DATO-BASE: DATOpotamab-deruxtecan for Breast Cancer Brain metAstaSEs

This trial (DATO-BASE) is testing an antibody-drug combination called datopotamab deruxtecan (Dato-DXd) in people with HER2-negative metastatic breast cancer that has spread to the brain, to see whether this drug can cross into the brain and shrink or control cancer there. **You may be eligible if...** - You are an adult with confirmed HER2-negative metastatic breast cancer - You have brain metastases (cancer that has spread to the brain) that are either newly diagnosed or progressing after prior treatment - You have at least one measurable brain lesion of 1 cm or larger on MRI - You are able to have an MRI (or head CT if MRI is not possible) **You may NOT be eligible if...** - Your breast cancer is HER2-positive - You have leptomeningeal disease only (cancer coating the brain lining) without measurable brain lesions - You have had prior treatment with datopotamab deruxtecan or similar drugs - You have active autoimmune conditions requiring systemic treatment Talk to your doctor to see if this trial is right for you.