PURPOSE: Most node-negative breast cancer patients are older and postmenopausal 
and are increasingly being offered adjuvant chemotherapy despite their low 
overall risk of distant relapse. A molecular diagnostic test with high negative 
predictive value (NPV) for distant metastasis in this subgroup would spare many 
older breast cancer patients adjuvant treatment.
EXPERIMENTAL DESIGN: We determined the NPV and positive predictive value of the 
MammaPrint assay in breast cancer patients who were consecutively diagnosed and 
treated at the Massachusetts General Hospital between 1985 and 1997. Primary 
tumors from 100 patients with node-negative, invasive breast cancer (median age, 
62.5 years; median follow-up, 11.3 years) were subjected to MammaPrint analysis 
and classified as being at either low or high risk for distant metastasis.
RESULTS: The MammaPrint 70-gene signature displayed excellent NPV as in previous 
studies, correctly identifying 100% of women at low risk for distant metastases 
at 5 years. However, this assay had a lower positive predictive value (12% at 5 
years) than previously observed.
CONCLUSIONS: The MammaPrint assay was originally designed to identify younger 
breast cancer patients at low risk for distant metastasis, who might 
consequently be spared systemic treatment. We show here that the same signature 
has a very high NPV for distant recurrence after adjuvant treatment in older 
breast cancer patients.