NCT02675231

Who might be able to join this trial:

• You have been diagnosed with breast cancer that is both HR+ (hormone receptor-positive) and HER2+ (HER2-positive).
• Your breast cancer cannot be removed by surgery, has come back locally, or has spread to other parts of the body (metastatic).
• You have enough tumor tissue available for testing before joining the trial.
• Your cancer can be measured or tracked using standard imaging methods.
• You have previously received at least 2 treatments specifically targeting HER2 for advanced disease.
• You have previously received a specific drug called trastuzumab emtansine (T-DM1) at some point during your treatment.
• You have previously received a type of chemotherapy called a taxane at some point during your treatment.
• You may have received hormone therapy before, but not fulvestrant.
• You are postmenopausal — either naturally, through surgery, or through medication that suppresses your ovaries.
• Your general health and ability to carry out daily activities falls within an acceptable range (confirm with trial site).
• Your heart is pumping blood effectively enough, with a specific heart function score of 50% or higher.
• Your liver, kidneys, and other organs are functioning well enough to participate.
• If your menopause was brought on by certain medications or radiation, you have had a negative pregnancy test within 14 days before joining and agree to use approved contraception during the study and for 12 weeks after your last dose.
• If you had recent localized radiation therapy, it was completed at least 2 weeks before joining and you have recovered from its side effects.
• You have stopped all previous cancer treatments for the required amount of time before starting the study drug (at least 21 days for certain types, or 14 days for others), and have recovered from their side effects — except for trastuzumab, which may continue.
• You are able to swallow capsules.

Who may not be able to join:

• Your cancer is causing a serious, life-threatening crisis affecting your internal organs (confirm with trial site).
• You have cancer that has spread to your brain or spinal cord and is untreated, causing symptoms, or requires steroids to manage.
• You had major surgery within the 14 days before joining the trial.
• You have previously been treated with a type of drug called a CDK 4/6 inhibitor.
• You have recently received an experimental drug that has not been officially approved, within 14–21 days before joining.
• You have a serious pre-existing health condition that the study doctor believes would make it unsafe for you to participate.
• You have had heart failure with symptoms, a heart attack, or unstable chest pain within the past 6 months.
• You have had certain serious heart rhythm problems or a sudden cardiac arrest within the past 12 months.
• You have a history of another cancer in the past 3 years (skin cancers of certain types or very early-stage cervical changes may be exceptions — confirm with trial site).
• You currently have an active bacterial, fungal, or detectable viral infection.
• You have received a live virus vaccine within the 28 days before joining the trial.
• You have a known allergy or sensitivity to trastuzumab, fulvestrant, or certain related substances used in these medications.

Important: Always verify eligibility with the trial site directly before applying.