Exploratory Lapatinib (Positron Emission Tomography) PET Study in Subjects With Breast Cancer

Lapatinib is an anti-cancer drug taken by mouth which inhibits the HER2 protein, overexpressed in some breast tumours. It is not known whether lapatinib passes through the blood-brain barrier, and, therefore, whether it can target secondary tumours in the brain. This study will investigate whether lapatinib does indeed enter the brain. Subjects with HER2-overexpressing breast cancer, with and without brain metastases, will receive lapatinib tablets daily for 8 days. The subjects will also receive lapatinib with a small amount of radioactivity attached on the first and last days of dosing to investigate whether it is taken up by the brain, using positron emission tomography (PET) scans.