For ER-positive breast cancers, chemotherapy decisions are often guided by genomic tests like the Oncotype DX Recurrence Score or Mammaprint.

“if the tumor um is estrogen or are positive we go through a process where we decide whether or not the patient needs chemotherapy and that usually involves um an oncotype DX recurrent score or similar genomic test done on the tumor itself where they look at the patterns of gene expression in the tumor”

“those have been shown to be very powerful at figuring out who does and more importantly who does not need chemotherapy so there's been a huge shift in how we use chemotherapy in ER positive breast cancers over the past 25 years from the time in 1999 when the NCI said every woman who had a 1 cimeter cancer needed chemotherapy to a Time nowadays when we frequently can avoid chemotherapy for most ER positive breast cancers certainly those that are noed negative and many of the ones that are noed positive as well because we understand that based on this genomic test the chemotherapy is just not going to help them do better in the long run”