Do you modify your choice of systemic therapy for localized early stage ER+/PR+ HER2- breast if Mammaprint shows basal subtype?

It would make me want to recheck the ER/PR IHC through another lab to make sure it is truly positive. There are some ER positive tumors (especially low expressors) that have basal transcriptional profiles suggesting a lack of estrogen pathway signaling. If the ER is truly positive and it is >= 10% on IHC, I would still offer endocrine therapy after chemotherapy since we don't have validation for using Blueprint to select patients for endocrine therapy.

I think the first thing to make sure if we are using Mammaprint to guide chemotherapy is:

• Was it sent in a clinically high risk tumor?
• Was the Mammaprint high or low risk?

Assuming the Mammaprint was low risk for a clinically high risk tumor, I do not believe we have data to use the basal subtyping to recommend adjuvant chemo. It would make me want to ensure, as Dr. @Dr. First Last mentioned, that the ER/PR stains are reviewed, potentially on the same block the Mammaprint was sent off to not be missing an ER low or TNBC tumor.