Breast Cancer Index (BCI) and prediction of benefit from extended aromatase inhibitor (AI) therapy (tx) in HR+ breast cancer: NRG oncology/NSABP B-42.

501Background: The BCI HOXB13/IL17BR ratio (BCI-H/I) has been shown to predict endocrine tx (ET) and extended ET (EET) benefit. We examined the effect of BCI-H/I for EET benefit prediction in NSABP...