Abstract P4-08-35: Young age at diagnosis is associated with worse prognosis in the luminal A breast cancer subtype. A retrospective institutional cohort study

Abstract

Abstract Background: Breast cancer (BCA) presents with distinct molecular subtypes, each associated with different patterns of relapse, drug sensitivity, and prognosis. Although age at diagnosis is a recognized independent prognostic risk factor, its relative importance among molecular subtypes is not well documented. The aim of this study was to evaluate the prognostic role of age at diagnosis among BCA patients of different immunohistochemical subtypes (LuminalA, LuminalB, Her2, Triple-negative). Methods: We conducted a retrospective study of women with invasive BCA undergoing surgery at the Johns Hopkins Hospital from January 2000 - December 2016, excluding patients presenting with stage IV breast cancer. Patients were stratified into three age groups: ≤ 40, 41-60, and > 60 years, and multivariable analysis was performed using Cox regression. To explore age-related differences in gene expression, we identified differentially expressed genes (DEG) between age groups among BCA subtypes in the TCGA dataset. Finally, we identified key driver genes within DEG using a weighted gene co-expression network analysis. Results: Our cohort included 3,524 patients with a median follow-up of 85.1 months. LuminalA breast cancer patients had significantly lower 5-year Disease Free Survival (DFS) and Distant Metastasis-Free Survival (DMFS) in the ≤ 40 year age group compared to the 40-60 year age group (HR=2.69, 95%CI: 1.72 - 4.23 and HR=2.95, 95%CI: 1.78 - 4.90, respectively), while the other molecular subtypes showed no significant association of DFS or DMFS with age. Age was a stronger predictor of 5- year DFS and 5-year DMFS than tumor grade or proliferative index (Ki67) in LuminalA BCA patients, but not other subtypes. Gene expression data were obtained from 1097 BCA TCGA patients, divided into two groups (≤40y, n=36; >40y, n=455). We identified 374 DEG between ≤40y and >40y LuminalA BCA subsets. The DEG were enriched in 7 pathways, and the WGCNA analysis identified two modules of co-expressed genes. No age group-specific DEG were identified in non-LuminalA subtypes. Conclusion: Age at diagnosis may be an important prognostic factor in LuminalA BCA and may improve risk stratification and personalized therapy. Prospective studies are needed to further evaluate the prognostic value of age in this subset of BCA patients. Citation Format: Liu Z, Sahli Z, Wang Y, Wolff AC, Cope L, Umbricht CB. Young age at diagnosis is associated with worse prognosis in the luminal A breast cancer subtype. A retrospective institutional cohort study [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P4-08-35.