Lapatinib in Metastatic Breast Cancer Resistant to Hormone Therapy

Inclusion Criteria:

• Patients with histologically or cytologically proven metastatic breast cancer.
• Patients with either estrogen or progesterone receptor positivity on the most recently examined tumor biopsy.
• Patients must have most recently been using an anti-estrogen (tamoxifen, toremifene, raloxifene, or fulvestrant) or an aromatase inhibitor.
• Patients must have had either a partial response or better, or stable disease for 24 weeks or longer, followed by disease progression, on the current or most recent hormonal therapy for management of metastatic breast cancer.
• Patients must be enrolled within six weeks of defining disease progression on hormonal therapy.
• Patients must have stopped fulvestrant at least four weeks prior and other endocrine therapy at least two weeks prior to enrollment on study.
• Patients must have either measurable disease or at least one evaluable bone lesion that has not been irradiated. Measurable disease is not necessary.
• Estimated life expectancy of at least 6 months.
• ECOG performance status 0-2.
• Adequate hematologic, hepatic, and renal function.
• Patients must be post-menopausal, or they must be practicing either abstinence or an adequate method of contraception, or their sexual partner must be sterile.
• All patients must be able to swallow, retain, and absorb oral medications.
• All patients must be able to give informed consent indicating that they are aware of the investigational nature of this study.

Exclusion Criteria:

• Patients may not have received an investigational agent within the prior four weeks.
• Patients may not have received trastuzumab within three weeks of study entry.
• Patients may not have had major surgery within the prior two weeks.
• Patients may not have Class III or IV heart failure as defined by the NYHA functional classification system.
• Patients may not have a left ventricular ejection fraction < 40% based on MUGA or echocardiogram.
• Patients may not have uncontrolled brain metastases or leptomeningeal disease.
• Patients may not have rapidly progressive visceral metastases.
• Patients may not have a serious illness or conditions including clinically significant cardiac disease, angina pectoris, serious psychiatric disorder, or an active infection.
• Patients may not be receiving concurrent medications (listed in the protocol) which may interact with lapatinib during treatment with lapatinib.