LAUSR

Background: Breast cancer is no longer a single disease with high molecular heterogeneity. Gene profiling has identified at least 4 subtypes: Luminal A, Luminal B, HER2-enriched and basal-like breast cancer. Moreover, immunohistochemistry (IHC) classification is now considered a surrogate for establishing breast cancer subtypes. In previous report Luminal A was defined as ER and PgR positive, HER2 negative, Ki-67 low and recurrence risk low based on the multi-gene-expression assay. The distinction between Luminal A-like and Luminal B-like can be made by either using a high Ki-67 value (≥20%) or a low PgR value ( Methods: A total of 1866 invasive breast cancer patients from November 2001 to November 2016 were included in this study. The cases were classified as follows; LA as high PgR/low Ki-67 (850 cases), LB1 as high PgR/high Ki-67 (553 cases), LB2 as low PgR/high Ki-67 (226 cases), and LB3 as low PgR/low Ki-67 (237 cases). Out of all these cases, 1510 were treated with endocrine therapy alone. The median follow-up period was 78.1 months. Moreover, 23 of the cases underwent a 21-gene expression assay and the RS ( 26) was compared with our classification. Results: The median age was 57.4 years (range: 25 - 94). T1 tumors were more common in the LA group and rare in the LB2 group. Nuclear grade 3 and p53 overexpression were significantly correlated with LB2. Endocrine therapy alone was performed in 87.4% (LA), 77.4% (LB1), 58.8% (LB2) and 86.9% (LB3), retrospectively. There were significant differences in DFS between the LA group (5y DFS: 98%, 10 y DFS: 95.9%) and the LB2 group (5y: 89.9%, 10y: 83.6%; p 26. Conclusion: The patients with LA and LB3 (both: Ki-67 Citation Format: Arima N, Nishimura R, Osako T, Nishiyama Y, Okumura Y, Fujisue M, Toyozumi Y. Ki-67 index value and progesterone receptor status predict prognosis and suitable treatment in node-negative breast cancer patients with estrogen receptor positive and HER2 negative tumors [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P2-09-32.