Predicting local recurrence using PAM50 in postmenopausal endocrine responsive breast cancer patients.

1008 Background: Breast conservation may lead to increased local recurrence rates compared with mastectomy. We investigated whether genetic expression profiling using PAM50 may predict local recurrence free survival (LRFS) independent of established factors Methods: Tumor blocks from patients randomized within the ABCSG 8 trial comparing tamoxifen with tamoxifen followed by anastrozole after surgery were analysed by the PAM50 assay (Prosigna, NanoString Technologies). Postmenopausal patients with endocrine responsive her2neu negative breast cancer were included. The risk of recurrence (ROR) score as well as biological subtypes (Luminal A and B) were correlated with LRFS. Results: 1,308 patients were analysed. 59% were <65 years, 79% had breast conservation (BCT) followed by radiotherapy and 32% were nodal positive. 72% had a low ROR score, 68% were luminal A while 28% had a luminal B cancer. After a median follow up of 11 years, 34 locoregional recurrences were observed, defined as ipsilateral in breast o...