The 70-gene signature (MammaPrint™) has been developed on retrospective series 
of breast cancer patients to predict the risk of breast cancer distant 
metastases. The microarRAy-prognoSTics-in-breast-cancER (RASTER) study was the 
first study designed to prospectively evaluate the performance of the 70-gene 
signature, which result was available for 427 patients (cT1-3N0M0). Adjuvant 
systemic treatment decisions were based on the Dutch CBO 2004 guidelines, the 
70-gene signature and doctors' and patients' preferences. Five-year 
distant-recurrence-free-interval (DRFI) probabilities were compared between 
subgroups based on the 70-gene signature and Adjuvant! Online (AOL) (10-year 
survival probability <90% was defined as high-risk). Median follow-up was 61.6 
months. Fifteen percent (33/219) of the 70-gene signature low-risk patients 
received adjuvant chemotherapy (ACT) versus 81% (169/208) of the 70-gene 
signature high-risk patients. The 5-year DRFI probabilities for 70-gene 
signature low-risk (n = 219) and high-risk (n = 208) patients were 97.0% and 
91.7%. The 5-year DRFI probabilities for AOL low-risk (n = 132) and high-risk 
(n = 295) patients were 96.7% and 93.4%. For 70-gene signature low-risk-AOL 
high-risk patients (n = 124), of whom 76% (n = 94) had not received ACT, 5-year 
DRFI was 98.4%. In the AOL high-risk group, 32% (94/295) less patients would be 
eligible to receive ACT if the 70-gene signature was used. In this prospective 
community-based observational study, the 5-year DRFI probabilities confirmed the 
additional prognostic value of the 70-gene signature to clinicopathological risk 
estimations such as AOL. Omission of adjuvant chemotherapy as judged appropriate 
by doctors and patients and instigated by a low-risk 70-gene signature result, 
appeared not to compromise outcome.