Tissue-agnostic drug approvals: how does this apply to patients with breast cancer?

Precision medicine has provided new perspectives in oncology, yielding research on the use of targeted therapies across different tumor types, regardless of their site of origin, a concept known as tissue-agnostic indication. Since 2017, the Food and Drug Administration (FDA) has approved the use of three different agents for tumor-agnostic treatment: pembrolizumab (for patients with microsatellite instability or high tumor mutational burden) and larotrectinib and entrectinib (both for use in patients harboring tumors with NTRK fusions). Importantly, the genomic alterations targeted by these agents are uncommon or rare in breast cancer, and little information exists regarding their efficacy in advanced breast cancer. In this review, we discuss the prevalence of these targets in breast cancer, their detection methods, the clinical characteristics of patients whose tumors have these alterations, and available data regarding the efficacy of these agents in breast cancer.