OBJECTIVE: van't Veer and colleagues developed a 70-gene prognosis profile known 
as MammaPrint to identify breast cancer patients who were at low risk of 
developing metastases. We evaluated the prognostic value of the 70-gene 
MammaPrint profile in Japanese women with node-negative breast cancer.
METHODS: Frozen tumour samples from 102 eligible node-negative breast cancer 
patients aged 70 or younger were characterized with the MammaPrint array. The 
patients were treated with breast-conserving therapy or mastectomy with axillary 
lymph node dissection between December 1998 and August 2001. About 73 percent 
received adjuvant hormonal therapy and 28 percent received adjuvant 
chemotherapy. The gene expression profiles obtained by MammaPrint classified the 
patients as high- or low-genomic risk. The median follow-up was 7.1 years.
RESULTS: Among the 102 patients, 20 (20%) were classified as low-genomic risk 
and 82 (80%) were classified as high-genomic risk. The probability of distant 
metastasis-free survival at five years was 100% for the low-risk group and 94% 
for the high-risk group.
CONCLUSIONS: The 70-gene MammaPrint prognosis profile accurately identified 
Japanese breast cancer patients at low risk of developing recurrences. In fact, 
100% of the individuals in the low-risk category remained metastasis-free for 
the duration of the observation period.