Abstract PS3-07-25: Clinical Characteristics of Chinese Patients with Early Invasive Breast Cancer Tested with 70-gene signature: Comparison with the MINDACT Cohort

Abstract Background: The 70-gene signature (MammaPrint®) predicts distant metastasis risk in early invasive breast cancer, especially HR+/HER2- patients with 0-3 nodes. Despite guideline inclusion, its performance in Chinese populations needs validation. This study compares clinicopathological features between a Chinese cohort and MINDACT. Methods: Retrospective analysis of 1900 Chinese early breast cancer patients tested with MammaPrint®. Clinical risk (C-High [C-H] or C-Low [C-L]) used modified Adjuvant! Online. Genomic risk (MammaPrint®): High Risk (G-H) or Low Risk (G-L), subcategorized by quartile (Ultra-Low [G-UL], Low but Not Ultra-Low [G-LNUL], High but Not Ultra-High [G-H1], Ultra-High [G-H2]). Compared G-H vs G-L within Chinese cohort, and key characteristics (age, T-stage, grade, nodal status) across overall population and four risk groups (C-H/G-H, C-H/G-L, C-L/G-H, C-L/G-L) with MINDACT (n=6693). Categorical variables were analyzed using Fisher’s exact test, with statistical significance defined as a two-sided P < 0.05. Results: Within the Chinese Cohort (G-H vs. G-L): Of 1,900 patients, 1,120 (58.9%) were G-L and 780 (41.1%) were G-H (distribution: G-UL 11.0%, G-LNUL 48.0%, G-H1 38.0%, G-H2 3.0%). Significant differences (p < 0.001) included:T-stage: G-L: T1 60.4%, T2 38.0%; G-H: T1 51.0%, T2 46.7%,Grade: G-L: G1 16.9%, G2 79.2%, G3 3.9%; G-H: G1 7.3%, G2 71.3%, G3 21.4%,PR & Ki-67: PR+ ≤20%: 9.9% (G-L) vs. 20.4% (G-H); Ki67 ≤14%: 48.8% (G-L) vs. 16.9% (G-H); Ki67 >14%: 51.2% (G-L) vs. 83.1% (G-H). Chinese Cohort vs. MINDACT (Overall & Risk Groups):Overall, Chinese patients were younger (<50 years: 40.3% vs. 33.3%, p < 0.001), had higher T2 stage (41.6% vs. 27.2%, p < 0.001), higher Grade 2 frequency (75.9% vs. 49.1%, p < 0.001), and slightly higher node positivity (23.7% vs. 21.0%, p = 0.013). Group-specific differences (p < 0.001) included:C-H/G-L: Higher Grade 2 (86.8% vs. 64.2%), higher T2 (69.1% vs. 54.4%), lower T1 (27.2% vs. 41.8%)C-H/G-H: Higher T2 (67.7% vs. 46.7%), predominant Grade 2 (60.1% vs. 23.3%), lower Grade 3 (37.5% vs. 75.6%)C-L/G-H: Younger age (<50 years: 49.9% vs. 30.1%), minimal advanced disease (T3: 0%; G3: 2.5%)C-L/G-L: Younger age (<50 years: 45.9% vs. 29.1%); predominantly T1, Grade 2, node-negative tumorsClinical-genomic discordance (C-H/G-L) was 24.0% in China, consistent with MINDACT (23.0%); overall concordance was 57.1%. Conclusion: Significant differences exist between Chinese and MINDACT cohorts in age (younger), T-stage (higher T2), and grade (higher Grade 2), persisting across MammaPrint® risk subgroups. These findings underscore the necessity of validating the 70-gene signature’s predictive value for chemotherapy decisions using China-specific data. Survival analysis of this large cohort and prospective studies will further evaluate its risk stratification performance and clinical utility in Chinese early breast cancer patients. Citation Format: H. Liu, G. Liu, W. Zhou, N. Li, Y. Wang, H. Hu, Y. Sheng, D. Zhou, C. Wang, G. Liu. Clinical Characteristics of Chinese Patients with Early Invasive Breast Cancer Tested with 70-gene signature: Comparison with the MINDACT Cohort [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 PS3-07-25.