PURPOSE: A 70-gene prognostic signature has prognostic value in patients with 
node-negative breast cancer in Europe. This diagnostic test known as 
"MammaPrint™ (70-gene prognostic signature)" was recently validated and 
implementation was feasible. Therefore, we assessed the 70-gene prognostic 
signature in Korean patients with breast cancer. We compared the risk predicted 
by the 70-gene prognostic signature with commonly used clinicopathological 
guidelines among Korean patients with breast cancer. We also analyzed the 
70-gene prognostic signature and clinicopathological feature of the patients in 
comparison with a previous validation study.
METHODS: Forty-eight eligible patients with breast cancer (clinical T1-2N0M0) 
were selected from four hospitals in Korea. Fresh tumor samples were analyzed 
with a customized microarray for the 70-gene prognostic signature. Concordance 
between the risk predicted by the 70-gene prognostic signature and risk 
predicted by commonly used clinicopathological guidelines (St. Gallen 
guidelines, National Institutes of Health [NIH] guideline, and Adjuvant! Online) 
was evaluated.
RESULTS: Prognosis signatures were assessed in 36 patients. No significant 
differences were observed in the clinicopathological features of patients 
compared with previous studies. The 70-gene prognosis signature identified five 
(13.9%) patients with a low-risk prognosis signature and 31 (86.1%) patients 
with a high-risk prognosis signature. Clinical risk was concordant with the 
prognosis signature for 29 patients (80.6%) according to the St. Gallen 
guidelines; 30 patients (83.4%) according to the NIH guidelines; and 23 patients 
(63.8%) according to the Adjuvant! Online. Our results were different from 
previous validation studies in Europe with about a 40% low-risk prognosis and 
about a 60% high-risk prognosis. The high incidence in the high-risk group was 
consistent with data in Japan.
CONCLUSION: The results of 70-gene prognostic signature of Korean patients with 
breast cancer were somewhat different from those identified in Europe. This 
difference should be studied as whether there is a gene disparity between Asians 
and Europeans. Further large-scale studies with a follow-up evaluation are 
required to assess whether the use of the 70-gene prognostic signature can 
predict the prognosis of Korean patients with breast cancer.