TREAT ctDNA

Key inclusion criteria

• Female (pre- or postmenopausal) or male, age ≥18 years
• ER+, HER2- breast cancer
• Intermediate to high-risk patients identified by the stage and previous use of CT in the curative setting
• Stage IIB or III and completed adjuvant chemotherapy
• ECOG PS 0-1 (Randomization phase)
• Completed ≥4 cycles of neoadjuvant chemotherapy and resiudal tumor at surgery of ≥ 1cm (≥ypT1c) or axillary node + (ypN+)
• Patients must have received at least 4.5 years and up to 7 years of ET and planned to continue adjuvant ET during ctDNA screening phase
• Previous adjuvant CDK4/6 inhibitor or PARP-inhibitor treatment is allowed
• Available FFPE tumour block with 25mm2 minimum surface from the baseline biopsy or from surgical specimen OR preferably 6-10 unstained slides of 10μm each

Main exclusion criteria

• Suspected recurrent disease
• Prior treatment with any SERD or investigational ER antagonist
• Previous history of invasive BC or bilateral BC