadelphia (PA): AACR; Clin Cancer Res 2026;32(4 Suppl):Abstract nr PS2-04-26.