Primary non-adherence to adjuvant endocrine therapy in older women with breast cancer.

285 Background: Adjuvant endocrine therapy (AET) improves survival in hormone receptor positive breast cancer (HR+BC). Challenges with adherence to AET in seniors are well documented; however, there is limited knowledge on primary non-adherence (PNAD). PNAD is defined as non-initiation of a prescribed medication. Our aim is to characterize PNAD rates in women aged ≥ 65 with HR+BC and identify potential predictors, using real-time treatment...