Abstract PS4-09-09: Distinct Immune and Metabolic profiles in Latin American breast cancer patients with obesity enrolled in FLEX

Abstract Background: Latin American (LA) women are more likely to be diagnosed with aggressive early-stage breast cancer (EBC) compared to Non-Hispanic White (NHW) women, yet population-specific tumor biology remains underexplored. Previously, we reported elevated immune gene expression in BluePrint® (BP) Luminal B tumors in LA patients (pts) with EBC and obesity compared to Black and NHW cohorts. Here, we present updated clinical comparisons between LA, NHW and Black pts with EBC and whole transcriptome analysis (WTA) between BP Luminal B and Basal BC in pts with obesity. Methods: Clinical and WT data were analyzed from 15,577 EBC pts self-identified as LA, Black, or NHW enrolled in FLEX (NCT03053193), a prospective observational study with MammaPrint® risk of recurrence and BP molecular subtyping assays, and WT profiles. ImPrint, 53-gene immune signature, results (+/-) were generated for pts with hormone receptor positive (HR+) EBC. Chi-square and t-tests were conducted on clinical groups using arsenal R package. For WT comparisons, 215 obese LA pts with BP Luminal B and 77 with BP Basal EBC were matched to corresponding NHW and Black pts by age, T and N status. Differentially expressed genes (DEGs) were evaluated using limma, and pathway enrichment was performed using gene set enrichment analysis with Hallmark gene sets. Significant results were reported with adjusted p < 0.05. Results: Compared to Black and NHW pts, LA pts were younger and more often premenopausal (Table). Both LA and Black pts had statistically significantly higher rates of obesity compared to NHW pts. Significantly higher rates of MP High Risk 2, BP Basal and ImPrint+ tumors were observed in LA and Black pts vs NHW. WT comparisons among the obese subpopulations revealed that metabolic pathways, including adipogenesis, angiogenesis, epithelial-mesenchymal transition, and oxidative phosphorylation were significantly downregulated in EBC in LA pts vs NHW and Black cohorts. Conversely, immune-related pathways such as allograft rejection and interferon gamma response were enriched among LA pts with Basal cancers compared to NHW and Black groups. These coordinated pathway alterations suggest unique metabolic and immune profiles in LA EBC subtypes with a median absolute fold change of 1.3 among DEGs. Conclusion: The data suggest that signals from metabolic pathway alterations from modest immune-related gene upregulation may contribute to more aggressive tumor behavior in obese LA pts with EBC. Clinical and transcriptomic analyses demonstrated differences in Luminal B and Basal EBC biology among self-identified LA pts compared to NHW and Black cohorts, consistent with prior research. With further research, these findings may offer treatment targets which may enhance outcomes and reflect the importance of including racially and ethnically diverse pts in clinical trials to characterize population-specific differences in EBC outcomes. Citation Format: M. Mazo Canola, A. Santillan, J. Alberty-Oller, E. Dias, V. Kaklamani, A. Elkhanany, K. Hoskins, M. Habibi, R. Hampton, J. L. Barone, N. M. Johnson, N. Gordon, N. Sookhan, T. Bah, P. John, E. Aponte, S. Diab, V. Klimberg, N. Stivers, C. Page, S. Uygun, W. Audeh, J. O'Shaughnessy. Distinct Immune and Metabolic profiles in Latin American breast cancer patients with obesity enrolled in FLEX [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 PS4-09-09.