Abstract 2905: Clinical features in relation to age at diagnosis in luminal breast cancer patients: A hospital-based case series study in Beijing, China
Authors: Koka Hela , Guo Changyuan , Abubakar Mustapha , Sung Hyuna , Sung Hyuna , Zhuo Bin , Tang Eric , Deng Joseph , Hu Nan , Lu Ning , Yang Xiaohong R. 
Published: August 2019

Abstract
Background
Breast cancer (BC) is a heterogenous disease that can be classified into various molecular subtypes. Patients with younger age at diagnosis are less likely to develop luminal A cancers. However, a large proportion of early-onset luminal BCs are seen among Asian BC patients. While this may be explained by the increasing exposure to Westernized lifestyle, germline genetics, breast density, or immune factors may also give rise to a distinct age-related biology in Asian BC. We investigated several tumor characteristics in luminal BC patients with respect to age, among women in Beijing, China.
Methods
Subjects in this study were diagnosed with invasive breast cancer and treated at the Cancer Hospital, Chinese Academy of Medical Sciences, Beijing, between 2008-2016. 7,543 luminal cases (ER+ and/or PR+), were further defined as Luminal A: ER+, PR+, HER2-, low grade (1/2); Luminal B/high grade: ER+ and/or PR+, HER2-, high grade (3); Luminal B/HER2+: ER+ and/or PR+, HER2+. Patients were divided into four age groups: &lt;40 (12.1%), 40-50 (34.2%), 50-60 (32.2%), and 60+ (21.5%) years old. We investigated the associations between age and tumor markers (ER, PR, HER2, KI67, P53, CK5/6, and EGFR) and features (tumor size, lymph node involvement, and histologic grade) using unconditional logistic regression.
Results
The mean age at diagnosis among these cases was 51.5 years (SD=10.8). Compared to older women (60+), patients diagnosed &lt;40 years old were more likely to have lower ER percentage/intensity, to be positive for HER2, P53, and EGFR, to have higher KI67, and luminal B/HER2+ tumors (p-values=&lt;.0001). PR showed a different and interesting pattern among patients in age group 40-50, who had higher values of PR percentage/intensity compared to women 60+ years old. After mutually adjusting for the significant tumor features, the associations for ER [OR&lt;40 vs 60+=0.34 (0.21, 0.55), OR40-50 vs 60+=0.22 (0.15, 0.32), strong vs. weak staining] and PR [OR&lt;40 vs 60+=2.95 (2.00, 4.35), OR40-50 vs 60+=4.22 (3.13, 5.68), strong vs. weak staining], HER2 positivity [OR&lt;40 vs 60+=1.60 (1.15, 2.23)], KI67 [OR&lt;40 vs 60+=1.52 (1.04, 2.21), quartile 4 vs. 1], and lymph nodal involvement [OR&lt;40 vs 60+=1.87 (1.38, 2.51)] remained significant. While younger patients in general were more likely to have luminal B/HER2+ tumors, women in age group 40-50 were less likely to develop luminal B/high grade BC [OR40-50 vs 60+=0.78 (0.63, 0.97)] compared to women 60+ years old.
Conclusion
We observed the known associations between younger age at diagnosis and more aggressive tumor features. We also found that patients in the age 40-50 group showed interesting associations with PR and the luminal B/high grade subtype. We intend to replicate these results in other Asian datasets and to explore the age associations with etiologic factors.
Citation Format: Hela Koka, Changyuan Guo, Mustapha Abubakar, Hyuna Sung, Hyuna Sung, Bin Zhuo, Eric Tang, Joseph Deng, Nan Hu, Ning Lu, Xiaohong R. Yang. Clinical features in relation to age at diagnosis in luminal breast cancer patients: A hospital-based case series study in Beijing, China [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 2905.