Prevalence and clinical outcomes of young breast cancer (YBC) patients according to intrinsic breast cancer subtypes: Single institutional experience in Korea.

The purpose of our study was to investigate and identify comprehensively the clinicopathological features and long-term outcome of young breast cancer (YBC) according to intrinsic subtype. We analyzed clinical and pathological characteristics of 2844 women who were diagnosed with invasive breast cancer from 2000 to 2007 and the treatment outcomes by age at diagnosis. The median age of the patients was 46 years (range, 21-83 years), and we divided them into three age group: ≤35 years (Group 1), 36-50 years (Group 2), and >50 years (Group 3). During a median follow-up of 100 months, the 5-year recurrence-free survival rate (RFSR) and overall survival rate (OSR) were 90.8% and 94.6%, respectively. The 10-year estimated RFSR and OSR were 81.9% and 86.9%, respectively. The prognosis of TN subtype appeared not to be worse than that of other subtypes in Group 1. In Group 1 alone (≤35 years), subtype was not identified as an independent risk factor for distant recurrence-free survival (DRFS) in a Cox-regression multivariate model (hazard ratio, 0.85; 95% CI, 0.68-1.06; p = 0.148). This analysis revealed a very high prevalence of YBC in this cohort. The poor outcomes of YBC patients might result from an increased frequency of triple negative (TN)/HER2 subtypes and the more aggressive clinical behavior of ER-positive tumors compared with older patients. Further research to elucidate the biologic difference of the ER+ tumors of YBC patients is warranted.