Abstract P4-06-06: Prevalence and clinical outcomes of young breast cancer (YBC) patients according to intrinsic breast cancer subtypes: Single institutional experience in Korea
Authors: Park YH , Kil WH , Lee JE , Nam SJ , Ahn JS , Im Y-H 
Published: August 2014

Abstract
Background: Unlike western countries, median age of breast cancer is much younger and the proportion of young breast cancer (YBC) patients has been reported to be much higher in Korea. Considering YBC has usually worse clinical outcomes than older patients, long-term treatment complication, and higher prevalence premenopausal women, special consideration for more proper approach treating age merit. Although there are many conflicting results, there is still needs to define YBC, especially for each BC subtype. The purpose of our study was to investigate and determine clinicopathologic features and long-term outcome of YBC according to intrinsic subtype comprehensively.
Methods: We retrospectively analyzed the presenting clinical and pathologic characteristic with intrinsic subtype using surrogate IHC (immunohistochemical) staining and treatment outcomes of 2,844 women who diagnosed with invasive breast cancer with age from 2000 to 2007 in Samsung Medical Center. We divided into three age groups as follows: ≤35 years (group 1), 35-50 years (group 2), and &gt;50 years (group 3). In addition, intrinsic subtypes using IHC were divided into four groups as follows: Hormone receptor (HR)-+/HER2-; HER2+/HR-; HER2+/HR-; Triple Negative (TN).
Results: During median follow-up duration of 100 months, 5-year recurrence free survival rate (RFSR) and overall survival rate (OSR) of all 2,884 patients were 90.8% and 94.6%, respectively. 10-year estimated RFSR and OSR were 81.9% and 86.9%, respectively. Median age was 46 years (range 21-83). Breast cancer patients aged with 40 or less comprised of 22% of all population in our cohort. Distribution of HR+ subtypes was different among three age groups (53.0% for group 1 vs. 65.1% for group 2 vs. 58.9% for group 3, p&lt;0.0001). Higher prevalence of TN was found in group 1 (≤35) than in other age groups (23.7% for group 1 vs. 15.2% for group 2 vs. 16.6% for group 3, p&lt;0.0001). Group 1 showed worse long term clinical outcomes compared with other groups [distant recurrence rate (DRR) 21.3% for group 1 vs. 11.8% for group 2 vs. 12.6% for group 3, p&lt;0.0001]. Group 1 (≤35) showed the worst clinical outcomes among three age groups in terms of RFS, DRFS, and OS for patients with HR+ and HER2+ subtypes with statistical significances. However, there is no difference of clinical outcomes among three age groups in TN subtypes. Prognosis of TN subtype appeared not to be worse than other subtypes in group 1. Limiting to group 1(≤35), subtype was not identified as an independent risk factor for DRFS in Cox-regression multivariate model (hazard ratio 0.85, 95% CI 0.68-1.06, p = 0.148).
Conclusions: This analysis showed much high prevalence of YBC in this patients’ cohort. Poor outcomes of YBC patients might be from increased frequency of TN/HER2 subtypes and more aggressive clinical behavior of ER-positive tumors than in older patients. Clinical implications of age on tumor behavior were different according to subtypes. Further research to elucidate biologic difference of ER+ tumor in YBC patients is warranted.
Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P4-06-06.