Personalizing endocrine therapy for breast cancer using MRI

Abstract

The introduction of adjuvant systemic therapy (AST) has improved patient outcome in breast cancer. However, as the AST indication has shifted towards including more favorable disease profiles, increasingly more patients are treated with AST who experience a relatively lower survival benefit whilst exposed to the considerable side effects. Current efforts are aimed at identifying patients who do not experience survival benefit and can be spared treatment with AST (and the risk at side effects). However, for endocrine therapy, a subtype of AST, there are no clinically validated options to identify such patients beyond the expression of the estrogen receptor. The aim of this thesis was to investigate whether MRI, and especially parenchymal enhancement of the contralateral breast (CPE), could predict survival and endocrine therapy effectiveness in breast cancer patients. High CPE was previously reported to be associated with improved outcome. The SELECT-study was designed to validate the potential of CPE to personalize treatment and included 1500 patients from 10 centers from the Netherlands. The results showed that high CPE was associated with reduced outcome, opposite as previously reported, and not associated with endocrine therapy effectiveness. Similarly, CPE before neo-adjuvant endocrine therapy (NET) and during NET were associated with outcome after surgery. Additionally, prediction of survival after NET based on CPE performed better than based on MRI characteristics as defined by the BIRADS. Due to the conflicting results, more research is required to elucidate if and what potential role CPE has in the personalization of (neo-)adjuvant treatment in breast cancer patients.