A phase 2 randomized, double-blind, placebo-controlled trial of endocrine therapy ± radium-223 dichloride (Ra-223) in HER2- hormone receptor+ breast cancer patients with bone metastases.

Abstract

TPS622Background: Bone-metastatic breast cancer (MBC) treatment (tx) is limited. In a phase 2a study of bone-dominant MBC patients (pts), Ra-223, a first-in-class α emitter with targeted cytotoxic effect on bone metastases (mets), reduced bone biomarker levels with favorable safety (Coleman et al. Breast Cancer Res Treat 2014). This study evaluates efficacy and safety of Ra-223 v placebo (pbo), each + endocrine treatment (ET) in pts with HER2- estrogen receptor (ER)+ bone-dominant MBC (NCT02258464). Methods: Eligible pts are pre- or postmenopausal with HER2- ER+ bone-dominant MBC with ≥ 2 bone mets, soft tissue mets, and 1-2 prior symptomatic skeletal events (SSEs) (external beam radiotherapy, pathologic bone fracture, spinal cord compression, orthopedic surgery) who have received ≥ 1 line ET for MBC and are considered appropriate for further ET. Eligible pts must have evaluable disease (RECIST 1.1), be taking bisphosphonates or denosumab for ≥ 1 mo before study tx, have an ECOG score 0-1, and have adequa...