Study on Tucatinib with Capecitabine and Trastuzumab for Patients with Advanced HER2+ Breast Cancer

Inclusion Criteria

• Have a confirmed diagnosis of HER2+ breast cancer using specific lab tests.
• If you do not have brain metastases, you must have been treated with trastuzumab, pertuzumab, and T-DM1 before.
• If you have brain metastases, you must have been treated with trastuzumab before.
• Your cancer must have progressed after the last treatment or you cannot tolerate the last treatment.
• Have cancer that can be measured or assessed using standard imaging methods.
• Be in good overall health with an ECOG performance status of 0 or 1, meaning fully active or restricted in physically strenuous activity but ambulatory.
• Have a life expectancy of at least 6 months, as determined by your doctor.

Exclusion Criteria

• Eligible for a tucatinib clinical trial.
• Cancer returned within 3 months after last treatment with capecitabine for metastatic disease.
• History of severe allergic reactions to trastuzumab, capecitabine, or similar drugs, except for mild reactions to trastuzumab that were managed.
• Have received any cancer treatment (except hormonal therapy) or experimental drugs within 3 weeks before starting the study treatment.
• Have unresolved side effects from previous cancer treatments, except for mild hair loss, mild nerve damage, mild heart failure that has resolved, or mild anemia.
• Have significant heart or lung disease.
• Have had a heart attack or unstable chest pain within 6 months before starting the study treatment.
• Have uncontrolled Hepatitis B, Hepatitis C, or other chronic liver disease.
• Have uncontrolled HIV.
• Are pregnant, breastfeeding, or planning to become pregnant.
• Need to take warfarin or similar blood thinners (other types are allowed).
• Cannot swallow pills or have digestive issues that affect medication absorption.
• Have used certain strong medications that affect drug metabolism within a specified time before starting tucatinib.
• Have a genetic deficiency affecting drug metabolism.
• Have had another cancer requiring treatment within 2 years before starting the study treatment.

CNS Exclusion:

• Have untreated brain lesions larger than 2.0 cm, unless approved by the medical team.
• Need to take more than 2 mg of dexamethasone daily for brain metastases symptoms, unless approved by the medical team.
• Have brain lesions needing immediate treatment.
• Have known or suspected leptomeningeal disease.
• Have poorly controlled seizures or worsening neurological symptoms due to brain metastases.