Prognostic significance of molecular subtype in T1N0M0 breast cancer: Korean experience

Gene expression profiling studies have identified several breast cancer subtypes associated with markedly different clinical outcomes. In general, patients with stage I breast cancer have excellent outcomes. We assessed the clinicopathological characteristics and outcomes of patients with T1N0M0 breast cancer according to molecular subtype.

Seven hundred and sixty-two T1N0M0 breast cancer patients undergoing curative surgery between January 1990 and December 2007 were analyzed. Subtypes were classified according to hormone receptor (HR) and human epidermal growth factor receptor-2 (HER2) status as follows: HR+/HER2-, HR+/HER2+, HR-/HER2- (triple-negative, TN), and HR-/HER2+.

The distribution of subtypes was HR+/HER2-, 56.6%; HR+/HER2+, 10.1%; TN, 20.1%; and HR-/HER2+, 13.3%. Marked differences were observed among subtypes in multifocality/multicentricity, histological grade, extensive intraductal components, p53 expression and the Ki-67 index. There were differences in recurrence-free survival and overall survival among patients with different molecular subtypes (log-rank p < 0.001 and 0.024, respectively). By multivariate analysis, lymphovascular invasion and classification of molecular subtype were independent predictors of recurrence (p = 0.003 and 0.043, respectively). The TN subtype showed significantly worse recurrence-free survival compared to the HR+/HER2- subtype (hazard ratio, 4.54; 95% confidence interval, 1.60-12.86; p = 0.004).

Patients with T1N0M0 breast cancer, a group with generally favorable clinical outcomes, had prognoses that were associated with the molecular subtype. The TN subtype was an independent predictor for recurrence in patients with T1N0M0 breast cancer.